CFC substitutes, not as destructive as the original chlorofluorocarbons, and similar chemicals known as halons continue to wreak stratospheric havoc even today, more than thirty years after the Montreal Protocol. Meanwhile, the amount of yet another significant ozone layer depleter, nitrous oxide, is increasing rapidly in the skies.

In this article, find out everything you need to know about the top 3 causes and effects of ozone layer depletion. Fortunately, solutions exist to the problem of stratospheric ozone destruction. Learn how you can help rebuild the life-sustaining ozone layer and keep it intact.

What is the ozone layer?

Just two pennies thick (0.12 in.) and encircling the Earth at approximately 10-12 miles above it, the ozone layer, also called the ozonosphere, straddles the boundary between the troposphere and the stratosphere in Earth’s atmosphere. It acts as a dynamic filter for the ultraviolet (UV) radiation streaming from the sun.

Approximately half of less harmful, longer-wavelength UV-A rays get a pass. But almost all harmful, shorter-wavelength UV-B and UV-C rays get blocked.

Here’s a diagram that shows where the ozone layer is in the atmosphere in relation to the Earth:

The ozone layer makes life on Earth possible. As science historian Dorothy Fisk said in 1934, the ozone layer is “all that stands between us and speedy death.” The ozone layer is normally thinner at the equator and thicker at the North and South Poles.

When ozone exists in the stratosphere, it offers protection to all life forms on Earth. By contrast, ground-level ozone in smog, spewn by cars, trucks, factories, and power plants, obstructs normal breathing and is associated with higher risk for developing respiratory conditions including asthma.

Named for one of the chemicals that comprises it, the ozone layer contains ozone, a highly reactive (unstable) molecule composed of three oxygen atoms. The chemical formula for ozone is O₃.

First completely described by the British geophysicist Sydney Chapman in 1931, stratospheric ozone exists in a steady state of equilibrium with its diatomic cousin, O₂, containing only two oxygen atoms. This is the form of oxygen that humans breathe.

According to Chapman, the O₃-O₂ conversion constantly makes and remakes the ozone layer, in a dynamic exchange. Originally on Earth, billions of years before humans appeared, microscopic plants in the ocean produced oxygen (O₂) during photosynthesis.

Eventually, the oxygen traveled out into the atmosphere. Once in the stratosphere, short-wavelength UV radiation split the molecules, releasing oxygen free radicals. The oxygen radicals possess the sun’s high energy. Being so unstable, the oxygen radicals react with other O₂ molecules, forming ozone.

In turn, when ozone is struck by UV radiation, it liberates a stable diatomic molecule (O₂) and an oxygen free radical (O) in a process called photodissociation. As an energized radical, O quickly reacts with a nearby O₂ molecule, forming a new ozone molecule. Then when the sun’s rays strike the newly formed O₃, the entire process repeats.

These chain reactions happen continuously in the ozone layer (more appropriately called the O₃-O₂ layer). The global exchange between O₃ and O₂ in the ozone layer is approximately 300 million tons per day.

Here is a schematic that shows the chemical reactions between O₃ and O₂. (Note: The numerical subscripts indicate the number of atoms present in the molecule. When there is no subscript, there is just one atom.)

Besides the ability to block UV radiation, the ozone layer serves another critical function for the Earth. The pressure it exerts allows it to operate like a tight-fitting seal above the troposphere (the atmospheric layer closest to the Earth’s surface). In this capacity, the ozone layer affects Earth’s weather patterns and heat cycles.

Top 3 causes of ozone layer depletion

Ozone layer depletion refers to the situation during the O₂-O₃ inter-conversion in the stratospheric ozone layer (described in the preceding section) when the destruction of O₃ exceeds the creation of O₃. In other words, there is a net loss of ozone in favor of the formation of more O₂.

Until the 1970s, people believed the ozone layer couldn’t be affected by other chemicals. This turned out to be false, as the ozone hole attests (see below).

In the ‘70s, scientists began to investigate how other chemicals could disrupt the delicate balance of chemical reactions in the stratosphere. They were surprised that ozone layer depletion could occur. Once scientists began publicly announcing their discoveries, it set off alarms.

Spurred on by citizens’ panic, some governments placed restrictions on the production and use of chlorofluorocarbons (CFCs), believed to be the major culprits in ozone layer depletion. Others called for more study before taking action, leading to further research into the ozone layer.

Decades of research resulted in conclusive evidence that chlorofluorocarbons, nitrous oxides, and halogens were the top 3 causes of ozone depletion.

1. Chlorofluorocarbons (CFCs)

Chlorofluorocarbons (CFCs) is the name given to a broad class of chemical compounds used as refrigerants containing just three elements: chlorine, fluorine, and carbon. Thomas Ridgley, Jr., a mechanical engineer, and his assistant, chemist Albert L. Henne, invented many of the first-generation CFCs in 1928. They called them Freon.

Similar compounds called hydrochlorofluorocarbons (HCFCs) were invented later.

In 1974, chemists F. Sherwood Rowland and Mario Molina published a landmark paper in the distinguished journal, Nature. They announced their discovery that typically nonreactive CFCs, after spending decades in the troposphere close to the Earth, eventually are carried up into the stratosphere by atmospheric winds.

Like ozone, CFC molecules photodissociate upon being hit by solar ultraviolet radiation. But in this case, chlorine atoms, noted by their chemical symbol, Cl, are freed.

Encountering oxygen free radicals, present from O₃ photodissociation as explained in the previous section, chlorine reacts with them, forming chlorine monoxide (ClO). In the process, the chlorine atoms bind up oxygen free radicals. This prevents them from reforming ozone.

To make matters worse, one molecule of ClO reacts with a second oxygen radical. Diatomic oxygen (O₂) forms in a reaction that absorbs no UV light, leaving chlorine-free to react with yet another oxygen radical.

In other words, it’s as if chlorine hijacks oxygen free radicals, disrupting the normal O₂-O₃ equilibrium necessary to keep the ozone layer intact. While this is happening, solar radiation streams past, heading to Earth.

Here is a schematic that illustrates what is happening to ozone when it encounters a CFC molecule in the stratosphere:

In the stratosphere, the catalytic chain reaction involving chlorine occurs over and over until chlorine eventually encounters a methane or nitrogen dioxide molecule. They react, forming stable, heavier compounds that eventually fall back to the troposphere and land on Earth.

But the damage to the ozone layer has already been done by rogue chlorine from CFCs. In its stratospheric sojourn, a single chlorine atom destroys 100,000 or more ozone molecules. Expressed in another way, one pound of CFCs can destroy 70,000 lbs. of ozone.

Given the million or more tons of CFCs produced every year, Rowland and Marino initially predicted 20-40% of ozone layer depletion was likely if all of the CFCs made it to the stratosphere. At the time of their research, 70% of CFCs were used in aerosol spray cans for all sorts of products such as cooking spray, hair spray, and deodorant. With each spray, you’d release CFCs into the air. So most of them would eventually reach the stratosphere.

Currently, most aerosol sprays do not use CFCs. There are several alternatives including hydrofluorocarbons (HFCs) and carbon dioxide. Today, the major use of CFCs and related compounds like HFCs is in refrigerants and air conditioners. It is also used to fluff up foam and clean electronic parts.

What is the ozone hole?

The ozone hole over Antarctica in the Southern Hemisphere is not really a hole. Rather, it is an area of the stratosphere where the ozone layer has thinned considerably, allowing harmful UV radiation to reach the Earth. It begins to enlarge near the beginning of Antarctica’s spring of every year as explained below.

A similar event occurs in the Arctic, but not as dramatic. 1980s measurements revealed a 40% depletion in the ozone layer in September (the end of the Antarctic winter).

Joseph Farman at the British Antarctic Survey first observed a drastic reduction of ozone in 1981 compared to all the data he had collected since 1956. Skeptical of their veracity, he hid the data, which repeated in the following four years. Finally, in 1985, he published his measurements and shocked the world.

In 2022, the Antarctic ozone hole was approximately 9 million square miles, slightly smaller than in 2021. For comparison, that is more than twice the area of the continental U.S. The ozone hole peaked in size in 2006. Scientists state that the Montreal Protocol, the only international treaty signed by all countries, is responsible for the reduction in the size of the ozone hole. 

Here is an image of it:

The ozone hole appears due to the chlorine chemistry during the frigid polar vortex that settles over Antarctica during its winter. But how does chlorine get to the remote Antarctic?

As described in the preceding section on CFCs, chlorine atoms break away from chlorofluorocarbons (CFCs) in the presence of stratospheric UV radiation. They later attach to oxygen free radicals, leading to ozone layer depletion, in a catalytic chain reaction.

However, chlorine atoms do not immediately cause ozone depletion once they arrive in the stratosphere. In fact, the freed chlorine atoms usually become part of two other chemicals and remain in the stratosphere for some time in those relatively stable forms. These chemicals are hydrochloric acid (HCl) and chlorine nitrate (ClNO₃).

However, in the winter over Antarctica, polar stratospheric clouds form within the whirlpooling winds of frigid air in the polar vortex centered over the South Pole. Under these extraordinary conditions, HCl and ClNO₃ react. One of the major products formed is chlorine gas (Cl₂).

When spring arrives in the Antarctic, the sun’s UV radiation breaks Cl₂ gas molecules apart, liberating chlorine atoms. It is these free chlorine atoms (along with bromine, another halogen) that interfere with the O₂-O₃ equilibrium and deplete the ozone layer. Up to 2-3% of the ozone layer can be destroyed per day by this process.

Here’s a flow diagram that illustrates the entire pathway of ozone depletion caused by the halogens, chlorine, and bromine:

Has the Montreal Protocol fixed the ozone hole?

Although the Montreal Protocol and its amendments, including the most recent Kigali Amendment added in 2016 banning hydrofluorocarbon (HFC) production go far in abolishing the manufacture of ozone layer depleters, much work remains to be done to eradicate all chemicals and practices that deplete the ozone layer.

The Protocol allows the continued use of existing CFCs and does not mandate their removal or destruction. So, in 1995, the year before US production was to end, a multi-million dollar CFC black market emerged. It continues to this day and now includes HFCs.

Further, slow phaseouts of chemicals and rule exemptions slow down the reversal of ozone layer depletion. Additionally, there are some companies illegally producing some of the most ozone-destructive CFCs in recent years. Constant surveillance and enforcement are essential. If this doesn’t happen, the ozone hole could begin to enlarge again.

Furthermore, since ozone-depleting nitrous oxides (see below) are not regulated by the Montreal Protocol, their escalating use could cause further destruction of the ozone layer well into the 21st century and beyond.

2. Nitrous oxides

In 1970, atmospheric chemist Paul Crutzen studied nitrous oxide (N₂O) in the stratosphere. There, the sun’s radiation splits it into nitric oxide (NO) and nitrogen dioxide (NO₂).

Further, in a series of catalytic chain reactions, NO and NO₂ interfere with the O₂-O₃ equilibrium of the ozone layer in the stratosphere, blocking ozone formation. As a result, there is ozone layer depletion.

Here is a schematic showing these reactions:

The major source of stratospheric nitrous oxide is agriculture, especially fertilized soil and livestock manure. (It’s also used in dental offices as laughing gas.)

Unlike CFCs, nitrous oxides aren’t regulated by an international agreement. So, scientists A.R. Ravishankara, J.S. Daniel, and Robert W. Portmann of NOAA’s Earth System Research Laboratory (ESRL) concluded that, left unregulated, nitrous oxide will become the leading chemical depleting the ozone layer in the 21st century. In fact, nitrous oxide emissions are twice as high as CFC emissions today.

Catalytic chain reactions in ozone layer depletion

In working on nitrous oxide chemistry, Crutzen elucidated the general series of chemical reactions that result in ozone layer depletion.

In this article, we describe how chlorine monoxide, bromine monoxide, and nitric oxide serve as the catalysts for ozone destruction in the presence of short-wavelength UV radiation. A fourth catalyst, the hydroxyl radical (OH), produced in polar stratospheric clouds, is believed to play a key role in the formation of the other radicals and in ozone layer depletion.

All catalysts share one major thing in common: they are neither consumed or destroyed in a chemical reaction. Thus, a single catalyst is free to repeat the chain reactions hundreds of thousands of times, resulting in a net loss of stratospheric ozone. This is how ozone depletion occurs. (Note: A catalyst is noted by “R” in the following reaction series from ChemTube3D.) 

R + O₃ → RO + O₂

RO + O → O₂ + R

RO + O₃ → R + 2O₂

Net Reaction (in UV light): 2 O₃ → 3 O₂

Source: ChemTube3D

Crutzen, along with Rowland and Morina mentioned in the preceding section, won the Nobel Prize in Chemistry for their work on stratospheric ozone chemistry and the discovery of the ozone-depleting properties of CFCs and nitrous oxide in 1995.

When announcing the winners, the Royal Swedish Academy of Sciences stated:

“Even though ozone occurs in such small quantities, it plays an exceptionally fundamental part in life on earth. This is because ozone, together with ordinary molecular oxygen (O₂), is able to absorb the major part of the sun’s ultraviolet radiation and therefore prevent this dangerous radiation from reaching the surface. Without a protective ozone layer in the atmosphere, animals and plants could not exist, at least not upon land.”

3. Halons (bromocarbons)

Halons are molecules containing bromine and carbon. Bromine is a member of the chemical family known as halogens, along with fluorine and chlorine.

Since chlorine atoms in chlorofluorocarbons (CFCs) are rapid ozone depleters, you might think that bromine atoms from halons would have the same destructive effect on ozone. Actually, bromine is far worse as an ozone depleter. In fact, one pound of a common halon, called 1211, can destroy 25 tons of ozone.

In the atmosphere, bromine commonly exists in the stable forms of hydrogen bromide (HBr) and bromine nitrate (BrONO₂). However, when exposed to UV radiation, they break apart. Like free chlorine reacts with an oxygen radical to form the highly reactive ClO that causes a net loss of ozone, free bromine atoms do the same thing as BrO. Bromine atoms are 40 to 100 times as effective as chlorine at depleting ozone.

Here are reactions involving both chlorine and bromine showing how ozone is depleted and diatomic oxygen (O₂) is formed. These coupled reactions are responsible for 30-40% of ozone layer depletion in the Antarctic.

Human-made products release up to 60% of all halons in the stratosphere. The use of methyl bromide fumigants and halon fire extinguishers are the major ways bromocarbons cause ozone layer depletion. Halons are regulated under the Montreal Protocol.

Top 3 effects of ozone layer depletion

Ozone layer depletion adversely affects humans, wildlife, marine ecosystems, plants, insects, and agriculture. When the ozone layer is thinned, more harmful UV-B radiation arrives to the Earth’s surface. Furthermore, research in 2007 suggested that more deleterious UV-C radiation, commonly believed to be blocked completely by the ozone layer, was also hitting Earth’s surface. Since then, other scientists have corroborated this conclusion.

1. Human health effects

According to the Environmental Protection Agency (EPA), the four major human health effects from ultraviolet radiation exposure are:

• Skin cancer: As the most common form of cancer, skin cancer affects 20% of people living in the United States. It is also easily preventable. Using sunscreen or avoiding the sun are proactive measures you can take to protect yourself from this carcinogen.

• Premature aging and other skin problems: Up to 90% of all skin changes attributable to aging are actually caused by the sun. UV radiation from the sun causes thick, wrinkled, and leathery skin. A common skin growth called actinic keratosis is a pre-cancer that could develop into full-blown cancer if not removed.

• Cataracts and other eye damage: UV radiation increases the likelihood that you’ll develop cloudy lenses (cataracts) that may lead to blindness if left untreated. Other eye damage includes pterygium (vision-blocking growth of tissue) and macular degeneration. To avoid these problems, wear sunglasses with 100% UV-A and UV-B protection.

• Immune system suppression: Although sunlight stimulates the production of vitamin D in the skin, believed to boost immunity, UV-B radiation is known to suppress the immune system. As a result, skin infections and cancer are more likely to occur.

2. Ocean ecosystem effects

Microscopic marine plants called phytoplankton are the foundation on which all marine food webs depend. Their populations are reduced by UV-B exposure. Consequently, there will be reduced fish stocks. Humans who rely on fish as their major source of protein and/or livelihood will experience malnutrition or economic hardship.

Phytoplankton researchers estimated that a 16% reduction in the ozone layer could result in a 5% die off of phytoplankton. Although 5% may not seem significant, this equals a loss of approximately 7 million tons of fish per year.

UV-B radiation also negatively affects ocean productivity in other ways. For example, photosynthesis by red, brown, and green benthic algae is significantly reduced by solar radiation. Since marine photosynthesis is responsible for producing more than half of the oxygen that humans breathe, ozone depletion is a real concern when it comes to human survival.

As previously mentioned in the section on the ozone hole, early spring is when the ozone layer is the thinnest. This happens to be the time when the early developmental stages of fish, shrimp, crabs, amphibians, and other animals occur. During these critical stages, organisms are highly sensitive to adverse environmental effects. UV-B radiation exposure interrupts normal development as well as the reproductive capacity of adults, resulting in greater mortality and smaller offspring.

3. Agricultural losses

Plants are adversely affected by UV-B radiation in several ways. Research shows some of these ways are:

• Reduction in leaf area
• Decreased stem growth
• Inhibited photosynthesis
• DNA damage
• Change in the time of flowering
• Reduction in the number of flowers

Studies done on the most common agricultural species, such as rice, soybeans, winter wheat, cotton, and corn, indicate that overexposure to UV-B reduces their size, productivity, and quality. If this occurs, food insecurity or famine could result.

Agriculture is also negatively affected by the climate crisis. With global heating comes disruptions in plant flowerings. When insects aren’t present to pollinate crops that flower out of sync with insect life cycles, crop productivity plummets.

Furthermore, several chemicals known to deplete ozone, including CFCs and nitrous oxide, are potent greenhouse gases. In effect, agriculture, on which human civilization depends, is served a double whammy.

It is difficult to determine whether crop losses are directly due to global heating, or specifically due to ozone depletion. To ensure crop productivity and quality, the elimination of CFCs and nitrous oxide will help curb the climate crisis, and preserve the ozone layer as well as biodiversity.

Top 3 solutions for ozone layer depletion

There are numerous actions that governments, corporations, and private citizens can take to prevent ozone layer depletion. Here are the top 3 solutions to ozone layer depletion.

1. Use alternatives to ozone layer-depleting chemicals

Since CFCs, halons, and nitrous oxide are commonly used or produced in most countries, you can begin to reduce your dependence on them through research to assess all the ways these chemicals directly or indirectly affect your life today. Industry is searching for replacements (with less ozone depleting potential) and alternatives (with no effect on the ozone layer) all the time, so it’s necessary to stay informed.

Note: Products or services labeled “non-CFC” or “ozone layer-friendly” often contain chemicals that destroy the ozone layer to a lesser degree than CFCs. So, you may choose to opt out.

Here are some ways that you can limit your personal contribution to ozone layer depletion.

Air conditioning

Today, most coolants are hydrofluorocarbons (HFCs). Once thought to be non-ozone layer depleting, they have been found to be ozone-damaging like their CFC cousins.

As a private citizen, you can eschew conventional air conditioning in your home and car (if you own one). Instead, rely on natural methods to stay cool. These include drinking cold water, taking cold showers, using ceiling fans or opening windows when it’s cooler outside, keeping windows shaded when it’s hot outside, or planting trees around your home.

If you work in an air-conditioned office, you can request that the thermostat be set at 82℉ or higher. Wear light, loose cotton clothing, and keep an iced beverage close by.

Fire extinguishers

Although production of halons is now banned, they are still used. A common replacement is hydrofluorocarbons (HFCs). These do not deplete the ozone layer as much as CFCs, and they are powerful greenhouse gases. Some may have up to 14,000 times the warming potential of carbon dioxide. By their very nature, they are gases made to be released to the environment during firefighting.

Incidentally, carbon dioxide is an alternative material used in fire extinguishers. Investing in a home sprinkling system is an alternative way to protect yourself and your home in case of fire.

You may find fire extinguishers that use recycled halon. Contact the Halon Alternative Research Corporation (HARC) for more information. They may be able to help you recycle your used fire extinguisher (with residual halon still inside).

Polystyrene (Styrofoam)

Foam cups and containers, as well as household insulation, are usually made with CFC replacements today. Note that they have a reduced ozone layer depletion potential.

You could consider eco-friendly home insulation instead. As for cups and containers, try glass or metal.

2. Practice and consume food grown by regenerative (non-industrial) agriculture

If you’re not a farmer, the most effective thing you can do to avoid contributing to nitrous oxide emissions that head to the stratosphere (unlike those in smog that stay in the troposphere) is to stop supporting industrial agriculture. Choosing an all-organic diet, grown, by law, without synthetic fertilizers and pesticides, is key. Although organic fertilizers like mulch or compost contribute nitrous oxide, too, it’s not as bad compared to what synthetic fertilizers do. Since manure also contributes to nitrous oxide emissions, going vegan (no meat or dairy) is ideal.

Farmers who wish to reduce nitrous oxide emissions from their profession could transition to regenerative agriculture. With a focus on restoring soil health through minimal disturbance, indigenous knowledge, carbon sequestration, cover cropping, planned grazing, and enhanced biodiversity, regen ag holds promise as a way to safeguard the land for future generations.

You can get involved by supporting food products with regenerative organic certified labels. In 2023, as Congress writes the next Farm Bill, establishing policy for the next five years, sign the petition to give regen ag a prominent place in U.S. agriculture.

3. No flying

There has been speculation about creating a fleet of supersonic jets as recently as 2020. But, so far, it is considered cost prohibitive. The jets would dump nitrous oxide and water vapor (source of hydroxyl radicals, another catalyst) directly into the stratosphere. So, these jets would undoubtedly deplete the ozone layer.

Subsonic passenger planes produce nitrous oxide, but it likely stays in the troposphere where it creates the pollutant, ground level ozone. Nitrous oxide is a powerful greenhouse gas and contributes to the climate crisis. For this reason, abstaining from flying to reduce your personal carbon footprint is an important way to do so.

Key takeaways on ozone layer depletion

Without the ozone layer encircling the Earth 10-12 miles above it, life as we know it would not exist. In constant flux from the chemical reactions converting diatomic oxygen (O₂) to triatomic oxygen (O₃) and vice versa, the wispy belt just two pennies thick reflects harmful ultraviolet (UV) radiation back into space.

Chlorine in chlorofluorocarbons (CFCs), other halogens like bromine, and nitrous oxide interfere with the O₂-O₃ chemical equilibrium in the stratosphere as catalysts in a series of chain reactions. In fact, the catalysts, when bonded to oxygen radicals, effectively halt the process of net ozone formation. Lacking an ozone filter, harmful UV-B and UV-C rays travel to Earth unobstructed.

As if this wasn’t bad enough for life on Earth, CFCs are powerful greenhouse gases. As such, they contribute substantially to the climate crisis.

Today, increased release of nitrous oxide, another potent greenhouse gas, is causing significant disruption of the O₂-O₃ equilibrium in Earth’s stratosphere. Consequently, ozone layer depletion is still occurring. Nitrous oxide is formed during the manufacture and use of synthetic pesticides and fertilizer for industrial agriculture.

The effects of ozone layer depletion are nothing short of catastrophic. Increased cancer rates and cataracts in humans occur from UV-B exposure. Oceanic phytoplankton populations, responsible for most of the oxygen that humans breathe, plummet from UV-B exposure. Agricultural crops wither, leading to food insecurity and potentially famine.

Solutions to ozone layer depletion require system-changing adjustments to several industries supporting 21st century lifestyles in rich countries like the USA. The air conditioning sector must stop production and use of all CFCs and their chemical cousins in refrigerants. Agribusiness must stop manufacture and application of synthetic pesticides and fertilizer.

If you’re an individual striving to lead a sustainable lifestyle, you can help prevent ozone layer depletion by not relying on conventional air conditioning and agriculture. Transition to alternative ways to keep cool. Grow your own food organically or support farmers practicing regenerative agriculture.

Above all, demand that your governmental representatives take steps to write, enact, and enforce policies that require the air conditioning, refrigeration, and agricultural industries to follow ozone layer-friendly practices. Raise awareness of these problems through public protest. Encourage your friends and family to get involved.

It’s only when the necessary changes summarized here occur on all these levels that ozone layer depletion will permanently end, and the related climate crisis can be somewhat offset.

They are all critically endangered species according to the International Union for Conservation of Nature (IUCN) Red List. This means they are facing serious environmental pressures that can soon push them over the edge to extinction in the wild.

The 42,100 species currently threatened with extinction represent only a tiny fraction of all species currently existing on planet Earth. Biodiversity is the term that includes all of nature’s species abundance. Today, biodiversity faces multiple threats.

In this article, we explore the statistics, facts and considerations relating to the top ten threats to biodiversity. Hopefully, this information will motivate you to help reverse course on these top 10 threats to biodiversity before it’s too late. Learn how below.

What is biodiversity?

Millions of years of evolution have fashioned a wide array of life forms, known as biodiversity (contraction of biological diversity or biotic diversity). Spanning all five taxonomic kingdoms of living things, scientists estimate that there may be up to one trillion species on Earth.

More conservative estimates range from 5.3 million to 8.7 million. By locating markers unique to a particular groups’ DNA (genetic) samples, scientists declare taxonomic classifications.

These varied life forms also possess definitive but invisible genetic diversity in their DNA. When the genetic diversity between individuals or distinct populations is great enough, scientists divide them into different species. In cases where there is much genetic overlap but not enough to warrant a new species declaration, biologists may make subspecies designations.

What is the sixth mass extinction?

Most scientists believe that life on Earth is currently undergoing a sixth mass extinction. This means there is a large number of distinct biological species disappearing from the planet in a short time frame. The current dieoff is comparable in scale to those of past geologic periods, making it a discrete occurrence.

To determine whether the current biodiversity loss is a distinct biological event of accelerated proportions, scientists published a 2015 article assessing the data on vertebrate extinctions. They analyzed the numbers against a background rate of extinction of two mammal extinctions per 10,000 species per 100 years. This assumption is twice as high as the commonly accepted background rate of extinction.

The researchers concluded that extinctions are happening up to 100 times faster now compared to the baseline. Other research teams, using DNA studies as well as the fossil record, recalculated a lower historical background rate of extinction. Using it, they placed today’s extinction rate at 1,000 times faster than at any time in Earth’s history.

As scientists doing this research proposed, huge population shrinkages and range losses of even “species of low concern” (i.e., those not threatened or endangered as defined by the IUCN) indicate that something different is going on in the current extinction.

Many dwindling animal and plant populations around the world signal the human causal nature of this biological event unlike all the other of Earth’s mass extinctions.

In fact, a 2022 World Wildlife Fund report concluded that since 1970, there’s been an average decline of 69% in vertebrate populations across the globe. Here are some examples from the Report:

• 83% loss in freshwater fish
• 94% decline in wildlife in Latin America and the Caribbean
• 71% reduction in sharks and rays

Due to various environmental pressures (threats to biodiversity), threatened or endangered species on the IUCN Red List are at risk of going extinct in the wild this century.

Here is a breakdown of the current status of the 42,100 species (28% of all assessed species) threatened with extinction:

For the vanishing populations of threatened or endangered species still on Earth, corrective action to eliminate threats to biodiversity must occur now or experts predict the escalating threats will cause great numbers of extinctions within decades.

Here is a table listing all mass extinctions to date with their believed causes:

During today’s sixth mass extinction, experts currently believe up to 150 species are going extinct every day. And that’s counting only the species we know of. Biologists estimate there are countless more species in existence. They are uncatalogued, possibly disappearing before scientists have a chance to discover them.

What is a biodiversity hotspot?

An idea developed by ecologist Norman Myers in 1988, biodiversity hotspots are regions with a great variety of plant species that are undergoing extreme environmental stressors such as deforestation.

The specific criteria are:

• Contains 1,500+ species of vascular plants found nowhere else on Earth
• 70%+ reduction in native vegetation

To indicate how minimal these criteria are, some of today’s biodiversity hotspots contain over 15,000 native plant species and have undergone a 95% habitat loss. The list includes the tropical Andes, Wallacea, Caucasus, and the coastal forests of Eastern Africa.

The map below shows where the biodiversity hotspots are:

What are the top ten threats to biodiversity?

The top ten threats to biodiversity are human behaviors, corporate practices, or governmental policies that make it difficult for other species to survive on Earth. Those listed below are inter-connected. Some of them exist in cause-and-effect relationships. The descriptions that follow highlight the major connections.

It is difficult to list the threats to biodiversity definitively in order of priority. Different criteria would alter the order. Those biodiversity threats with the greatest global impact appear closer to the top of the list. The first three fall under the general category of habitat loss.

1. Deforestation

Cutting down intact forests to make way for crops, roads, or buildings is called deforestation. By far, cutting down forests for agriculture is the major reason for this land use change. Global deforestation peaked in the 1980s, but there is still a lot going on.

To find out where deforestation is occurring anywhere in the world, the interactive tools on Global Forest Watch are useful.

Deforestation is not the same as net forest loss. The difference between deforestation and any new forest that has been planted or restored equals the net loss in forest. Since 2010, the Earth has had a net forest loss of 4.7 million hectares per year. According to the Food and Agriculture Organization, the deforestation rate is 10 million hectares/yr.

Here’s a helpful chart to show how humans have already cut down over 33% of the world’s forests over time.

Deforestation effect on biodiversity:

Human encroachment on wildlife habitat forces animals to flee their homes. If other natural homes aren’t available, animals die. When deforestation is common, wildlife may resettle closer to humans.

Deforestation leads to greater proximity of wild animals with humans. The spread of zoonotic diseases, jumping across species to people, becomes more likely. This is a leading hypothesis on how the SARs viruses, including the one that causes Covid-19, reached humans. Since they present new challenges to human immune systems, it’s easy to see how global pandemics can spread.

2. Industrial agriculture

Closely related to deforestation, industrial agriculture is a unique threat to biodiversity. The intensification of food production on a global scale for a burgeoning human population demands that more and more land must be cleared for crops (33% of all land) or pasture for grazing cattle (66% of total land surface).

So far, 38% of all land surface on Earth is devoted to agriculture. Wetlands are also filled for agricultural and other purposes at a rate three times faster than forests are being cut down. Six states in the United States have 85% or more of their wetlands cleared for agriculture. California, an agricultural powerhouse, has up to 91% of its wetlands converted for crops.

Aquaculture, the intensive raising of fish and seafood for human consumption, is the fastest-growing segment in animal agriculture, especially along the coastlines of many countries. Shrimp farming in particular resulted in the destruction of up to 50% of mangrove forests in the 1970s-90s. Important carbon sinks, mangroves draw down carbon from the atmosphere so it won’t contribute to the climate crisis.

Industrial agriculture’s effect on biodiversity:

The United Nations Environment Programme stated that up to 86% of all species at risk for extinction are threatened by agriculture, which they refer to as the primary driver of biodiversity loss. Up to 40% of all species live or mate in wetlands. Without habitat, species go extinct. In studies on mangrove losses and biodiversity, 70 plant species were in decline. Eleven of those were threatened with extinction.

3. Livestock production

As a category of industrial agriculture, rearing animals for food is a specific threat to biodiversity. To satisfy a growing human population’s desire for meat, livestock production is intensive. Whether it’s raising greater numbers in smaller spaces, or rearing bigger animals more quickly, livestock consume huge amounts of natural resources, especially land and water for the crops to feed livestock. This means there are fewer wild animals and plants remaining in those converted areas.

A 2015 study looking at trends in land use concluded that the land needed to support livestock for the estimated human population in 2050 was up to 50% greater than the current land allotment for livestock production in those countries. That growth would occur on 15 biodiversity hotspots where land would need to be converted. As a consequence, biodiversity would dramatically decline.

Effect of livestock production on biodiversity:

Besides the projected effects noted above, global livestock production is the third largest emitter of greenhouse gases driving the climate crisis. Cattle represent 65% of those emissions, producing 44% of the methane coming from livestock production. Livestock production threatens biodiversity, which depends on a stable climate to flourish.

4. Overfishing

The fishing industry is responsible for the marine equivalent of industrial food production. Termed overfishing, the removal of individuals of a species at a rate greater than what can be naturally replenished is causing havoc in marine ecosystems.

With huge, mechanized nets trawling the deep seas — including the ocean floor — approximately 40% (63 billion pounds per year) of all live hauls is bycatch (waste). Noncommercial species are discarded.

As their populations shrink, marine species are threatened. The Marine Stewardship Council states that approximately 35% of global fish stocks are being rapidly depleted. Presently, the IUCN estimates that one-third of all sharks, rays, and chimaeras are at risk of extinction because of overfishing. Little to no regulation of the fishing industry on the international level makes saving marine species very challenging.

Overfishing effects on biodiversity:

Overfishing causes changes in species richness in food webs, often including key predator species. Likewise, it results in changes in species composition, meaning some species are under- or overrepresented. When these changes become too extreme, marine ecosystems lose their ability to function. The production of oxygen — 50-80% of all oxygen on Earth — could be compromised. So, too, could the oceans’ ability to sequester carbon, acting as a brake on the climate crisis.

5. Mining

Lithium, cobalt, copper, and cadmium are just a few of the metals that must be mined to meet the exponential demand for everything from electric vehicles to solar panels and wind turbines, as well as all handheld electronic gadgets. Analysis shows that impacts on biodiversity occur on several levels: site, landscape, regional, and global. These impacts may directly (through extraction) or indirectly (via supporting industries) impact species.

Mountaintop removal for coal mining is another type of mining. A study revealed a 40% loss in aquatic species due to mountaintop removal.

There are also newer industries for deep sea mining for mineral extraction as well as for fish and seafood. All forms of mining threaten biodiversity by eliminating animal and plant habitat.

Mining effects on biodiversity:

Similar to the projections of livestock production, research forecasts more mineral extraction in areas possessing great biodiversity (hotspots). Usually, there is significant environmental damage at mining sites. Species are not always able to cope, and might perish.

6. Climate crisis

Climate crisis refers to the human-caused increase over the last 200 years in atmospheric greenhouse gases resulting in an unstable climate. In contrast to having four distinct seasons and a normal water cycle, the world is experiencing, for example, extreme drought, massive flooding, heatwaves, bomb cyclones, and wildfires. According to United Nations experts, the climate crisis is the worst existential emergency ever faced by humankind. Similarly, as humans die or migrate in response to the climate crisis, so do other species.

Effect of the climate crisis on biodiversity:

In most cases, biodiversity loss is an effect of the climate crisis since many species are unable to adapt to climatic changes in just a few decades. Without functional ecosystems maintained in part by species diversity, it will be increasingly difficult for humans to survive, too.

7. Plastic pollution

Made from fossil fuels, plastic is destroying the planet and threatening its biodiversity just as the greenhouse gases produced by the fuels’ burning are. It is doing so in different ways.

Plastic pollution is clogging waterways all over the world, eventually collecting into massive gyres at five places in oceans and seas around the world. Indestructible, some plastic degrades into microplastic, now eaten and breathed in by humans, including fetuses as the graph below shows.

The 19% of plastic that is incinerated contributes to air pollution, the silent killer of seven million humans every year. Wildlife is easily caught up in the one million tons of ghost gear abandoned by the fishing industry every year, composing 10% of all ocean plastic pollution. Parent birds feed it to their young. Other animals ingest it in place of food. Becoming malnourished over time, they die.

Effect of plastics on biodiversity:

Biodiversity has always been adversely affected when animals get tangled in plastic netting or stuck in plastic containers. They perish, leading to the species demise when it happens too often. Logically, more plastic in waterways — as predicted for coming decades — will lead to heightened biodiversity losses.

Recent research shows that animals are ingesting and breathing microplastics. Plants take them up by their roots. All of the effects on biodiversity aren’t known as this is a relatively new phenomenon. However, one study noted some species suffer microbiome disruptions and tissue abrasions leading to outbreaks of opportunistic bacteria. If individuals weaken and die, species could perish.

8. Pesticides

Along with synthetic fertilizer, pesticides have made it possible for industrial agriculture to expand and feed billions of people in a few decades. Made from fossil fuels, pesticide production necessitates the further expansion of that industry, just like the plastics industry does. In this way, pesticide — and plastic — manufacture contributes to the climate emergency.

Pesticides are applied over the land. Runoff sends them into waterways. So, both terrestrial and aquatic species are harmed. In cases of endocrine-disrupting pesticides, male amphibians undergo chemical castration and feminization. Pesticide interference on fecundity results in smaller populations. With time the species could disappear.

Effect of pesticides on biodiversity:

An experimental study in rearing ponds showed that pesticides combined with other environmental stressors decrease biodiversity in invertebrate and large insect species by 15% and 77%, respectively. A comprehensive review of 400 studies revealed that common agricultural pesticides reduced biodiversity in soil invertebrates including earthworms, beetles, and ground-nesting bees, in 71% of all cases.

Without healthy soil, especially in a climate crisis, crop yields will be reduced. Malnutrition or starvation in humans and other species could result.

9. Invasive species

Plant, animal, and microbial species that aren’t indigenous to an area are called invasive. Sometimes they are introduced intentionally to eliminate perceived pests. Others arrive by accident. Invasive species dominate an area quickly, wiping out native species. Because of their tenacity, it is difficult to eradicate invasives completely. As a result, they threaten native biodiversity with extinction.

Effect of invasive species on biodiversity:

Invasive species hinder the growth of native species through competition for limited nutrients, sometimes acting like predators. They change the ecosystem to the natives’ detriment on a local level which could easily spread to a regional level if the invasive species isn’t controlled. It is difficult to manage invasive species’ effects on biodiversity. One research team suggested that beside controlling the invasives’ reproduction, active regeneration of a compromised ecosystem with native species is essential.

10. Human overpopulation

In 2022, the human population passed 8 billion. To make space for everyone, urban and suburban sprawl dominated the landscape. This meant further encroachment on wildlife habitat, paving it over with fossil fuels (asphalt) and concrete. Native animals and plants struggle to find a place to live.

To feed the people, industrial agriculture expanded further into natural ecosystems, chasing animals out. Many species went extinct as the graph below illustrates.

Wild animal species were brought into closer contact with humans, easing the crossover of new viruses. Synthetic pesticides and fertilizers accelerated food production, but their production contributed to the climate crisis. In the environment, the chemicals harmed wildlife.

Effect of human overpopulation on biodiversity:

Besides all the effects above, human overpopulation in today’s capitalist economy results in overproduction and overconsumption of goods. The natural resources needed for this economic system to succeed are dominated by humans. Other species can’t obtain adequate land or waterway (habitat), or food. What remains may be polluted. So, they become threatened or endangered, and finally may go extinct.

Why should you care about threats to biodiversity?

There are three main reasons why you should care about threats to biodiversity.

1. Human civilization depends on biodiversity for its survival

For example, a wide diversity of pollinators is responsible for over 60% of all crops. Heirloom varieties of fruits and vegetables strengthen the gene pool of those species, keeping them vibrant to ward off disease. Many medicinal plants have not been fully studied, so humanity would lose potential cures. Threats to all these forms of biodiversity endanger human civilization.

2. Biodiversity enriches the human experience

There is a synergy to natural ecosystems that is more than the sum of its parts. To appreciate its beauty, all species living harmoniously are necessary. Additionally, an individual of each species has a unique place and role to play for the proper functioning of their ecosystem. Once species are removed by extinction from the ecosystem, the entirety is in jeopardy of dying. That represents a natural loss from which humans can no longer receive inspiration, knowledge, or wisdom.

3. Biodiversity has intrinsic value

In the first two ways, biodiversity is a means to humans’ ends. But you can also view biodiversity as an end in itself. When you do, biodiversity has intrinsic value. On a practical level, this means biodiversity, and all the species that compose it, has a right to exist in their ecosystem just as humans do. Threats to biodiversity, which can cause species extinction, make it difficult for species to exercise their right. Thus, humans are morally responsible to eliminate the risks caused by the threats to biodiversity so all species may co-exist and thrive.

Some experts state that only economic degrowth — as opposed to growth — can eliminate threats to biodiversity and respect its intrinsic value. Their reasoning is based on the principle that you cannot have infinite growth on a finite planet. If you try and irrevocably degrade biodiversity, it will be gone forever.

“Wildlife is something which man cannot construct. Once it is gone, it is gone forever. Man can rebuild a pyramid, but he can’t rebuild ecology, or a giraffe.” 

– Joy Adamson, naturalist

What you can do to reduce threats to biodiversity

Ultimately, reducing threats to biodiversity requires systemic changes in many industrial practices and government policies in place today. Although one person cannot reform everything, collective action of millions of people following the five recommendations below can create the necessary changes in both industry and government to preserve biodiversity.

So, besides following the recommendations below, encourage all your friends and family to get on board! Do the same at work and school. Raise awareness among your neighbors and acquaintances via thought-provoking conversations that you initiate on the subjects mentioned in the following suggestions.

Finally, writing letters to the editor of your local newspaper, attending community or local government meetings, or even running for public office yourself, are other ways to generate interest in reducing threats to biodiversity and actually accomplish it.

Top 5 recommendations for an individual to help reduce threats to biodiversity

Encompassing all aspects of daily living, the five recommendations below represent steps that, if adopted by the majority of people, would significantly ease the top 10 threats to biodiversity. Adopting the lifestyle depicted through these five suggestions is a public testimony to your conviction that biodiversity matters and that other species have a right to exist in their native habitats and ecosystems.

1. Choose an organic, vegan diet

Adopting an organic, plants-only diet means nothing you eat or drink requires deforestation, livestock production, overfishing, or pesticides. By choosing this lifestyle intervention, you are not contributing to four major threats to biodiversity (see list above).

2. Establish a native plant, pollinator-friendly, no-mow lawn, and garden without synthetic fertilizer or pesticides

Most lawns today are treated heavily with synthetic fertilizers, contributing to water pollution, climate crisis through nitrous oxide production, and reduced capacity for soil to sequester carbon. The production of synthetic pesticides from fossil fuels also contributes to the climate crisis. Their application on lawns is decimating bees and other pollinators. Invasive species take over, killing native plants.

By planting a no-mow lawn, you won’t need to mow, an act that contributes to the climate crisis through carbon emissions of fuel or those that went into producing the battery in electric mowers. Adopting this lifestyle choice means you personally reduce five threats to biodiversity.

3. Avoid buying plastic products

Plastic is solid fossil fuel, the burning of which contributes to the climate crisis. In the United States, less than 5% of plastic is recycled. Most of the rest is landfilled or incinerated, contributing to soil, water, and air pollution. However, 14 million tons of plastic enters the ocean every year day, where it interferes with marine life in many ways, reducing populations. A plastic-free life means you’ve reduced two threats to biodiversity.

4. Limit the amount of consumer goods you purchase

Capitalism thrives on overconsumption of inexpensive goods. Manufacturing them with cheap plastic, made of fossil fuels, in factories run on fossil fuels is detrimental to biodiversity. Deforestation to clear land for more factories and to make wood products (furniture, paper) also occurs as huge corporations expand even further. Any consumer good that runs on batteries necessitates mining for minerals. Limiting the consumer goods you purchase equates to a personal reduction in four threats to biodiversity.

5. Participate in public protests to demand governments make and enforce laws intended to reduce biodiversity threats and protect species

To express your disagreement with accelerating biodiversity loss and your renunciation of all ten threats to biodiversity, participation in public protests is recommended. When large enough numbers of people step out together, on a regular basis, you’re setting the stage for systemic change in industry and government to occur. When you do, voluntary agreements like that from the 2002 COP15, to respect the rights of nature and preserve 30% of all land and waterways for biodiversity, may become mandatory.

Are threats to biodiversity related to the climate crisis?

In most cases, biodiversity loss is an effect of the climate crisis. Many species are unable to adapt to climatic changes occurring in their natural lifespans. They have evolved over millions of years to fit in a very particular niche in their ecosystem. It may take just as long for a species to “adapt” to the climate crisis — if that’s even possible. Viewed in this way, the climate crisis is one of the 10 major threats to biodiversity.

The seasonal availability of a food source during migration, or the lengthy winter for dormancy or hibernation, are just two examples of how climate impacts a species’ niche. Timing is carefully orchestrated. When synchronicity fails, species move toward a precipice of collapse, just like the global climatic system is doing right now.

If a species’ niche is upset due to rapid climatic changes, individcduals perish. If this happens to most in a population, regional extinctions occur. Total species extinctions may follow.

How are biodiversity loss and the climate crisis “two sides of the same coin”?

When experts describe the climate crisis as the flip side to biodiversity loss, the ten threats to biodiversity explained here contribute to the climate crisis as well as result in species or ecosystem diversity loss. In other words, the threats to biodiversity can be contributing causes of the climate crisis just as the climate emergency causes biodiversity loss.

Interestingly, some efforts to halt the climate crisis, such as massive tree plantings or the creation of bioenergy, could accelerate biodiversity loss. There is no doubt that there are many inter-connections as well as reinforcing or antagonistic relationships between the climate crisis and biodiversity loss.

What are co-extinctions and their impact on biodiversity?

New research modeled the likelihood of “co-extinctions” as part of extinction cascades in a given ecosystem. Species that depended on another species for their own survival also went extinct following the extinction of that species. 

Examples include flowers that lose their pollinator insects or predators that lose their prey. In these and similar cases, the climate crisis is the primary cause of the secondary extinctions. 

The scientists predicted that up to 34% more species will go extinct compared to the number from studies that do not take co-extinctions into account. This means 10% of land animals could disappear from particular regions by mid-century. Almost 30% could vanish by 2100. The new modeling more than doubles earlier predictions.

Key takeaways on threats to biodiversity

In 2021, 23 species were declared extinct in the United States. Today, estimates place it at one species going extinct somewhere in the world every ten minutes.

Scientists believe that because of the 10 human-caused threats described in this article, species are undergoing the sixth mass extinction. These major threats to biodiversity include:

• Deforestation
• Overfishing
• Livestock production
• Climate crisis
• Pesticides

The underlying cause of the top ten threats to biodiversity is the belief that economic growth is the highest good a society can achieve. Thus, nations and corporations seek to increase their gross domestic product (GDP) without including environmental costs. They usually do not regenerate damaged or destroyed ecosystems properly — if at all.

Some experts believe the threats to biodiversity can be eliminated or reduced in the time needed to save many species only if degrowth becomes the new economic norm.

The actions individuals can take to help lessen the threats to biodiversity include:

1. Choosing an organic, vegan diet
2. Establishing a pollinator-friendly lawn and garden
3. Avoiding plastic products
4. Limiting the amount of consumer goods you purchase
5. Participating in public protests to demand governments make and enforce laws intended to reduce biodiversity threats and protect species

Not so fast.

In this ultimate guide to bifacial solar panels, you’ll find out everything you need to know about these two-sided solar marvels. 

With this knowledge, you’ll be able to make an informed decision about whether bifacial solar panels are right for you.

What are bifacial solar panels?

Bifacial (two-faced) solar panels (BSPs) are a type of photovoltaic (PV) module that captures solar energy on both its top and bottom sides. The front side facing the sun absorbs direct sunlight. The back end catches the direct rays falling around the panel and the diffuse sun rays, both of which are reflected off of the ground. The lighter the ground’s surface, the greater the reflection. This phenomenon is called the albedo.

Below is a schematic of a bifacial solar panel and how sun rays reach it:

By contrast, monofacial (one-faced) solar panels transform solar radiation into electrical energy from solar cells located on their top side only.

Since Bell Labs began experiments in 1954 followed by the first patented design in 1960 for a bifacial solar cell, BSPs have gained popularity only recently as part of the clean energy transition away from fossil fuels. It was the invention and commercialization of PERC cells in this century that substantially increased the efficiency of BSPs and led to their wider utilization. (More on PERC below.)

Today, BSPs are primarily used for utility-scale generation of solar energy. For example, one of the largest bifacial solar systems in the United States was built in Georgia in 2019. It supplies clean energy to 30,000 households.

How do bifacial solar cells capture light energy?

The top side of bifacial solar cells (BSCs) capture direct rays of light energy in the same way that monofacial solar cells do. However, the back end catches the reflected light energy that monofacial solar cells cannot absorb as well. 

In conventional monofacial mono- and polycrystalline solar cells, some direct light energy goes through the solar cells. It is lost as heat. In theory, if there were another solar cell on the back, it could possibly absorb the lost energy before it dissipates as heat.

There is also direct light energy that arrives around the solar module and is bounced off of surrounding surfaces. Also, diffuse light on cloudy days is present. Monofacials may absorb some of these light forms.

Bifacial solar cells, on the other hand, specialize in capturing the reflected and diffuse light energy. They perform this feat most efficiently when that light is reflected off of a light-colored surface, (for example, a flat white roof or desert sand), and passes through the transparent back sheet or glass. 

This is called the albedo effect. The light rays enter the rear-facing solar cells where their radiant energy can be converted into electricity. 

What do bifacial solar panels look like?

Although there are many different types of bifacial solar cells that do the heavy lifting in converting the sun’s radiant energy to electrical energy, all bifacial solar panels look very much the same. 

Generally, they are slimmer than their monofacial counterparts. In fact, they resemble thin film solar panels more than conventional, bulky mono- or polycrystalline solar panels set in metal frames.

However, bifacial solar panels are usually heavier than mono- and polycrystalline monofacial solar modules because they often have tempered glass on both sides rather than just on the front side. A clear back sheet may be substituted for the glass in some panels.

BSPs are usually heavier even if they are frameless which many are. By comparison, monofacial modules are always encased in metal frames and have a solid metallic backing that prevents light from entering through the underside.

What is the major difference between monofacial and bifacial solar panels?

The major difference between bifacial and monofacial solar panels is that BSPs do not have a solid metal back like monofacial panels have. Instead, they rely on a metallic screen (grid) printed on the silicon wafer for electrical conduction. 

Traditional monofacials with a solid metal backing have aluminum back surface field solar cells referred to as Al-BSF. Al is the chemical symbol for aluminum. You will see both of these shorthand names in some of the diagrams in this article.

Instead of a solid metal sheet, bifacials are made with a highly conductive, although expensive, silver paste for electrical transmission. Silver is noted by its chemical symbol, Ag, in many solar cell diagrams in this article.

How are bifacial solar panels made?

Crystalline silicon (c-Si) bifacial solar panels (BSPs) are made just like traditional mono- and polycrystalline monofacial solar panels are constructed with the addition of two extra steps. These additional steps are required to preserve the solar cells’ efficiency and protect the solar cells on the bottom side.

In her doctoral dissertation on BSPs, Claudia Duran summarizes the manufacturing similarities and differences between crystalline silicon bifacial and monofacial p-type wafers in a table reproduced below:

The second step in BSP formation involves the doping of silicon wafers with boron (BBr₃) done in a very precise manner. The third step is needed to prevent the recombining of energized electrons back into PV material before they form electrical current and move in an organized stream out of the solar cells and into your home.

Other types of bifacial solar cells are manufactured differently. The section below presents some key distinguishing features of these processes. 

What are the 5 types of bifacial solar panels?

There are five major types of bifacial solar panels (BSPs) on the market today. They differ in the type of solar cell used. 

Monofacial solar modules may also employ these cell types. A plus (+) sign after the cell’s acronym is sometimes used to denote a bifacial solar cell.

1. Passivated emitter and rear cell or contact (PERC) 
2. Passivated emitter rear totally diffused (PERT) 
3. Passivated emitter rear locally diffused (PERL)
4. Silicon heterojunction with multiple intrinsic thin layers (HIT)
5. Interdigitated Back Contact (IBC)

According to industry analysts, the most common type of BSP employed today is PERT. HIT is in second place followed by PERC+.

1. PERC solar cells

PERC solar cells currently dominate the PV industry, replacing the traditional aluminum back surface field solar cells (Al-BSF). 

The graph below summarizes the shift in cell types across the PV industry.

All PERC and PERC+ solar cells feature passivation and dielectric capping layers that conventional mono- and polycrystalline Al-BSF solar cells do not have. You can see them in the diagram below of a side view of a PERC solar module:

The passivation and dielectric capping layers consisting of various high-quality metal oxides prevent surface recombination of electron-hole pairs. This means instead of rejoining and merging back into the PV material of the cell, energized electrons separate and move in an organized fashion forming the electrical current that starts its journey into your home.

Here’s a schematic showing PERC and PERC+ side by side:

Fortunately, the manufacture of PERC+ in factories which already make PERC cells is possible. Practically no modification of the production line from PERC to PERC+ is needed. Just a change of the screen-printed grid layout is required.

2. PERL solar cells

PERL, as well as PERT, solar cells are improvements on PERC cell technology but very similar in design and manufacture. They have been shown in laboratory tests to achieve up to 25% efficiency. Incidentally, recycled silicon used in PERC cells can reach almost 20% efficiency.

In PERL, electron-hole recombination in the rear is reduced by diffused boron or phosphorus doping only at the metal contact points. This means freed electrons don’t easily return to the PV materials in the cell. 

Rather, they become part of the electric current that feeds the electrical devices and appliances in your home.

3. PERT solar cells

In PERT, boron or phosphorus diffusion occurs throughout the back surface.

PERT is a popular choice for bifacial solar cells because it undergoes very little light-induced degradation (LID) unlike PERC cells.

4. Heterojunction with multiple intrinsic thin layers (HIT)

Heterojunction (HJT) solar cells feature a layer of crystalline silicon (c-Si) sandwiched between two layers of amorphous silicon (a-Si). HIT cells have many more ultra-thin a-Si layers than HJT cells.

Here is a schematic of a HJT solar panel side view clearly showing the a-Si layers:

For comparison, here is a diagram of a HIT solar cell. TCO in the diagram stands for transparent conductive oxide. TCO could be any number of metal oxides that play an important role in electrical conduction.

HJT and HIT cells enjoy extremely low temperature coefficients (~0.26%/°C). They are highly efficient as well (24%+). Plus, they are easier to manufacture than conventional mono- and polycrystalline solar cells. The process is simpler and also less energy intensive. 

HIT cells are perfectly suited for bifacial applications because the rear cell efficiency approximates the front cell efficiency. In other words, the back cell can convert as much solar energy to electrical energy as the front cell under the right conditions!  

The ratio between the rear and front power outputs (sometimes efficiencies are used in the mathematical formulas) is known as the bifaciality factor. See below for more on this. 

For HIT cells, the bifaciality factor is 92-100% with optimization. In PERC+ cells, by contrast, the bifaciality factor may hover around 65-80%. This means the bottom solar cell produces only 65-80% of the power generated by the top solar cell.

What is the bifaciality factor? [A sample calculation using the bifaciality factor]

The bifaciality factor, B, is a metric used to quantify how well the back solar cells in a bifacial solar panel perform compared to the front solar cells. 

Mathematically, B is a ratio of the maximum power points (as displayed on the I-V curve) for both rear and front cells at standard test conditions. The bifaciality factor is often expressed as a percentage.

B = [P_{mpp, rear} /P_{mpp, front}]  x 100

Prospective buyers interested in using the bifaciality factor to calculate the maximum power output from the rear side of a bifacial solar panel may be able to do so using numbers from panel specification sheets. 

Each company presents their panels’ specs differently, and all the data you need may not be there. The bifaciality factor may not be given. When in doubt, call the company for more information.

As an example, Hanwha bifacial Q.ANTUM cells spec sheets list the bifaciality factor as 70% +/- 5% under standard test conditions (STC). So, using the P_mpp of the front panel given in the specs as 470W, the P_{mpp, rear} must be (when you rearrange the equation above):

 P_{mpp, rear} = B x P_{mpp, front} = 0.70 x 470 = 329W

However, the P_mpp for the entire bifacial solar panel — in the column called BSTC on the spec sheet — is 514W. It is not, as you may expect if the maximum powers were additive: 470W + 329W = 799W.

In the real world, the tilt angle of the solar array, height off the ground, altitude, and albedo largely determine how much power the bifacial solar module as a single functional unit will actually produce. 

Other factors, such as shading, soiling, and the many types of panel degradation, also influence the final number.

When sizing your solar system using bifacial solar panels, some companies, like Prism Solar, will indicate directly on the spec sheet that you should use the BSTC value of the maximum power point, not the value listed for the front side only to determine how many panels you need to meet your household energy demands.

5. Interdigitated Back Contact (IBC)

In IBC (rear contact) solar cells, the metal contacts (electrodes) through which electrical current passes are placed entirely on the back of the module. This placement eliminates energy losses due to shading on the front cell. 

The difference amounts to a 5-7% gain in electrical current, leaving IBC cells vs. cells with front-facing electrodes.

Through this arrangement of conducting wires in IBC solar cells, the front side has the fewest obstacles to light absorption. All electrical conduction and energy conversions occur on the module back. 

What is the preferred metal used in bifacial solar panels?

In PERC+/PERL/PERT bifacials, silver is still the most preferred metal to use. It is highly conductive. 

Although there has been a significant reduction in the amount of aluminum in PERC+ compared to PERC solar cells — from 1.0g to 0.2g per silicon wafer — this is not the case for silver. 

Researchers are working on finding cheaper silver substitutes for efficient electrical passage in solar cells, especially since the cost of silver has increased substantially in recent years. Silicon heterojunction cells in particular hold much promise in maintaining high efficiency with less expensive metals. 

Along with silver, the scarcity of other metals significantly contributes to the cost of solar panels. Monofacials of all cell types also use silver, so the problem of silver metal scarcity is PV industry-wide.  

How common are bifacial solar modules in the solar industry?

According to The International Technology Roadmap for Photovoltaic (ITRPV), in 2020, bifacial solar cells made up 20% of the solar cell market. Experts predict that by 2030, market share will increase to 70%. 

However, the actual and predicted market shares for bifacial solar panels (BSPs) are not as remarkable for the same time period. In 2020, a mere 12% of the solar panel market belonged to BSPs. The percentage is expected to climb to only 30% by 2030.

So the logical question about the apparent incongruence between these numbers is: What’s going to happen to all the bifacial solar cells that will be manufactured by 2030 if they won’t be in bifacial solar modules? 

Solar industry analysts predict that bifacial solar cells will become incorporated in monofacial modules constructed with special features. 

White back encapsulant or reflective back sheets in these modules will enhance the modules’ power ratings. In effect, modules constructed in this manner are like bifacial-monofacial hybrids.

It remains to be seen how these modules will be priced or what they will be called. Keep your eye on this space for updates on bifacial-monofacial solar panel hybrids.

Are bifacial solar panels more expensive than monofacial solar panels?

It is commonly believed that bifacial solar panels (BSPs) are significantly more expensive than their monofacial counterparts. This was true before PERC cells became mass produced in the mid-2010s, but it is no longer true today.

The National Renewable Energy Lab (NREL) released a price-per-watt cost comparison between monofacial and bifacial solar panels in 2019. Some types of BSPs have achieved price parity with monofacials — or are very close to it — as the graph below illustrates:

Are bifacial solar panels twice as efficient as monofacial solar panels?

In general, bifacial solar panels (BSPs) are not twice as efficient as monofacial solar panels in converting solar energy to electrical energy except possibly in lab settings using certain types of bifacial solar cells.

Today, PERC cells in monofacial solar modules afford an approximate 22.5% efficiency. This is the practical upper limit for mono PERC modules.

However, in a BSP PERC (noted as PERC+) module, overall efficiencies 11% greater than monofacial counterparts are possible according to studies by LONGi, a major solar manufacturer. 

For example, if that study is accurate, a bifacial solar panel with the same type and number of solar cells, tested under the same operating conditions and positioned in the same way as its monofacial counterpart that has a 20% efficiency, will have an efficiency of 20 + 11 = 31%. 

How much is the energy boost of a bifacial solar panel?

The “energy boost” of a bifacial solar panel (BSP) compared to its monofacial counterpart refers to the additional energy yield afforded by the bottom side of bifacial PV modules. It tells you how much more power output you can expect from BSPs compared to monofacial PV modules of the same power rating (ex., 370W) set up in an identical manner. 

A 1982 study by Cuevas, et al., found that the energy boost of a BSP compared to a monofacial module just like it under the same operating conditions was 50%. For that study, the research team used special light concentrating systems that most people wouldn’t have access to or couldn’t afford.

More recent research shows that with an expensive solar tracking system, 27% energy yield increases are possible.

On various bifacial panel spec sheets we reviewed for this article, the energy boost from BSPs varied between 20-35%. However, and not to throw shade (no pun intended) on your high hopes for BSPs, other research shows energy gains of 3-10% are more realistic. 

What determines the energy boost of bifacial solar panels?

Several factors determine exactly how much energy boost BSPs will deliver. Researchers working for the solar company Solar World AG have identified two factors as the most important:

1. The albedo of the surface under the modules
2. The height of the bottom panel in relation to that surface. 

The team developed a complex mathematical formula to determine the additional energy gain from bifacials. Here it is:

Key to formula:

a = 1.037

A = row pitch between the modules

E = 2.718

B = 8.691

H = distance between the lowest point on the module

frame and the roof or ground

c = 0.125

Using the formula, they generated the following data displayed graphically below:

The researchers concluded that the surface with the highest reflective capacity (albedo) located approximately 18 in. (0.5 meter) below the bottom of the lowest panel row yielded the greatest energy boost.

Other solar companies recommend heights of at least 1 meter (36 in.) The ideal height according to their research is 1.2-1.3m (47-51 in.)

Installing bifacial solar panels

If you’re considering bifacial solar panels for your home as the major source of energy to meet all of your family’s needs, it only makes economic sense if you have plenty of space for a ground mount system (to avoid row shading) in an area with a very high albedo at a high latitude.

Latitude and bifacial solar panels 

Here’s a graph of data showing why 60° or higher latitude is best for optimal energy yield gain in bifacials with or without solar tracking compared to monofacials:

Another source comes to the same conclusion: 60° or higher latitude is optimal for BSPs.

Albedo and bifacial solar panels

Albedo varies widely among surface types. Here’s a table that quantifies albedo under standard test conditions:

Ideally, for a small solar array serving one home, an albedo of at least 50% is needed to make BSPs cost-effective.

By contrast, an albedo of 25%, common with vegetation or soil, results in a relative energy gain (compared to monofacials) of only 10%.

Note that albedo changes throughout the day and with the seasons. Some surfaces may receive reduced albedo over time due to weathering or soiling. When crunching the numbers to determine power output and how long your economic payback period or energy payback period will be, it’s important to take a changing albedo into account.

Ground cover ratio and bifacial solar panels

A metric used to quantify the needed space between panel rows to avoid shading is called the ground cover ratio (GCR). This is the ratio between the area occupied by the panels and the total available area. Studies show that 40-50% is the optimal GCR for a ground mounted bifacial solar system.

Are bifacial solar panels for homes worth it?

For most homes, bifacial solar panels (BSPs) to meet all of your energy needs are not recommended. However, there are a few situations where BSPs would do well. 

People living in snowy regions at or above 60° latitude with lots of land — Alaskans, this means you! — could make bifacial solar panels work for them if the panels are:

1. Installed vertically — portrait style — to shed snow and expose more of the panels quickly or tilted correctly for your region

2. Spaced far enough apart to prevent shading of one row on another

3. Lowest panel is 18 in. minimum up to 51 in. from the ground

4. Facing the east and west to get two power peaks per day (sun rising and sun setting).

Similarly, people residing in high-latitude or subtropical deserts could benefit from BSPs.

Urbanites living in buildings with reflective roofs in sunny places could also take advantage of higher albedo. A California project mapping out potentials for “cool roofs” in a number of cities showed it was possible.

Vertically-mounted BSPs would enhance green roofs, too, in urban scenarios.

This is no joke: observe the temperature differences on white vs. black surfaces.

In all these uses of small-scale BSP, the modules are tilted or vertical. They are never mounted flush to a rooftop, even if the roof has a high albedo. On a roof, there is not enough space for reflection followed by absorption of radiant energy by the rear solar cells unless the entire array is elevated.

However, due to wind gales that could whip off the array and send it flying, it is not a good idea to mount the panels so far off of the roof.

If homeowners would like to use BSP on their property, but only as a supplement to a rooftop array of traditional monofacial panels, bifacials could produce some energy if they are horizontally positioned in:

• Carports
• Canopies
• Pergolas 
• Patios 
• Awnings
• Balconies
• Deck coverings

Can bifacial solar panel canopies perform well in cities?

There is growing evidence from real-life examples that bifacial solar panels (BSPs) on canopies in urban settings can perform well. Brooklyn, NY-based Urban Energy recently completed its first BSP canopy in New York City. The 46 kW system consists of 118 BSPs rated at 390W each placed atop a low-and-moderate-income multifamily building.

The company states the shading factor was minimal on the canopy compared to other rooftop solar systems in the city. Other advantages of the bifacial canopy vs. standard rooftop solar in a metropolitan location include:

• Maximizes solar power output in a confined space
• Adheres better to building codes (no obstruction or fire lane intrusion) 
• Integrates well with battery storage and heat pumps

Urban Energy plans expansion to other NYC sites in 2023 with more planned for Chicago and Washington, D.C. in 2024.

Advantages and disadvantages of bifacial solar panels

Here’s a summary table of the major advantages and disadvantages of bifacial solar panels for homeowners considering them for a residential solar system. Most of these points have been discussed in this article, but a few are seen here for the first time.

Key takeaways on bifacial solar panels

Bifacial solar panels (BSPs) have grown in popularity in recent years. Unlike monofacial solar panels which produce energy on just one side, both the front and back sides of BSPs convert solar energy into electricity.

Given today’s technology, BSPs can achieve — under ideal conditions — a 25-30% increase in power output compared to monofacial solar modules. Realistically speaking, 3-10% is more likely.

Some BSPs are slightly more expensive than their monofacial counterparts due to advanced technology and more specialized mounting hardware. However, costs are decreasing as BSPs become more common. Today, certain types are cost-competitive with monofacials. 

Although bifacials are used on industrial and utility scales today, homeowners have fewer options regarding small-scale bifacial solar systems if they wish to save money on energy bills and enjoy a short payback period.

BSPs are not recommended for residential rooftop solar. There isn’t enough space for light to reach the bottom solar cells. However, if you have land for a well-spaced ground mount solar setup, bifacial solar panels could work. High altitude and high albedo are necessary for good solar power generation.

If you’re not able to support any kind of solar system on your property, participating in community solar programs may be an alternative way to get involved in the renewable energy transition while receiving energy cost savings. 

Just like magic, you imagine electricity flying through the air like invisible sparks, wirelessly, powering up the smartphone in your pocket or the tablet on your desk, and keeping them always topped off.

Low battery warnings? Permanently a thing of the past.

Investors, wanting to seize on the money-making opportunity presented by the notion of wireless electricity, rallied behind so-called nanocrystal electricity companies that supposedly could pull this off.

Not so fast.

Although there is science to support it, nanocrystal electricity exists mostly in labs today. You’ll read about some of this exciting research, especially in photovoltaics (solar energy).

You will also learn about unsuccessful investor campaigns to sell stock in nanocrystal electricity. You will meet a company wrongly associated with nanocrystal electricity, and find out what they are doing instead. 

In fact, this company is one of several tech startups that is taking the core concepts behind nanocrystal electricity and wireless electricity and running with it. Using various scientific techniques, they’re developing a type of wireless technology known as wireless power transfer (WPT). The startups are actively working on scaling it up for widespread use.

Find out here what WPT means for you — now and in the future. 

What is nanocrystal electricity?

Nanocrystal electricity refers to tiny crystals generating electric currents via the piezoelectric effect. There are two ways this effect happens: direct and inverse.

Direct piezoelectric effect

Mechanical pressure on extremely small (nano) crystals creates an electric current, as the diagram below of the direct piezoelectric effect shows.

Microphones and pressure sensors function because of the direct piezoelectric effect.

Inverse piezoelectric effect

Similarly, the inverse piezoelectric effect occurs when voltage is applied to a piezoelectric crystal, expanding or shrinking it. Speakers in phones and buzzers as well as sonar operate because of the inverse piezoelectric effect.

Here is a diagram illustrating the inverse piezoelectric effect on a nanocrystal of lead zirconate titanate:

Unfortunately, nanocrystal electricity could never work on a grand scale to power a home or a country because the electric currents produced are just too small to power anything for any significant length of time.

Yet somehow, in the late 2010s, investors began promoting nanocrystal electricity as the next big thing in green technology.

At the time, the startup tech company, Energous, was cited in a few articles and financial newsletters as spearheading nanocrystal electricity, a “disruptive” technology with great money-making potential. However, a 2018 article published by Nanalyze titled Investing in Nanocrystal Electricity Stocks stated clearly:

“In looking through the latest 10-K from Energous, not one mention is made of “nanocrystal” anything. In fact, not once are the words “nano” or “crystal” used in the entire document. So whoever decided to start calling wireless charging “nanocrystal electricity” should be slapped. Henceforth, we will try to never use this term again, and instead talk about “wireless charging.”

To support this conclusion, we spoke with Cesar Johnston, the CEO of Energous, in an October 2022 video call. He confirmed that nanocrystal electricity was never a part of their game plan or mission as a wireless power company. Johnston stated unequivocally:

“Energous has nothing to do with nanocrystal electricity.”

When asked how the mistaken connection between Energous and nanocrystal electricity could have gotten started, Johnston, suggested that the longstanding goal among scientists to “harvest” electricity in a way that didn’t depend on fossil fuels was probably behind it. He pointed out that researchers have been exploring alternative strategies to generate electricity, like using solar energy or radio frequency waves, for over a century. 

Besides Energous, there are several startups innovating in the wireless technology space. They are all featured later in this article.

But first, brief looks at nanocrystal electricity on an experimental scale and on the history of wireless electricity will help piece together this puzzle about how we got from nanocrystal electricity to wireless power transfer (WPT) via wireless electricity.

Nanocrystal electricity in the lab

In the 2010s, while investors began hailing — without good reason — the unlimited potential of nanocrystal electricity stock to make money, there were scientific papers related to the topic being published. It’s possible that the person who coined the phrase nanocrystal electricity considered this work as a scientific justification for it. 

However, the scientific advances on nanocrystals happening in research labs had nothing to do with electricity to feed the grid, power homes, or even recharge devices wirelessly — as the investors claimed. 

Nanocrystal research, for instance, falls within the emerging field of nanoscience in medical applications such as drug delivery. Several research teams look specifically at the electrical characteristics of nanocrystals. Here are three of them:

1. Electrical characteristics of nanocrystal solids

Photovoltaics refers to the use of sunlight energy to create direct current (DC) electricity. It’s the science behind solar panels.

There is an ongoing effort in the scientific and engineering communities to identify chemically stable and non-toxic crystals that efficiently convert solar energy to electrical energy. This paper discusses the testing of semiconductor nanocrystal solids for their electrical properties. The goal is to identify highly absorptive materials for advanced solar cells with superior efficiency.

2. Nanocrystal light-emitting diodes based on type II nanoplatelets

This work investigates a new class of semiconductor nanocrystals called nanoplatelets used to make brighter light-emitting diodes (LEDs). You are probably familiar with LEDs as the small red, blue, white, or green lights that indicate the charging or on/off status of electronic gadgets.

Researchers believe these nanocrystals can be used in solar cells or lasers as well as in high-performing LEDs. 

3. Strongly emissive perovskite nanocrystal inks for high-voltage solar cells

Perovskite nanocrystals hold much promise in photovoltaics as a silicon alternative. They are less energy-intensive to produce than conventional solar cells and generally are made with more environmentally-friendly substances. 

As of yet, perovskites aren’t stable long enough to be commercially scalable in solar panels. This means they degrade quickly. Research looking at the characteristics of specific perovskites, including their electrical properties, aims to overcome this technical barrier to creating highly efficient solar panels. 

A 2022 study proposed an experimental method of accelerated aging of perovskites. The researchers were able to estimate the stability of their perovskite solar cells to be 5+ years at elevated temperatures and humidity. Efficiency remained high. This is an incredible improvement compared to other perovskites. 

The new technique is an important tool with which investigators can measure perovskite solar cell longevity. Expect more technological advances with perovskites in the near future.  

General conclusion from nanocrystal electricity research

Labs researching the electrical characteristics of nanocrystals exist in academia, industry, and government today. As suggested here, most of it is related to photovoltaics. It is distinctly not about nanocrystal electricity on a commercial scale envisioned as an alternative to fossil fuel power plants, electrical substations, and high-voltage wires and poles stretched over much of the world. 

The dream of nanocrystal electricity to power homes, offices, and factories belongs only to investors hoping to sell stock in nanocrystal electricity companies — although there weren’t any.

However, the concept of wireless electricity is not new. For this invention, we have Nikola Tesla to thank. 

Nikola Tesla and wireless electricity

Nikola Tesla had big plans for wireless electricity as a late 19th-century engineer, physicist, and futurist credited with the invention of alternating current (AC) electricity used worldwide in homes, offices, and factories. However, none of his plans involved nanocrystals.

For Tesla, inventing many modern conveniences we still enjoy today, such as remote controllers, x-rays, neon lamps, and radios, was a mere prelude to his dream.

Tesla hoped to electrify the world wirelessly. For him, wireless transmission meant “a great step will be made toward the unification and harmonious existence of the various races inhabiting the globe.” 

Tesla started the project in 1902 in New York but couldn’t complete it when his funding was cut by a wealthy banker who probably didn’t want electricity to be free as a public good. Yet his research was of such great significance for the potential it had to upend the energy production status quo that it was confiscated by the FBI after his death.

Earlier in 1893, at the Chicago World’s Fair, he had proven the concept of wireless electricity in an exhibition room. For this, he invented a type of wireless power transfer (WPT) called resonant inductive coupling. To the amazement of bystanders, he demonstrated that electricity could be transmitted and used wirelessly. 

With this invention, Tesla lit up lamps with no wires. He called it “cold light” created in glass tubes containing gases when close to an electric current moving through the air in the room. He wrote a 1901 newspaper article describing his experiments.

How does resonant inductive coupling work?

Tesla generated electricity wirelessly through resonant inductive coupling using another of his well-known inventions: the Tesla coil. This device is a special type of transformer consisting of two loosely coupled resonant circuits. It is capable of producing extremely high-voltage, high-frequency, but low-amperage alternating current (AC) electricity inside a strong magnetic field. 

In a Tesla coil, electrical charges can jump across an air (spark) gap as arcs. The maximum amount of electricity that can be transferred across an air gap occurs when the two circuits oscillate at the same frequencies. Tesla claimed that his wireless electricity could be transferred with only a 5% energy loss. 

How did Tesla plan to take wireless electricity around the world?

Tesla’s vision with resonant inductive coupling as a form of wireless power transfer was to apply it on a grand scale and take wireless electricity around the world. One of the ways he hypothesized it could occur was by tapping into the Earth’s resonance. 

Based on many of his experiments, Tesla came to view the Earth as a massive electrical power conductor that could be made into a generator. First, he observed that the Earth possessed a natural electric charge with its own specific vibrational frequency. 

Then he hypothesized that by matching the planet’s frequency with that of an electric oscillator, and stepping it up further with a magnifying transmitter — instruments which he also invented —  he could excite a low-frequency ground wave called the Zenneck surface wave. The Earth’s electric current would travel via these waves underground, producing wireless electricity anywhere in the world.

So it was feasible to Tesla that he could run AC electricity across the Atlantic Ocean not with wires but through the underground tunnels located around his lab and the Wardenclyffe Tower in New York. The Tower itself was 100 ft. in diameter and over 200 ft. high. 

Researchers speculate that “…the deep tunnels seem to have been constructed to increase earth coupling for grounding and/or to initiate standing waves for the projection of electricity to remote locations.”

According to Tesla’s view, by tapping into the electric current traveling underground through the Earth’s own natural resonance, you could access the electricity anywhere on Earth — without wires.

In Tesla’s own words: “When wireless is fully applied, the earth will be converted into a huge brain, capable of response in every one of its parts.”

Here is a copy of an original drawing from Tesla’s 1907 patent application for “an apparatus for transmitting electrical energy”:

As of today, no company has seriously picked up the torch lit by Tesla. Instead, the world relies on an antiquated electric grid, ironically also developed in part by Tesla. In the United States, except for 13% from wind and solar energy sources, fossil fuels (coal and gas) supply over 60% of the electric grid. This fossil fuel burning is fueling the climate crisis today.

Did Tesla complete his global wireless electricity experiment?

Because Tesla’s employer, the Westinghouse Electric & Manufacturing company, had so heavily invested in building the grid’s infrastructure in the United States — with Tesla’s ingenuity behind it, of course — they were unwilling to forego its money-making potential and take a risk on developing Tesla’s wireless electricity. 

At the time, the cause-and-effect relationship between fossil fuel burning and climate change was not well known, even though a few scientists had predicted and demonstrated the global warming potential of carbon dioxide.

Notable among them were the first researchers doing climate science: Eunice Newton Foote in 1856 and John Tyndall in 1859. 

In 1938, G.S. Callendar showed for the first time that it was “artificial” (human-caused) fossil fuel burning that was increasing carbon dioxide in the atmosphere as well as the global temperature.

What are the consequences of using the electric grid instead of Tesla’s wireless electricity?

At the turn of the 20th century, with Westinghouse’s Tesla in charge, human civilization was on track for burning up the stored carbon from millions of years of plant and animal decomposition in order to keep the grid working. Today, just 100 years or so later, humanity is beginning to experience the adverse climatic effects largely resulting from that choice. 

Known for high transmission losses — over 13% in some states as the diagram below shows — and prone to shutdowns during peak demand times, the electric grid is not the most efficient way to power a country. High-voltage wires strung on wooden poles are vulnerable to climate crisis-intensified storms.

Further, there is evidence that aging equipment is a prime cause of some wildfires in California.

Today, there are new problems for the grid. With the push toward renewable energy, electric vehicles, and electrification of all sectors, some researchers provide evidence that there is serious doubt whether the present grid can handle the heavy loads that are increasingly being put on it.

There is no question that the company that makes wireless electricity for the world — as Tesla envisioned — on a commercial scale will not only save the day (and the world) with clean, green power. This company will likely earn billions in profits.  

From nanocrystal electricity to wireless power transfer (WPT) 

The core concept of producing, transmitting, and consuming electricity without wires is at the heart of all wireless technology, including wireless power transfer (WPT). However, there are no nanocrystals involved in any of the technology arising from companies innovating in the WPT space today.

As explained earlier in this article, nanocrystal electricity was a hyped-up scam by investors meant to attract people looking to invest in “disruptive” green technology. WPT is somewhat like what the nanocrystal electricity scam envisioned: electricity traveling wirelessly to power devices across a distance.

However, don’t think WPT is brand new. It’s been around for at least a century, but just not marketed as WPT is today.

What is wireless technology and wireless power transfer (WPT)?

Have you ever heard of radio telemetry, satellite communications, or radio frequency identification tags (RFIDs)? They are examples of wireless technology.

Here’s a brief rundown on what these early forms of wireless technology do:

1. Radio telemetry 

Telemetry uses sensors to collect data (current, temperature, pressure, etc.) from a remote location. The information is converted to voltages, combined into a single stream, and transmitted. Upon reaching a receiver, the data are separated and analyzed.

The first time telemetry was used in the early 1900s; it moved data from power plants to a central office via telephone lines. So, it wasn’t truly wireless at the start. 

In the early 1960s, radio telemetry became widely used to track wildlife at a distance. Very high frequency (VHF) radio telemetry is currently the most commonly used practice for animal tracking. Besides a transmitter and receiver, an antenna is involved. Animals are given their own frequencies in the 30-300 MHz range allowing specific individuals to be tracked for long periods.

2. Satellite communications

Satellites and other spacecraft take photos and collect data on their current status and location. They communicate this information via radio frequency waves beamed down to large antennae on Earth. One antenna could be over 200 feet in diameter. The antennae make up the Deep Space Network (DSN) and are located around the world.

Similarly, space agencies send information to satellites via the DSN. An example is a list of instructions for a repair.

Here’s a photo of the Mars Antenna in California.

3. Radio frequency identification (RFID) 

Radio frequency identification (RFID) is a form of wireless power or communication based on radio frequency waves. It dates back to the 1940s. RFID can uniquely identify a person, animal, or object.

RFID systems consist of three components:

• Scanning antenna
• Transceiver
• Transponder 

The antenna and transceiver may be combined in a reader (either portable or stationary). The transponder is in the RFID tag.

Readers and tags “talk” to each other via radio waves. First, a reader sends out a signal to activate a tag. Then, the tag responds with a signal of its own. The signal is translated into data such as location. Tags may have their own power source (batteries). Or, tags could run off of the power supplied by a reader through electromagnetic induction of an electrical current in the tag.

Simple RFID tags are smart labels that feature a bar code. No specialized equipment is needed to print out an adhesive smart label and display it in a store.

Common applications of RFID technology include:

• Passports
• Pet tracking
• Inventory 
• Vehicle tracking
• Shipping
• Healthcare
• Some credit cards

Wireless Technology: Then and Now

Wireless technology has undergone significant development since its debut in the early 1900s. Begun as a way to transmit data without wires, it now also moves electrical power wirelessly. Thus, its name: wireless power transfer (WPT).

Initially, WPT transmitted only very small amounts of power in the microwatt to milliwatt range. By contrast, modern WPT moves a few watts up to several kilowatts over larger distances.

In recent years, WPT has exploded to include cell phone, tablet, and drone charging, stationary charging of electric vehicles (EVs), and dynamic charging of EVs known as road-powered EVs (RPEVs).

For EV applications, industry has created a special branch of WPT, called inductive power transfer (IPT).

The diagram below gives an overview of the many types of WPT in existence today. The schematic indicates the way power passes over the air gap between the transmitter and receiver.

What is Qi charging?

In 2008, the Wireless Power Consortium (WPC) developed standards for wireless battery charging, also called Qi (“chee”) charging. The standards apply to both inductive and resonant WPT technologies.

Here is the Qi logo on a charging pad:

Inductive charging often involves use of a charging pad. Resonant charging may not need a charging pad.

Qi charging up to 15 watts is possible today. Note that not all devices on the market today have met Qi standards. Look for the Qi logo to be sure.

As of this writing, 9,113 gadgets are qualified by the WPC. This means they have undergone testing and completed the certification process. The fields they create will not harm sensitive equipment such as implanted medical devices. Qi-registered products can be safely charged with Qi-certified chargers. Visit the Qi database to see if your device is certified.

Are the electromagnetic fields produced by wireless charging harmful to human health?

Wireless charging produces an electromagnetic field (EMF). Most experts (but not all) do not consider it to be harmful to human health because the levels are so low.

However, if you have very sensitive equipment, such as some implanted medical devices, it could cause a disturbance.

When EMFs become more powerful and ever-present with advanced WPT technology, wireless charging could present more of a health hazard. Currently, EMF radiation is highest very close to charging pads. There is none when there is no device on the charger being charged.

If you’d like to measure the EMF generated by your wireless charger, this portable gizmo, a Trifield TF2, will deliver all the data you need to make your assessment.

WPT company profiles

Here’s a brief look at what’s going on and what’s up and coming in the wireless power transfer (WPT) world in 2022.

Energous

Energous  are developers of WattUp, a government-approved and -regulated technology for desktop, near field, and far field charging, Energous is a leader in the WPT space. The company uses radio frequency (RF) waves to power devices wirelessly. 

Energous wireless products work through a transmitter and receiver. The transmitter sends energy via radio waves to a WattUp-enabled receiver in a chargeable device. The receiver converts the radio waves into DC electrical power that charges the device’s battery.

As of today, the maximum distance between transmitter and receiver allowable for Energous’ power transfer of up to 15 watts is 15 meters. Placing transmitters in a long string — always 15 meters apart — will permit unlimited wireless transfer. 

The WattUp technology uses radio frequencies that are different from those used by WiFi or Bluetooth, so interference is not a problem. 

Currently, Energous is focusing on batteryless tags and radio frequency identification (RFID) tags for various commercial applications. This work will eliminate the need for batteries. 

One of Energous’ latest projects is developing a low-power carbon dioxide sensor. This technology can be used in monitors for indoor air quality.

According to the Energous website, the company holds over 200 patents. It is approved to ship its products in 112 countries including the European Union and North American markets.

Powercast

Powercast WPT is based on radio wave (RF) energy to power devices via transmitters and embedded receivers. Once the receiver transforms RF energy to DC electrical current, the energy could be used to power a batteryless device or to recharge a battery already in the gadget.

Some of the applications of PowerCast products include:

• RFID (radio frequency identification) used for environmental monitoring
• Battery recharging for wearables and other consumer devices
• Batteryless price tags 
• Smart cards
• LED-based packaging.  

Powercast’s wireless technology automatically turns on when it senses that nearby devices need charging. Similarly, it deactivates when they’re fully charged. Alternatively, Powercast’s products can be set to deliver power continuously, or on a scheduled basis.

WiTricity

Electric vehicle (EV) charging by WiTricity is painless without cables or cords using highly resonant WPT.

Invented by Massachusetts Institute of Technology professor Marin Soljačić in 2005, this type of WPT couples the magnetic fields of two specialized devices with closely matched resonant frequencies into a single continuous magnetic field. This coupling enables the transfer of electrical power from one device to the other at high efficiency and over a long range.

With this WPT technology, charging an EV is as easy as driving up to a designated spot (like your garage) and recharging automatically. No need to plug in your vehicle, or even get out of the car. But if you’re worried about EMF radiation, you’d want to get out.

The WiTricity system is composed of three parts:

• Wall box that converts a power source, such as the electric grid, to high-frequency energy delivered to the charging pad.
• Charging pad contains the coil and associated parts that transforms the high-frequency energy into a magnetic field that enters a receiver in the EV
• Vehicle receiver captures the energy from the magnetic field and converts it into the DC electrical current that recharges the battery. 

WiTricity WPT will operate efficiently to charge all types of EVs.

Ossia

Started in 2008 as Omnilectric, Ossia is a wireless tech company using radio frequency waves to power devices at a distance. 

Through its flagship product called Cota, radio frequency waves carrying power travel from transmitters to receivers embedded in a wide range of electronic devices. Cota charges them wirelessly.

So far, Cota technology is used in consumer electronics, medical devices, industrial equipment, and automotive applications. There is no charging pad or wires used.

Without being tethered to a charging pad, users can walk around holding their device while it’s being charged. Cota technology is built to allow the receiver’s beacon signal to use walls and objects, but never pets or people, to find a path to a transmitter. 

Ossia holds over 180 patents, and its products are approved for sale in over 45 countries.

Final thoughts on wireless technology, wireless electricity, and nanocrystal electricity

Nanocrystal electricity was the enticing tech stock buzzword that investors didn’t flock to, suspicious of it being a scam. Investors touted it as the way to revolutionize human civilization by making electricity flow via tiny nanocrystals instead of wires. The investors attempted to attract big money to so-called nanocrystal electricity companies supposedly developing this technology.

Nothing materialized from the investors’ efforts in nanocrystal electricity. There is some work in research labs on using nanocrystals to create electricity, mostly in photovoltaics.

The invention of wireless electricity belongs to Nikola Tesla at the beginning of the 20th century. Although he didn’t fully realize its potential, several companies are working today on developing a type of wireless technology called wireless power transfer (WPT). 

Employing principles of radio frequency (RF) waves, ultrasound, lasers, or magnetic resonance, these companies are transforming how electricity is transmitted and consumed. 

For example, it’s now possible to recharge small electronic devices and electric vehicles wirelessly. There’s no need for a separate charger, bulky plug, or electrical outlet.

With each new development in wireless technology, it may soon be widely available to everyone to recharge gadgets and electric cars without charging pads. Maybe one day wireless technology will power your home and office, too.

Many other states hold the same — or similar — view.

This is just one example of how the public perception of hydropower as a great technological achievement of cheap, renewable energy is rosier than reality.

In other ways as well, as our climate crisis dries up the Earth in many places, any advantages of hydroelectric power are quickly becoming liabilities.

In this article, you’ll find out exactly how the apparent pros of hydroelectric power could actually be viewed as cons — with one exception.

There’s only one real pro of hydroelectric power: energy efficiency 

When hydropower is used on a microscale, it can be an inexpensive source of renewable energy with little to no environmental damage. This is one clear pro of hydroelectric power; it is a relatively efficient source of electricity.

The qualifier relatively is needed because efficiency is dismal when you’re talking about electricity generation.

The U.S. Energy Information Administration states that 60% of all energy used to create electricity is lost during its production.

Let that sink in for a minute, especially in light of the current global energy crisis.

So how exactly is hydroelectric power energy efficient?

What is energy efficiency?

There are a couple of different ways the term energy efficient is used. 

According to the Environmental and Energy Study Institute, energy efficiency is a term that refers to using less energy to perform a task (not wasting it). 

Think of EnergyStar rated appliances as being more energy efficient than others that haven’t earned that status.

Another way to describe energy efficiency is by how much usable energy a source produces (output) from what it has to start with (input). It’s often given as a percentage. 

In the case of electricity, the percentage is a ratio between the energy that a source generates (electricity output) and the sum of all the energy inputs required to create it, multiplied by 100. 

When it comes to making electricity, there are a number of inputs to factor into the levelized cost of electricity (LCOE). These are costs of:

• Capital 
• Fuel 
• Operation
• Environmental damage 
• Down times at the energy plant

After considering all of these elements, here is a graph of the efficiencies of the most common energy sources:

You see that hydroelectric energy far surpasses all types of nonrenewable sources of energy (fossil fuels) in efficiency. 

Hydropower also outdoes the energy efficiency of solar (317% vs. 207%).

Notice from the graph that wind knocks energy efficiency out of the park (1,164%)! Geothermal is better than hydro at 514%.

Notably, unlike hydroelectric power, solar and wind efficiencies are growing rapidly due to active R&D, especially in recent decades.

However, although this pro of hydroelectric power is relatively strong, its value is diminished by all of the major cons of hydroelectric power.

So what’s wrong with hydroelectric power?

Here are six major cons of hydroelectric power. Depending on the source, you may find some of these cons of hydropower are actually presented more like positives but if we are being critical, the conclusions drawn can be vastly different.

1. Hydroelectric power is no longer renewable

Many states actually do not count large-scale hydroelectric power as renewable energy, but they do include small-scale hydroelectric power on their renewable energy balance sheets.

What they consider large or small varies from state to state, but 25-30 MW is usually the dividing line between them.

What are Renewable Portfolio Standards (RPS)?

The renewable energy numbers game that states play is related to their renewable portfolio standards (RPS). This is their method to demonstrate how they are achieving their state-mandated carbon emissions goals. 

States require in their RPS by specified percentage exactly how much electricity sold by utilities comes from renewable resources.  

It’s policies like RPS that drive growth in renewable energy production in the U.S. In fact, since the early 2000s, approximately half of renewables growth is due to RPS, according to the National Conference of State Legislatures.

More recently, some states have introduced Clean Energy Standards (CES). The difference between RPS and CES depends on how a state defines a renewable vs. a clean source of energy. In most cases, clean refers to carbon-free energy sources.

The map below shows you how the states stack up on RPS.

Here are how the states with ambitious climate goals compare on RPS/CES:

However, our point about hydroelectric power as no longer renewable is not simply to be in agreement with many states.

It is much larger than this.

Effect of our climate crisis on hydroelectric power

The August 18th, 2022 front page of the New York Times sums up the effect of our climate crisis on hydropower nicely: 

“Heat and drought have reduced hydropower in Norway, threatened nuclear reactors in France and crimped coal transport in Germany.”

And that’s just Europe. In only two months.

Here’s how Europe’s energy crisis is devolving on the infographic below. See how hydroelectric is down. Nuclear is down due to the increased temperature of water making it impossible to cool down radioactive rods.

Note the double-digit growth in solar and wind. Unfortunately, coal is picking back up due to Russian president Putin shutting off gas to some regions. The small rise in gas is due to increased gas imports from the U.S.

As widespread, prolonged drought — termed aridification — occurs the world over, humans must acknowledge then rapidly adapt to the fact that if carbon emissions are not drastically reduced this decade, freshwater will become increasingly difficult to find.

Water is the new gold.

For example, as the deadline passes for stakeholder states dependent on the Colorado River for life and livelihoods to draw up a plan for water conservation and equitable allocation as river levels plummet due to our climate crisis, the federal government will step in and do it for them to avert catastrophic collapse.

This could lead to armed conflict among thousands — if not millions — of people as water scarcity intensifies.

So, when mega-drought conditions are slowly expanding across the nation, maybe it’s not a good idea to include hydroelectric power in the reliable energy supply mix? All other forms of energy production (except biomass) use a lot less water as the diagram below shows.

(Note: PV = photovoltaic or solar; L= liter; MWh = megawatt hour. 1 MWh = 1 million watt hours.)

Effect of our climate crisis on hydroelectric power in California

The Colorado River feeds the two largest reservoirs (when filled to capacity) in the U.S.: Lakes Mead and Powell.

Here’s a short video on the amazing Colorado River:

Lake Mead is the water source for more than 25 million people and supplies agricultural land across three states. Currently, the mega-drought has pushed it to its lowest level ever. 

The extreme drought in the U.S. West is so bad that you can see its effect on the Colorado River and the major hydroelectric dams it feeds from space.

In California, hydroelectric power plants are shutting down — sometimes for the first time in history — as reservoir levels drop to their lowest levels ever. Climate crisis-intensified heatwaves driving encroaching aridification (low snowpack levels and less rain are the cause).

The state imported 30% of its energy in 2020 but is still struggling to make up for hydropower shutdowns resulting in 3.5 GW power shortfalls. So, power outages become commonplace, if not because of hydropower deficits, then for outages to protect grid infrastructure during wildfire season. (1 GW = 1 billion watts.)

The future of hydroelectric power in a climate crisis

Hydroelectric power water deficiencies due to our climate crisis severely restricting the availability of freshwater are not just in the USA and Europe as discussed in the preceding sections. 

Heavily industrial parts of China are feeling the heat, too, in the longest heatwave in world history (70+ days) now in Summer 2022. Some municipalities are shutting down factories for days at a time to protect the grid. 

Consequently, China’s economy has already contracted this year. Only 2.8% growth is expected this year (down from the country’s projected 5.5%). 

Since much of the world’s goods originate in China, a cascade effect resulting in supply chain disruptions leading to further economic downturns is predicted globally.

Furthermore, many aging dams are literally falling apart, unable to withstand extreme weather. For example, under the onslaught of torrential rains — also an effect of our climate crisis — they could collapse, triggering massive evacuations or mortalities.

Perceptive readers see where this is going.

It is unwise — in fact, foolish — for governments to count on freshwater as being readily available any more for hydroelectric power. Especially when there are renewable energy sources with steady, assured inputs: solar, wind, and geothermal energies.

In fact, a 2022 study clearly forewarns that because of global heating leading to increased aridification, the future of hydroelectric power in the U.S. and elsewhere looks grim.

Here are just a few of the astounding predictions from that study:

•  61% of all global hydroelectric dams will be located in water basins with very high or extreme risk for droughts, floods or both by 2050. 
• By or before 2050, 20% of existing hydroelectric dams will be in areas of high flood risk. (Today, it’s a 4% risk.) 
• Currently, 2% of planned dams are in water basins with high flood risk. By 2050, that risk increases to 40%.
• 80% of all planned dams are in areas with high risk to further biodiversity loss. (Since 1970, freshwater fish populations have declined by 84%, and hydroelectric dams are considered the major cause.)  

What is not emphasized enough is that the planet is in a record La Niña, or “cool phase,” of the El Niño Southern Oscillation (ENSO).

Can you imagine what the temperature — and the drought level — will be when the hotter El Niño returns in 2023?

On a somewhat optimistic note, however, seawater is readily available as a tidal hydroelectric power source. Hopefully, marine hydrokinetic energy research and development will scale up soon on a grand scale to complement solar, wind, and geothermal energies.

2. Hydroelectric power is environmentally destructive

There are several aspects of hydroelectric power that are environmentally destructive. They fundamentally alter river ecosystems and the surrounding wildlife habitat.

Fish ladders

Readers may smile at the notion of fish ladders on some — but not all — conventional hydroelectric projects and believe that hydroelectric power is eco-friendly.

As a series of ascending pools (steps), fish ladders, or similar elevators, flumes, or bypass channels to get around turbines, are the most commonly used methods to help the fish move through dams.

Other ways to accomplish this feat include barges, tankers, trucks, or even an airplane!

Dams with no fish passage modification in the Columbia River Basin block more than 40% of the native habitat once freely accessible to salmon and steelhead trout before dam construction.

Here is a schematic that shows one of the methods to allow fish to get by a dam.

Installing fish ladders was a part of most hydroelectric dam projects since the 1890s. In fact, the Federal Power Act of 1920, the Fish and Wildlife Coordination Act of 1934, and the Northwest Power Act of 1980 are examples of just three laws requiring fish passages at all hydroelectric dams on public lands.

Unfortunately, not all dam builders or local governments took the laws seriously. 

Only with the insistence of fish advocates to at least save some native salmon and other fish species was fish ladder technology and design taken seriously and equipment installed. Survival rates slowly increased.

Most of the time. At least for adult fish.

Sadly, in some cases such as in a study from the Northeast U.S., only 3% of fish make it home to their spawning ground even with a ladder present beside the dam. 

Assisting juvenile fish around the dams was a different story.

Results from the Pacific Northwest are mixed for juveniles. Some years have a survival rate of <3%, while others can be as high as 60%. Overall, success in terms of higher survival rates increased in the 1990s and later compared to those of the 1960s, likely due to advanced methods and more diligence.

Below is a diagram of one passage setup to assist juvenile fish around hydroelectric dams.

Tragically, it’s not just the fish ladders that are literal stumbling blocks for fish trying to swim up river or head out to sea.

Warmer water temperatures and lower river levels due to our climate crisis are perfect conditions to allow a fish parasite to thrive in Idaho to California rivers. As a result, massive fish kills in the hundreds of thousands of several species — including endangered Chinook salmon — become common.

Reservoir construction

In addition, the construction of reservoirs has led to massive destruction of habitat, including that of many endangered species.

A large hydroelectric power plant built on level terrain may inundate thousands of square miles, wiping out forests, wildlife habitat, and farms.

Entire human villages and towns are relocated in many cases as well. This uproots identity-forming cultural attachments to the land.

As the world faces the 6th mass extinction of species, wild nature is further encroached upon to make way for roads, cattle ranching, soy and corn crops for animal feed, palm oil plantations, and new housing developments. More destruction to make way for additional hydroelectric power plants doesn’t make biological or economic sense.

Without biodiversity, human civilization is at risk of collapse, too.

Here are some stunning statistics on how dams have led to massive biodiversity losses in the U.S. according to the group American Rivers:

• Seven dams on the Coosa River in Alabama led to more than thirty freshwater species going extinct.
• East Coast populations of Atlantic salmon have been decimated by dams blocking access to spawning 
• 29% of West Coast salmon populations are now gone. One-third of the remaining salmon populations are threatened or endangered.

Environmental concerns with reservoir water

The water in reservoirs is stagnant. There are several problems with this.

Algal blooms in reservoirs

Nutrient buildup in reservoirs leads to algal blooms, sometimes toxic ones, aggravated by climate crisis-induced warming. Since the algae are consuming much of the oxygen, little remains for fish, leading to higher fish mortality.

Methane production in reservoirs

Underwater plants, meanwhile, also suffer from lack of oxygen consumed by algae. As the plants die and rot, they release methane, a potent greenhouse gas that contributes significantly more to global heating than carbon dioxide.   

Recent research concludes that previous estimations on exactly how much methane is released from dam reservoir surfaces are too low. Current studies show reservoir surfaces release 25% more methane than previously thought.

In other words, more hydroelectric dams will accelerate our climate crisis. This fact is more evidence to support the conclusion that hydroelectric power is not clean energy.

Higher evaporation rate in reservoirs

Thirdly, unmoving water evaporates more quickly than moving river water. Thus, in a prolonged drought during heatwaves, reservoir levels plummet. Shutdowns of energy production result when levels get too low as described below.

Sedimentation in reservoirs

According to the U.S. Bureau of Reclamation, the buildup of sediments in reservoirs from agricultural runoff and heavy rains is a major problem. Up to 35% of the total water holding capacity of all U.S. dams has been reduced over time due to sediment loading alone (not counting effects of global heating that causes rapid water loss through evaporation). 

As dams age, sedimentation worsens and reduces the normal lifespan of functional dams, presenting multiple problems including:

• Decrease in reservoir storage capacity 
• Plugging up dam outlets and reservoir water intakes 
• Lowering water quality, negatively impacting both aquatic life and human recreation 
• Decrease in nutrient flows downstream, even as far away as coastal ecosystems 
• Increase in degradation of downstream habitats

The last point may seem counter-intuitive. Wouldn’t sediment-free water help downstream habitats?

“Hungry water” in hydroelectric power

Researchers describe the water that has left its sediment behind in reservoirs as “hungry water.” It is likely to accelerate erosion in the downstream river’s channels, banks, and beaches while it’s picking up sediment to replace what it lost back in the reservoir. In the process, this hungry water erases critical habitat features along and under the downstream water channels. These features, such as wetlands, pools, and runs, are needed for wildlife.

Viral spillover

Additionally, as wild animals’ habitat is severely reduced by human encroachment, the likelihood of viral spillover events from wild animals to humans increases. The chance of this happening also increases with climate change.

While humanity is still dealing with SARS-CoV-2, the virus that causes Covid-19, it certainly doesn’t need more pandemics.

River scarcity

For 100 years, the U.S. has built more dams than any other country. So it’s logical to ask: Is there any space left on rivers for more dams?

Unbelievably, thousands of new hydroelectric dams are planned or under construction worldwide, even in protected areas, and some on free-flowing, wild rivers. This construction would affect approximately 200,000 miles of river, surrounding ecosystems, and human settlements. 

If completed, the 2010 installed energy capacity from hydroelectric power (1,000 GW) would double in the next few decades by new hydropower plants.

That’s a big “if” because today, on a global scale, most investment is in solar and wind — not hydropower. In fact, the corporation that built the world’s large hydropower plant, the Three Gorges Dam in China, invests heavily in wind and solar.

That corporation is probably very relieved today it did so.

Low water levels in the Yangtze River are forcing widespread closures in the region due to megadrought and prolonged heatwaves as this video shows.

In the U.S., because of the dam collapses in California and Michigan in recent years, there’s no frenzy to build more dams like there was in the early 1900s. A drying climate is cementing that attitude.

However, there is still a lot of interest in the U.S. in converting smaller, non-powered existing dams to small-scale hydropower plants.

Several recent studies in China, Norway, and Spain have shown that small-scale hydroelectric power (<30 MW) is not cost-effective and comes at huge social and environmental costs. It takes significant amounts of money to fortify and equip non-powered dams so that they could generate just a relative trickle of electricity. 

Natural resources are limited, even more so in a climate emergency. Humans must use them wisely if civilization is to make it to 2050. More hydroelectric power plants of any size can’t be justified.

3. Hydroelectric power is not sustainable

The material used to construct hydroelectric power plants is primarily cement, one of the most unsustainable materials on the planet, that when set, becomes concrete.

Interestingly, cement is the most widely used material on Earth, after water.

To give you some idea of how much concrete (in cubic yards) is in a hydropower dam and associated structures, here are two examples:

• Hoover Dam in Nevada: 4.36 million 
• Grand Coulee Dam in Washington: 12 million

The concrete in the Hoover Dam, according to the U.S. Bureau of Reclamation (BR),

“…would build a monument 100 feet square and 2-1/2 miles high; would rise higher than the 1,250-foot-tall Empire State Building if placed on an ordinary city block; or would pave a standard highway 16 feet wide, from San Francisco to New York City.”

Similarly, the concrete in the Grand Coulee Dam, according to the BR,

“…could build a sidewalk four feet wide and four inches thick and wrap it twice around the equator (50,000 miles). You could build a highway from Seattle, Washington to Miami, Florida.”

Concrete is unsustainable for two reasons. First, the extremely high heat needed to manufacture it requires energy from burning fossil fuels, which produces greenhouse gases and contributes to our climate crisis. Cement also releases carbon dioxide in a chemical reaction while being mixed with other materials during manufacture. 

If cement were a country, it would be the 8th largest carbon emitter in the world.

Here’s a diagram to show you just how bad the concrete industry is in terms of carbon emissions:

Furthermore, most concrete is not recycled although in theory it can be. A study in California showed only 2-8% of concrete was recycled. The rest is landfilled after demolition.

The good news is that Solidia is making significant strides in greening cement. Carbicrete in Canada makes carbon-negative concrete. But there is still a long way to go to get the entire cement industry on board.

4. Electricity from hydroelectric power is not the cheapest available

Hydroelectric power advocates boast that it’s the cheapest electricity source known today.

Solar and onshore wind captured that spot in 2022.

Here is the breakdown measured in dollars per kilowatt hour ($/kWh) for the most common sources of electricity:

As noted above, in a climate crisis that is already leading to economic downturns on both national and personal levels, humans must spend limited resources, including money, wisely. 

This is more reason to choose solar, wind or geothermal to meet your household energy needs.

5. Hydroelectric power is not cost-effective to produce

Even though it is commonly believed that operating costs are minimal for hydroelectric power, comprehensive research in 2014 showed this was not the case. 

Of 245 large dams reviewed in that study, all built between 1934 and 2007, they were too expensive to yield a positive return — without even taking into account environmental costs. In fact, the average costs were 96% higher than the estimated costs^⁠. Additionally, on average, they took 44% longer to build than anticipated, decreasing the return on investment.

So, in drought-ridden areas, it may be permissible to allow hydroelectric power plants to function as long as possible under their current license, but then let the licenses expire.

Certainly, no new hydroelectric projects should be initiated anywhere, including renovating small non-power dams for hydroelectric power as explained above. Doing so is not economically viable.

Instead, focusing on tidal energy development — where no dams are required — looks promising since it relies on unlimited seawater.

Of course, renewable solar, wind, and geothermal energies must center predominantly in the future energy portfolio of humanity.

6. Aging hydroelectric dams are a big risk in intense floods

Just as our climate crisis is responsible for supercharging extreme drought worldwide, it is also the reason for intense flash flooding. When aging or poorly constructed dams are in the flood zone, disasters aren’t too far behind.

Dangerously, the world is entering a period of “mass aging” of dams. Tens of thousands of dams are 50 years old. Many others are approaching 100 years. 

In the U.S., by 2030, 70% of dams will be over 50 years old. In 2019, the U.S. Army Corps of Engineers estimated there are approximately 15,600 dams classified as “high-hazard Structures.” Thus, it’s no surprise the American Corps of Civil Engineers gave the U.S. a “D” grade on its dams in the Group’s 2017 Report Card.

There are some dam removal projects going on in many countries, including the U.S., but these are costly and many take years to complete. So far, the nonprofit group American Rivers estimates only 1,956 dams (<2%) have been removed so far in the U.S. 

The Biden Administration recently signed into law the Infrastructure Investment and Jobs Act. It includes $2.4 billion for the removal or retrofit of dams. This is a start, but it’s not enough.

Meanwhile, flash flooding is intensifying everywhere. 

In 2017, the tallest dam in the U.S., Oroville Dam in California, partially failed. Heavy rains damaged the main and emergency spillways, forcing the evacuation of 188,000 people in three counties. Repairs cost over $1.1 billion. Operations were shut down for three weeks.

As a second example, in 2021, two hydroelectric dams collapsed in Michigan, forcing the evacuation of 10,000 people and causing millions of dollars in property damage.

Like most dams in the U.S., they were non-federally owned. Since the owners declared bankruptcy, it’s unlikely flood victims will win in court for damages.

So, building new hydroelectric dams in the 21st century climate crisis is clearly a high-risk investment. Fortunately, significantly less risky solar, wind, and geothermal energies exist to power our homes and businesses.

Bottom line: hydropower may not be the clean energy source we need for the future

The only pro of hydroelectric power is that it is a relatively efficient form of energy.

It’s common to read on the internet that the major pros of hydroelectric power are that it’s:

1. Renewable energy
2. A reliable energy source
3. Very energy efficient
4. Cheap source of electricity
5. Cost-effective to build and operate
6. Able to meet peak electrical demand.

Sadly, none of these statements is true about hydroelectric power, especially in our climate emergency.

Global heating is drying up the Earth with mega-droughts all over. Scientists predict that unless carbon emissions are drastically reduced by 2030, there will be intensifying aridification (drying) on a global scale. 

Since the water cycle is no longer natural — also because of our climate crisis — water should not be viewed as a renewable resource like it once was. Water has become different from solar, wind, and geothermal energy — all of which are truly renewable. 

So, without enough — or any — water, hydroelectric power plants won’t generate electricity, let alone meet high demand.

It’s also true that major cons of hydroelectric power have become worse over time:

1. Adverse environmental impact
2. Risky aging dams

With increasing deforestation and massive loss of biodiversity worldwide, building more dams and reservoirs will restrict wild nature even more. Doing so will bring wild animals in closer, more frequent contact with humans, making spillover events of viruses infecting humans more likely.

Today, most rivers that meet the requirements for massive hydropower have already been dammed. If there were to be more upstream diversions of freshwater — already a precious resource — to build more power plants, communities and wildlife downstream would receive even less water, if any. 

Regardless of where opinion falls when it comes to determining just how ‘green’ hydropower is, it’s important to be clear on what, exactly, hydroelectric energy entails, to better understand its wider impact on the environment.

What is hydroelectric power?

Hydroelectric power refers to using the kinetic energy of moving water or the potential energy of unmoving water to generate electricity.

In most types of hydropower generation, the process occurs in five steps:

1. A water flow turns a turbine connected to a generator in a powerhouse.
2. The generator’s rotational energy is converted to electricity.
3. Electricity flows from the generator to a utility substation (transmission yard) where its voltage is increased.
4. Then electricity travels long distances via transmission lines to the power grid.
5. Electricity is delivered to businesses and consumers like you.

History of hydroelectric power

As described in the U.S. Federal Energy Regulatory Commission (FERC) document titled Hydropower Primer, water has been used for thousands of years in many parts of the world to create mechanical power to grind grain.

Over 200 years ago in the United States, the first dams were constructed to generate mechanical power at grain and paper mills as well as other industries.

The world’s first hydroelectric power plant was built in 1882 on the Fox River in Appleton, WI.

In the early to mid-1900s, as funded under FDR’s New Deal, many dams used for mechanical power were converted to hydroelectric plants. Additionally, hundreds of new plants were built just as the national electric grid was being developed.

The 1940s saw the biggest contribution of hydroelectric power to electricity generation in the U.S.: 40%.

Below is a map of where the federally-owned hydroelectric projects are located along with the hydropower plants owned by private companies, municipalities, electric co-ops, or private citizens. (The majority of all hydropower plants in the U.S. are non-federal.)

Current state of hydroelectric power in the United States

In 2021, according to the U.S. Energy Information Administration (EIA), only 6.5% of all utility-scale electricity produced in the U.S. came from conventional hydropower, defined as hydroelectricity generated from “natural streamflow.” 

With the exception of Mississippi and Delaware, all U.S. states have some form of conventional hydroelectric power:

To find out the latest reservoir storage levels and historical comparisons for many U.S. hydropower plants, you can use this interactive tool. If you’re one of millions of people who rely on the shrinking Colorado River for potable water or electricity, this tool is very informative.

At the very least, it could prepare you for upcoming water rationing or water bans in your area.

The future of hydroelectric power in the United States

According to the American Society of Civil Engineers, there are approximately 91,000 dams in the U.S. Only 3% actually produce electricity today. The majority of dams were built for commercial navigation, irrigation, water storage, or flood control.

After extensive review and analysis, experts estimate that suitable non-powered dams could generate only 4,800 MW of additional hydroelectric capacity after renovations and repairs. (1 MW = 1,000 kilowatts.) This is the equivalent of only 0.0048 terawatts or a mere 0.00012% of all the electricity used in the U.S. in 2021.

So the question of whether it makes economic sense to invest in hydroelectric power development by converting non-powered dams, especially when solar, wind, and geothermal energies are available as electricity sources, is very pertinent.

How does hydroelectric power work?

Have you ever seen a historic grist mill on the back roads of America, like the one in the photo below? 

That water wheel works on the same principle as today’s hydroelectric plants.

FERC’s Hydropower Primer provides a clear and concise description of how hydroelectric power works. Here is a brief summary.

Turbines in hydroelectric power

Since the early 1820s, three major types of “water wheels” have been invented. They were dubbed  “turbines” from the Latin word turbo meaning whirlwind or whirl by Benoît Fourneyron who invented the earliest type.

There are the three main types of turbines used in hydroelectric projects today:

1. Pelton
2. Francis
3. Kaplan

Here are schematic drawings detailing their differences:

To understand the different ways each turbine type operates, it’s helpful to know the basic principles of how water flows in hydropower setups.

Hydraulic head

In order to have hydropower at all, there must be a difference in elevation through which water falls. 

As it’s moving downward, the water possesses kinetic energy.

But even when the water is perfectly still in an upper reservoir behind a dam, it possesses that same energy in a different form called potential energy.   

The vertical change in elevation between the reservoir water level (head) and the downstream water (tailwater) is known as the hydraulic head. 

As you can probably guess, the world’s largest hydroelectric plants (30+ MW) have huge hydraulic heads of hundreds of feet. 

By contrast, those producing only a couple megawatts of electricity have considerably smaller hydraulic heads, even under 100 ft.

Flow

There is another factor involved with hydropower that’s important in understanding how hydroelectric power works. It’s called flow.

In simplest terms, flow is the volume of water passing a certain point in a specified amount of time. 

As an example of flow, imagine filling up a bathtub. When the flow rate is high, the tub will fill up fast. But when it’s slow, you could spend 20 minutes or more and still not fill even half of it up.

Using both concepts, here are some generalities about how hydroelectric power works:

• Water possesses more potential energy (which can be converted to more electricity) when both the hydraulic head and the rate of water flow are high.
• If a hydroelectric plant has a small rate of flow, it must have a huge hydraulic head to compensate in order to generate significant electricity. 
• If a hydroelectric plant doesn’t have great vertical elevation (meaning its hydraulic head is low), a very high flow rate can still generate substantial amounts of electricity.

Keeping this background in mind, here are the hydraulic situations for each major type of turbine that will produce the most electricity.

Hydroelectric power dams

There are many types of dams used in hydroelectric power. They serve to hold back water in reservoirs. Here are the major types of dams used today:

Type of Dam	Photo of Dam
Gravity
Arch
Roller Compacted Concrete (RCC)
Slab and Buttress
Embankment
Rockfill

What are the 4 main types of hydroelectric power?

The U.S. Federal Energy Regulatory Commission (FERC) categorizes hydroelectric power into four general types:

1. Conventional Impoundment (dam with reservoir)
2. Conventional Diversion (run-of-river)
3. Pumped Storage 
4. Marine and Hydrokinetic (MHK)

In this article, we focus on the first three types of hydroelectric power. For more information on the fourth type, see this article.

1. Conventional Impoundment (dam with reservoir)

The most common type of hydroelectric dam has a wide and deep reservoir of water behind it. These may be used as recreational facilities for picnicking, boating, or fishing.

The major similarity among all types of impoundment hydropower projects is that the powerhouse is close to the reservoir.

Here is a diagram of what a conventional impoundment hydroelectric plant looks like:

2. Conventional Diversion (run-of-river)

Hydroelectric power plants located on rivers where salmon and other fish species return from the sea for spawning going upstream frequently have fish ladders to allow returning fish to get through.

The fish ladders are situated close to the main water flow in a diversion channel. They are not literal ladders. They are bypass channels for fish to get to their ancestral spawning areas. 

Often in diversion dams, the powerhouse is located far from the reservoir, maybe even a few miles away.

Here is a diagram of a conventional diversion hydroelectric project:

3. Pumped Storage

Built mostly in the 1960s-1980s, pumped storage facilities are used to supply energy and/or water on demand to nuclear or fossil fuel power plants adjacent to them.

During off-peak periods when electric rates may be cheaper, water is pumped from a lower reservoir to a higher one. This is an energy-intensive process.

When electricity is needed (high demand), water is released to generate it. 

In 2021 in the U.S., there were only 23 TW hours of electricity created from pumped storage projects in 18 states out of 3,930 TW hours used. (1 TW = 1 trillion watts.)

Pumped storage systems use more electricity to pump water upwards than they produce. So, these facilities have net negative electricity generation.

Here is a diagram of a typical pumped storage hydroelectric setup:

4. Marine and Hydrokinetic (MHK)

Also referred to as tidal energy, marine and hydrokinetic energy use ocean waves, currents, tides, or inland waterways to generate energy.

So, no powerhouse or dam is necessary. An energy-generating apparatus (a turbine or similar) is placed directly in the water. 

The ocean’s kinetic energy or sub-surface pressure difference is transformed into electricity.

As of yet, MHK energy is still in its R&D phase.

Here is a schematic of one example of an MHK project:

FAQs about hydroelectric power

Here are a few frequently asked questions and answers about hydroelectric power. 

1. What are the top countries producing hydroelectric power in 2020?

The top four producers of hydroelectric power (in terawatt hours, TWh) in 2020: 

1. China (1,355)
2. Brazil (391)
3. Canada (382)
4. United States (286)

Note: One TWh = 1 billion kilowatt hours = 1 trillion watt-hours.

2. What is a microhydropower plant?

Green homesteaders, preppers, and small communities or businesses with a knack for DIY projects and a readily accessible stream or river on their property may consider building a DIY microhydro power plant as a source of off-grid renewable energy.

“Microhydropower can be one of the most simple and consistent forms or renewable energy on your property.”

United States Department of Energy (DOE)

In fact, the DOE has an entire page devoted to planning your very own DIY microhydro power plant!

A microhydro power plant usually generates 100 kW of electricity. Since the average household needs 5-6 kW of energy to run comfortably, a microhydro setup + battery storage could supply a small neighborhood, farm, or ranch easily. 

In conjunction with solar, wind, or geothermal energy, a microhydro system with battery storage would guarantee complete energy independence from the public utility grid. 

The type of hydroelectric power that works most sustainably and cheaply in micro form is a run-of-river system. Below is a diagram of the basic setup:

For more details on the nuts and bolts of such a DIY home energy project from start to finish, Manfred Mornhinweg in Chile documents his DIY adventures here.

Note: Even though the DOE didn’t mention it on their pages, be sure to get any necessary permits from your local jurisdiction before undertaking a DIY microhydro power project.

3. Can non-powered dams be converted to produce hydroelectric power?

It is possible to convert non-powered dams to produce hydroelectric power in some cases. Because these dams are older, they will require significant and costly renovation and retrofit. Whether it is economically feasible or not is questionable, especially in a climate crisis.

A group of researchers published a 2019 article asserting that due to environmental, safety, and cost concerns, there is a growing tendency in the U.S. to decommission aging dams or allow licenses to expire, including those with hydroelectric capacity.

The researchers hypothesized that photovoltaic (PV) panels could produce the equivalent amount of electricity generated today from hydroelectric power on only 13% of the land taken up by the reservoirs slated to be torn down. 

Furthermore, they calculate that if all the dams were removed and only 50% of the freed-up land was used by PV, the solar panels could produce over three times as much electricity.

This research suggests the heyday of hydroelectric power is over and solar power — the cheapest form of electricity in history — is here to take its place.

Monocrystalline vs Polycrystalline Solar Panel: What’s the Difference?

Are you looking to purchase solar panels for your home or business but feel overwhelmed by all the choices available today?

For instance, you’ve probably read about the differences between monocrystalline vs polycrystalline solar panels and wonder if these differences really matter anymore. 

While there are apparent contrasts between mono and poly solar modules, polycrystalline panels have recently undergone significant advances. Could polys be worth a more serious look for residential or business solar?

In this article on the differences between monocrystalline vs polycrystalline solar panels, find out everything you need to know about the latest upgrades to these residential and business solar options. We cover three types of differences:

1. Solar power output
2. Price per watt 
3. Carbon footprint

Our easy-to-understand tables of information on the differences between monocrystalline vs polycrystalline solar modules will help guide your purchasing decision

What are Solar Panels?

Have you seen sleek black or shiny blue glass-covered rectangular frames on roofs or on poles by highway construction sites?

Those devices are called solar panels. Other names for them are solar modules or photovoltaic (PV) panels.

Solar panels transform sunlight into direct current (DC) electrical energy that powers households, offices, or factories after inversion to alternating current (AC) electricity. Another type of panel may convert solar heat into thermal energy to warm water in pools or storage tanks.

In this article, we focus on solar panels that produce electricity.

What’s inside a solar panel?

Here’s a diagram showing the major layers inside a typical monocrystalline or polycrystalline PV module. Little has changed over time in the basic architecture of a solar panel.

What is a solar cell?

The workhorses of a solar panel are the multiple solar cells making up the central layer of a PV module as diagrammed above. 

In the illustration, solar cells appear as blue rectangles separated by silver metal lines called ribbons, busbars, or fingers. The rows of silver diamonds indicate the absence of photovoltaic material on the corners of every solar cell. The diamonds are the hallmarks of monocrystalline solar panels manufactured in cylindrical containers (see below). 

Inside the solar cells is where the solar-to-electrical energy transformation occurs.

The material responsible for the energy conversion in almost every solar cell on the market today is an ultra-thin silicon wafer composed of either:

1. A single silicon crystal (mono) of high purity and flawless structure; or
2. An irregular arrangement of multiple, imperfect and less pure silicon crystals (poly). 

In the case of poly panels, some of the impurities are various silicon-containing compounds that did not undergo chemical conversion to unadulterated, free silicon.

Added to the silicon in both mono and poly modules are tiny amounts — at a parts per million (ppm) level — of other chemical elements, especially boron and phosphorus. This process is called doping. (Note: Parts per million means out of a million silicon atoms, only a handful are atoms of other elements.)

It’s the presence of these boron and phosphorus “impurities” in silicon that makes it chemically unstable. This means some outer electrons can easily move to other atoms under certain conditions. Specifically, the boron has too few electrons to stabilize it in the crystalline structure. Silicon doped with boron is called p-type. 

On the other hand, phosphorus has too many electrons and isn’t stable in the crystalline lattice either. Silicon doped with phosphorus is called n-type. 

As a result of the unstable electronic configurations of doped silicon, certain electrons circulate freely throughout the silicon crystal lattice when solar rays (photons) possessing high enough energy levels hit them. 

In a properly doped solar cell, there is one side possessing an abundance of electrons and the other, a deficit of electrons (holes). The sun-excited electrons move in an organized way between these two ends at the p-n junction, forming an electrical circuit. 

In other words, the solar cell generates electricity in the presence of sunlight. This process is known as the photovoltaic effect.

Here is a diagram illustrating the inner workings of a solar cell:

What is a silicon wafer?

The silicon wafers (slices) in solar cells are like the microchips or integrated circuits used in all electronic devices including your smartphone or laptop. They serve as the substrate (base) for various materials and operations. Electrochemical reactions occur on the wafer in solar cells. Alternatively, electronic systems function on them. 

All silicon wafers are examples of semiconductors made of extremely thin slices of silicon. 

The thickness of a typical silicon wafer for a solar cell is between 100-500 micrometers (microns). For comparison, one human hair is approximately 180 microns wide. (1 micron = 0.00004 in.)

In the case of a silicon wafer used as the substrate for a solar cell, the entire surface of the wafer is functional in capturing sunlight and converting it to electrical energy. However, in monocrystalline modules, the diamond-shaped corners are excluded from energy production.

Here is a diagram of a typical solar cell:

Why is silicon used in solar cells?

Silicon is used in solar cells because it’s an excellent semiconductor. This means it doesn’t conduct electricity as well as metals like copper (thus the prefix semi, meaning half or partly). Nor does it insulate against (stop) electrical transmission like some other materials such as glass or wood. 

However, when certain substances are added (doped) to silicon, it becomes more electrically conductive. And it becomes able to convert one energy input (solar) into another (electricity). So it’s not an understatement to say that doped silicon serves as the cornerstone of the solar industry today.

Furthermore, in solar technology, one of the biggest advantages silicon has over other materials, especially metals, is that its resistance to electron flow decreases with increasing temperature. With the sun beating on solar panels thereby raising their temperature, you can understand why silicon is the preferred material in solar cells to generate and transmit electric current. 

The current just moves with less restriction in doped silicon inside sun-baked solar cells. Differences in the temperature coefficients of PV panels mean some are better than others at doing this.

How is silicon purified?

Silicon must be purified before it can be used as a semiconductor. Furthermore, since most silicon in nature is bonded with other elements, it must also be extracted from these chemical compounds. Elemental (free) silicon is mostly bound up in substances called silicates or as silicon dioxide (silica) in sand or atmospheric dust. 

Silicon purification: Molten salt electrolysis

So, to get solar-grade silicon from these compounds, molten salt electrolysis is a common, time-tested method to accomplish this. In this process, the silicon-containing substance in a molten state is literally split apart by an electric current, liberating silicon from its bonds with other atoms.

Silicon of 99.9% purity results from this technique which uses little energy, unlike other steps in making silicon wafers for solar cells. 

Silicon purification: Trichlorosilane intermediate

Today, another method is commonly used to purify silicon, though in a roundabout way. Initially, impure silicon is chemically transformed into a specific silicon-containing compound that can be more easily purified later by distillation because it is a liquid (unlike solid silicon in sand). That compound, trichlorosilane, acts as the chemical intermediate in this step. Then, further chemical reactions convert trichlorosilane back to silicon in a much purer state.

The final product, pure silicon, is almost ready to be made into wafers for solar applications.

What are the types of silicon crystals used in solar cells?

Solar grade silicon is crystalline. It is a solid at room temperature. The chemical symbol Si stands for the element, silicon.

There are four categories of bulk silicon that can be used in PV panels. During manufacture, they are formed into ingots, ribbons, or wafers. (Note: Ingots are oblong blocks of metal cast from a molten state.)

1. Monocrystalline silicon (c-Si)

The purest type of silicon, monocrystalline silicon is a single crystal cut from a cylindrical ingot in an energy-intensive process known as the Czochralski process. (The prefix mono means one.) When sliced thin, the wafer doesn’t fill an entire square of a solar cell, leaving gaps in all four corners. 

2. Polycrystalline (multi-crystalline) silicon (poly-Si, mc-Si)

Today, approximately 75% of poly-Si is commercially made by a modified Siemens process (see below). Or, leftover crystal fragments from c-Si manufacture can be melted together, forming poly-Si in a cube-shaped mold. (The prefix poly means many.) 

3. Ribbon silicon

A type of poly-Si, ribbon silicon is formed when molten poly-Si is physically stretched out to form flat, thin ribbons (films). This material is the basis of thin film solar panels.

4. Mono-like-multi silicon (cast-mono)

Taking the best of both worlds, small seed crystals of silicon are grown in the cube-like casting chamber used to manufacture poly-Si. Once grown, the interior of the resulting crystal is pure cubed c-Si but the exterior is of poly-Si quality with a greater number of impurities. Cast-mono panels do not have non-photovoltaic diamond corners.

How are silicon wafers for solar cells made?

Today, the solar industry uses different techniques to manufacture monocrystalline vs. polycrystalline silicon wafers used in solar cells.

Both begin with impure, molten polysilicon feedstock made by the Siemens process or by a fluidized bed (FB) method. In these techniques, a chemical such as trichlorosilane in gaseous form is placed around a silicon rod acting as a seed crystal. In FB, at the “moderate” temperature of approximately 1,382°F, trichlorosilane breaks down, freeing silicon atoms. Pure silicon lands on the rod, enlarging it.

Chunks of polysilicon result from the Siemens process. Polysilicon granules are produced through the FB technique. 

From molten polysilicon feedstock, monocrystalline silicon wafers are made through the Czochralski process (CZ-Si). Polycrystalline silicon wafers are produced via directional solidification (DS-Si) of polysilicon feedstock. Both of these methods are described below.

The major differences between CZ-Si and DS-Si involve:

• The way that polysilicon is melted 
• How the polysilicon is shaped into an ingot
• The size of the final ingot
• How the ingots are shaped into bricks for slicing into silicon wafers.

How are monocrystalline silicon wafers made?

Monocrystalline solar panels contain solar cells made from a single crystal — referred to as a monocrystal — of pure silicon (c-Si). This means the entire crystal lattice is continuous (unbroken) even up to the edges.

The Czochralski process (CZ-Si), also called crystal pulling, is the most common method used today in the solar industry to make monocrystalline silicon wafers used in solar cells. It is the least expensive way to grow large silicon crystals.

Invented by chemist Jan Czochralski, this technique begins with a sample of molten polysilicon. Doping (usually with boron) occurs in this early stage.

A silicon monocrystal is pulled out of the polysilicon material (called the “melt” once heated) by dipping a rod of a pure silicon crystal in the cylindrical container of the molten poly-Si. Slowly, it grows into a single, large, and highly purified silicon crystal that is pulled out of the melt by raising and rotating the rod.

This process may take several days to complete.

Finally, a wire saw cuts the resulting mono ingot into super-thin silicon wafers which are then polished and cleaned. During the cutting process, 40-50% of the silicon is wasted. It may be used to manufacture polycrystalline solar cells (see below).

Here is a diagram of the Czochralski puller apparatus: 

The Czochralski process is energy intensive, requiring high heat (2,574°F). Ingots up to 6 ft. long and 18 in. wide result. 

Prior to 2005, circular solar wafers cut directly from the cylindrical ingots were formed. Now, most ingots undergo trimming into “pseudo-square” bricks to reduce waste and costs (see schematic below). Nevertheless, the completed monocrystalline silicon wafers still have rounded corners devoid of PV material.

Approximately 5,000-6,000 monocrystalline silicon wafers are sliced from one ingot. 

Here’s a schematic of the entire process of making a monocrystalline solar wafer:

Monocrystalline solar grade silicon (Sog-Si) is not as pure as true c-Si needed to build electronics. Minor imperfections in the crystal lattice won’t affect solar performance like they would negatively impact the operation of sensitive electronic devices. 

To achieve even higher purity than CZ-Si affords, the float zone (FZ) process is used. Silicon wafers made from FZ are used in electronics.

How are polycrystalline silicon wafers made?

Polycrystalline silicon (poly-Si) is made up of numerous small silicon crystals known as crystallites. They may be the leftover crystal bits and pieces from c-Si manufacture melted down together. Usually at this stage of production, a tiny amount of boron is added forming p-type silicon.

In the directional solidification (DS) process, polysilicon feedstock is melted down in a short and wide, cube-shaped crucible. Through a temperature gradient, the bottom of the crucible cools before the rest. Gradually, purer silicon solidifies from the bottom up along with the temperature gradient. 

In the topmost molten part, most of the impurities reside. This part is not recycled back into feedstock, just like the bottom molten feedstock of the Czochralski cylinder is not.

From one DS ingot, 35,000-40,000 polycrystalline silicon wafers are cut.

Here’s a schematic of the DS polycrystalline silicon wafer manufacturing process:

In terms of crystal structure, polycrystalline silicon (poly-Si) is not as perfect as single-crystal monocrystalline silicon (c-Si). Nor is it like amorphous silicon (a-Si) that lacks a crystalline lattice of any significant size.

How is a monocrystalline solar cell made?

The manufacture of a monocrystalline solar cell begins with producing a single crystal of highly purified silicon through the Czochralski process (see above).

The cylindrical silicon ingot that results from that process is sliced ultra-thinly, washed, and polished into wafers. 

Phosphorus is diffused across the surface of the wafers creating the p-n junction needed for the operation of an electric circuit in a photovoltaic system.

To reduce the over 30% of light reflected off their flat surface, solar wafers are texturized through etching. This process allows light rays to refract off (bounce around) many surfaces, thereby increasing the chance for absorption and boosting PV efficiency.

Furthermore, the solar wafers receive an anti-reflective coating (ARC) such as silicon nitride. This layer reduces the reflection of sunlight off the PV modules back to space so more can be absorbed by the solar cells, enhancing panel efficiency. Incidentally, ARCs are often applied on eyeglasses, sunglasses, or camera lenses.

This graph shows how effective ARCs are in reducing reflection off of solar cells:

To boost electrical conductivity, silver alloy ribbons and backing are applied to the wafers. They are now finished solar cells able to convert solar energy to electrical energy.

Metal also connects solar cells in rows and columns, forming the sheet of solar cells (usually 60+) encased in the middle layer of a solar panel (diagram above).  

How is a polycrystalline solar cell made? 

Polycrystalline solar cells could be made in one of two ways.

First, the Siemens or FB process (described above) produces relatively pure molten polycrystalline silicon. Instead of inserting a silicon rod as a seed crystal on which a single large silicon crystal forms (as in the Czochralski process), the melt is left to cool via a temperature gradient in a cube-like container. Once the melt hardens, leaving molten impurities on the top, a cube-shaped ingot of polycrystalline silicon remains, ready to be wire cut into wafers.

Alternatively, miscellaneous silicon crystal shards left over from the manufacture and cutting of monocrystalline silicon are melted together in a cube-like mold with a small quantity of boron, then resolidified. The resulting silicon block is cut into thin wafers (slices) of p-type silicon. 

To form the critical p-n junction on a p-type silicon wafer, n-type dopant (like phosphorus) is diffused across the front surface.

Next comes the anti-reflective coating (ARC). As its name implies, this layer reduces the reflection of sunlight off the PV modules back to space.

In other words, the coating increases the absorption of radiant energy which leads to greater solar panel efficiency.

Today, ARC is often the chemical silicon nitride or boron nitride. Silicon or titanium dioxide are alternatives. It is applied to the module through a process called plasma-enhanced chemical vapor deposition.

To increase solar absorption further and boost solar panel efficiency, the silicon wafer may be texturized. This means its surface has been “roughened up” a bit to increase surface area on which solar rays can hit and to allow them to refract back on adjacent PV material.

Previously, only c-Si could be textured. But due to technological improvements, poly-Si can be textured today. This is another way differences between monocrystalline vs polycrystalline panels are becoming less important.

Finally, the silicon wafer is made into a solar cell by adding metal connections to the back and front. Using a silver paste, grid-like fingers and busbars are screen-printed on the surface. A full metal plate or grid is applied to the back.

To complete the metal connections and form electrodes in direct contact with the silicon wafer, the paste is heated at a very high temperature. In this manner, the passageway for electrical current is embedded in the silicon wafer. 

A solar cell is born.

How are monocrystalline solar panels made?

After monocrystalline solar cells are prepared as described above, large numbers of them (typically 60 or more) are electrically connected together with wire or metal ribbons. Together, they make up the central layer of a solar panel.

The distinctive nature of a mono PV panel are the silver diamonds running along the columns of solar cells. Once a cylindrical (round) wafer from the ingot is placed on a square sheet, all four corners are devoid of photovoltaic material. 

Encased in protective EVA plastic and placed under a glass cover with a backsheet all inside a metal frame, the PV module is complete.

Here is a schematic of the entire process:

How are polycrystalline solar panels made?

Square polycrystalline solar cells are prepared as described above. Large numbers of them (60+) are connected together with wire or metal ribbons forming an electrical circuit.

A sheet of solar cells is encased in protective EVA plastic and placed under a glass cover. Inside a metal frame and resting on a backsheet, the PV module is ready to generate electricity.

What are the superficial differences between monocrystalline vs polycrystalline solar panels?  

Superficial differences between monocrystalline vs polycrystalline solar panels relate to the appearance of the PV modules.

Monos are black and characterized by solar cells with rounded edges. Polys have rectangular blue solar cells, giving them a bright, speckled look.

What are the solar power output performance differences between monocrystalline vs polycrystalline solar panels? 

In terms of the characteristics that affect the solar power output performance of solar panels, differences between monocrystalline vs polycrystalline panels are not as pronounced as they once were.

Here is a summary table of monos vs polys graded on key performance metrics. These factors play significant roles in how well PV panels produce electricity. 

Here’s a brief explanation on each of these parameters:

1. Solar panel efficiency

In the simplest terms, efficiency is a measure of how well PV panels convert sunlight into electricity. The theoretical maximum efficiency of conventional monos and polys is approximately 33% (Shockley-Queisser Limit). 

2. Temperature coefficient of a solar panel

The temperature coefficient indicates how well a PV module withstands increases in temperature. The smaller the absolute (numerical) value (ignoring the negative sign which means reduction in efficiency), the better the panel. 

3. Degradation rate of a solar panel

Degradation rate shows how quickly PV panels will break down due to normal (mostly climatic) processes. A smaller rate is better.

Note: For more information on efficiency, temperature coefficient, and degradation rate, follow the hyperlinks given above.

Do the solar power output performance metric differences between monocrystalline vs polycrystalline solar panels really matter?

In 2022, the solar power output performance metric differences between monocrystalline and polycrystalline solar panels are so small compared to what they once were that these differences don’t really matter anymore.

As the table above suggests, it is possible today to buy a top-of-the-line poly that is performance competitive with a standard mono, especially in terms of efficiency.

Especially if you live in an area with moderate-to-cool temperatures (northern latitudes), the slightly higher temperature coefficient won’t have a huge effect on power output in a polycrystalline panel. Likewise, many types of heat-induced degradation will be minimized.

What is the price per watt difference between monocrystalline vs polycrystalline solar panels? 

If you’re a home or business owner in the market for solar, you’ll be quoted price per watt by companies vying for your money. This difference between monos and polys has narrowed considerably over time. In fact, currently, there is significant overlap between them. It’s fair to say monocrystalline vs polycrystalline solar panels are price competitive in 2022 — and going forward!

For a year-by-year history of the differences in price per watt for monocrystalline vs polycrystalline solar panels, the International Energy Agency has an excellent interactive tool. The last four values shown in the table below are from this source.

The shrinking gap in price between monos and ploys mirrors the overall drop in price of residential solar systems. Ten years ago, in 2012, it was $5.04/watt. In 2022, it’s $2.94/watt. 

Does the price per watt difference between monocrystalline vs polycrystalline solar panels really matter?

The prices of both monocrystalline and polycrystalline solar panels have plummeted in recent years. Now, some monos are price competitive with the best polys. 

If roof space is not a huge factor, polycrystalline panels may be your solution. However, by choosing high-efficiency polys, even the size of your roof won’t matter in many cases.

What is the carbon footprint difference between monocrystalline vs polycrystalline solar panels? 

The amount of greenhouse gas emissions generated by the manufacturing of a solar panel is known as its carbon footprint.

The greater the quantity, the larger the contribution to our climate crisis from the panel’s production.

Note that for all PV panels on the market today, precious metals are needed. This requires fossil fuel-intensive mining and extraction. Environmental damage often results. 

Does the carbon footprint difference between monocrystalline vs polycrystalline solar panels really matter?

The carbon footprint of monos is higher due to the intense heat required for several days during the making of each batch of silicon crystals. Fossil fuels are burned to produce this energy. The burning increases carbon emissions, fueling our climate crisis.

Additionally, the manufacturing process for monos is very wasteful of this energy. Approximately 40-50% of silicon manufactured in this way does not go into making c-Si modules. It is discarded. Some of it may go to produce polys.

Most PV panels are made in China where over 67% of all energy comes from fossil fuels, primarily coal (55% from coal in 2021). Plus, there are emissions from long-distance transport to other countries where the panels are installed.

Carbon-conscious home and business owners who wish to tread lightly on the Earth may opt for USA-made polycrystalline panels instead of Chinese-made monocrystalline PV modules.  

Key takeaways on monocrystalline vs polycrystalline solar panels

Given all the choices today between monocrystalline vs polycrystalline solar panels, homeowners and businesses need to consider the latest technological developments before making their purchase.

Although monos have long been thought to be the best solar panels you could buy, this may not be the deal breaker for you especially if you’re budget-conscious and weighing prices per watt.

Or, if you’re a green consumer, carbon footprints of solar panels may really make a difference to you, in which case polys fit the bill.

Today, some polys power perform almost as well as monos — and for a lot less money and a lighter carbon footprint, too.

In 2022, homeowners and businesses alike have plenty of great solar options between monocrystalline vs polycrystalline solar panels. Begin your research with this article. Then, continue it with related resources and reviews on solar energy on this website.

Or possibly you’re worried about the effects of heatwaves or other climate extremes on the functioning of your local power grid.

Power failures aren’t any fun. They may even be deadly.

To achieve energy security and independence, as well as to offset high energy bills, more and more homeowners are considering residential solar or solar & battery storage — both of which are on the rise in the United States.

Naturally, you’re wondering if the solar power output from a rooftop or ground-mount solar array would be adequate to meet all of your family’s energy needs without breaking the bank.

In this complete guide to solar power output, you’ll find out everything you need to know about how much energy a solar panel produces. Then, you’ll be able to make an informed decision about whether a residential solar energy system is right for you.

How much energy does a solar panel produce?

People who ask how much energy a solar panel produces often want to know if one photovoltaic (PV) panel can make a certain appliance run. 

The short answer is: depends on the appliance and the panel’s power rating.

If you’re thinking about going solar for an RV or camping trip, you definitely must know how much energy a solar panel produces.

If you miscalculate, you could be in a tight spot.

But if you’re considering a solar setup for your home, you also need to know how much energy a solar panel produces.

Like all appliances, solar panels are rated in watts. Watts are a unit of electrical power and noted by W.

One thousand watts equals one kilowatt (kW). Expressed another way: 1,000 W = 1 kW.

Watts and watt hours explained: Refrigerator example

As an example to explain what the watts unit of measurement means, think of an older, large refrigerator. It may be rated at 1,000 W. (Check the label to find yours.)

The conventional understanding of wattage means the appliance consumes 1,000 watts of electrical power to run for one hour. 

Another way to express this is to say it takes 1 kilowatt hour (kWh) of electrical energy to run a fridge rated at 1,000 watts for one hour.

But this explanation is inaccurate. (And it’s relevant to solar panels, too, if you’ll stay with me.)

In reality, a manufacturer’s label refers to the output wattage of the appliance. What a motor-driven appliance like a refrigerator actually needs to get started to operate (that is, the input wattage or starting surge) will be higher than what’s on the label.

The reason for this difference between input and output wattage is partly due to the inefficiency of an appliance in converting incoming electrical power to outgoing work. In other words, some energy is lost to the surroundings as heat or sound during normal startup operation.

In the case of a fridge, the outgoing work is keeping food cold or frozen.

Depending on the age and brand, a refrigerator rated at 1,000 W will need a greater startup wattage or power surge — 2,000 W or more — to do 1,000 W worth of keeping foods cold or frozen.

You can check out exactly how much energy is used by your appliances with a Kill A Watt meter.

P3 Kill A Watt Electricity Usage Monitor

CHECK LATEST PRICE

You may be wondering: What does this have to do with solar panel power ratings?

A solar panel manufacturer will rate solar panels by wattage just like appliance makers. Today, most residential PV modules are rated at 300-450 W each.

This is the output wattage of solar panels. It’s the amount of electrical power a solar panel can be expected to generate when exposed to the sun for one hour under ideal conditions.

It’s also called a power rating.

However, there is also an input wattage of a solar panel. Although there is no motor in a PV panel that requires a power surge to get started like you saw with the refrigerator example, there is a huge input wattage for solar panels.

It comes from the sun and is called irradiance (brightness).

Irradiance

The amount of solar power coming from the sun and landing directly (perpendicularly) on a surface measuring one square meter (approximately 3 ft.²) is called irradiance. It’s measured in W/m².

After passing through Earth’s atmosphere where it reflects off airborne particles and scatters or is absorbed by air molecules, a portion of the sun’s rays eventually reaches the ground (or your rooftop solar array).

When scientists measure irradiance at a location on the equator on a cloudless day while the sun is at its highest point in the sky, (called solar noon), they find the irradiance to be approximately 1,000 W/m² (1 kW/m²). This value refers to solar power at “full sun” or “peak sun” and is called a peak sun hour.

Here’s a graph that illustrates how peak sun varies with the seasons:

Irradiance and peak solar power output: Summer vs. Winter

The graph above explains why solar panels can produce more output wattage during the summer vs. the winter. There is simply more solar irradiance (in watts per square meter) during longer periods of summer days.

However, this general conclusion is oversimplified.

Solar panels function best when it’s cool. Then the electrical connections between solar cells and those linking panels together won’t get overheated. If they do, the wires offer greater resistance to electrical transmission from the roof (or backyard for a ground mount system) into your home.

In the summer, although irradiance is more intense, your panels are too hot to produce their maximum energy output. 

The temperature coefficient of the panel determines how much energy will be lost. Depending on panel quality and the temperature, it could result in a 16% loss or more in energy production. The temperature coefficient is also on the spec sheet.

However, don’t automatically assume that PV panels have greater solar power output during the winter.

Although it’s colder, there’s yet another problem that hinders optimal solar power output.

The angle of the sun’s rays on your panels in the winter are far from direct (perpendicular). This poor angle decreases solar absorption of less intense sunlight.

So, solar power output in the winter will be reduced compared to what it could be if the solar rays hit the panels at a perpendicular angle.

How can I maximize solar power output? The effect of seasonal changes

The ideal way to overcome high heat issues in the summer and angle concerns in the winter as much as possible is to use solar tracking.

In this method, PV panels move during the day, tracking the sun as it makes its trajectory across the sky and keeping the modules perpendicular to the solar rays’ impact. 

Alternatively, if you can’t afford solar tracking, a ground mounted solar array that’s adjustable to meet the sun’s position in the sky and approximate perpendicularity through the seasons is preferable to rooftop solar where the modules are fixed (stationary) at one angle.

Elevated and angled on poles in a ground mount system, the panels receive the sun’s rays more directly. After angle adjustment, there will be better solar absorption and, thus, greater solar power output.

Here is a helpful guide from an experienced solar installer to know which angle is best for your solar system depending on the season and your location.

How much energy does a solar panel produce in the summer vs. the winter? An example using irradiance

Here’s an example that gives you an idea of how irradiance determines solar panel output wattage. 

Based on the graph shown above, you calculate the amount of energy a solar panel can produce in the summer or winter using the irradiance and estimated number of peak sun hours in your location.

How much solar power output is possible in the summer?

According to the graph above, peak sun at 900 W/m² lasts for 6 hours a day in the summer. (This is an average.)

900 W/m² x 6 hrs = 5,400 Wh/m² = 5.4 kWh/m² = 5.4 peak sun hours
(Since 1 kWh/m² = 1 peak sun hour, there are 5.4 peak sun hours in an average summer day.)

For a 400 W solar panel that’s one square meter in area, exposed to direct sun for 6 hours under ideal conditions:

400 W x 5.4 peak sun hours = 2,160 Wh/day

So, a single 400 W solar module that’s one square meter in area could run a 1,000 W refrigerator for an hour (assuming the startup power surge is under 2,160 W. An extra 400 W panel contributing another 2,160 Wh/day would eliminate any doubts).

However, since you need the fridge 24/7, even though the motor cycles on and off, a battery backup or connection to the utility grid is essential. 

How much solar power output is possible in the winter?

From the graph shown previously, peak sun at 500 W/m² lasts for three hours in the winter. (This is an average.)

500 W/m² x 3 hours = 1,500 Wh/m² = 1.5 kW/m² = 1.5 peak sun hours
(Since 1 kWh/m² = 1 peak sun hour, there are 1.5 peak sun hours in an average winter day.)

For a 400 W solar panel that’s one square meter in area, exposed to direct sun for 3 hours under ideal conditions:

400 W x 1.5 peak sun hours = 600 Wh/day

So, a single 400 W solar module could not run a 1,000 W refrigerator by itself in the winter. 

You’d need four additional PV panels (400 W each) for the refrigerator to run reliably off of these solar modules in the winter for an hour and handle the startup power surge. If you did, you’d have 5 x 600 Wh = 3,000 Wh/day.

Since you need the fridge for more than an hour every day, battery storage or grid connection is necessary.

The caution note given above applies here, too.

Key takeaways about solar power output from the irradiance example

If you live in an area with greater peak sun hours, a smaller-sized solar system — in terms of total output wattage — will provide you with all or most of the solar power output you need to meet energy demands. 

By contrast, if you live in a region with fewer peak sun hours, you’ll need a larger solar system to cover all of your energy needs.

Although this example is simplified, it tells you how irradiance and sun hours directly determine solar power output of a residential solar array. 

This example allows you to estimate how much energy each solar panel produces (output wattage) based on the sun’s brightness (irradiance) in your area.

How to use sun hours to calculate solar power output

To simplify the calculation for the amount of energy a solar panel produces, solar companies may simply use sun hours based on irradiance.

There are sun hour maps which you can consult to get a more precise value for various times of the year in your region. The resource maps by the National Renewable Energy Laboratory are excellent.

The higher the output wattage of a PV panel and the more peak sun hours in your area, the greater amount of electricity your system will generate.

For example, California and Arizona receive 6-8 sun hours per day. For Alaska and New York, it’s only 3-4 sun hours/day.

Alternatively, you could use NREL’s PVWatts Calculator for more precise information. Input your address to get yearly and monthly peak sun hours. 

Multiplying the output wattage by the number of sun hours in your location gives you the total energy produced in one day, expressed in watt hours, under ideal conditions:

Energy (Wh) = Labeled Output Wattage (W) x Sun Hours (h)

However, basing your estimate of the grid-tied solar array size that’s right for you on this value will lead you to purchase a system that’s too small to meet all your energy needs.

The reason for this is that the panels’ labeled output wattage was established during ideal conditions which rarely occur in the real world.

As a general rule of thumb, assume that real-world conditions (including cloudy or snowy days and hot weather) will lower the actual energy produced by a PV panel by approximately 25% over the course of a year.

A cloudy day, for instance, can lower solar power output by 20%! Dirty panels can reduce it by 6.5%.

As an example using the 25% loss, a 400 W solar module exposed to 4 sun hours per day will produce:

400 x 4 x 0.75 = 1,200 Wh = 1.2 kWh of electrical energy each day on average over the course of a year.

Not 400 x 4 = 1.6 kWh per day.

Although there may be cold, sunny days when your solar panels generate more than their labeled wattage, don’t expect this to happen frequently enough to counteract the loss of power on hot or cloudy days.

To meet your energy needs, be sure to factor in a 25% loss of solar power when sizing a grid-tied solar array for residential or business purposes using spec sheet output wattage. (Note: Off-grid solar calculations are different.)

Even with the loss of solar power due to non-ideal conditions, there is enough of it to power the world with solar energy alone 10,000 times over:

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If only humans could figure out how to capture all that energy and use it efficiently.

What are the savings on electric bills from solar panels?

According to the U.S. Energy Information Administration, the average cost of electricity in 2021 was approximately 14 cents/kWh.

So, for example, a 400 W solar panel in a location with 4 sun hours, assuming a 25% reduction in power output due to non-ideal conditions, can generate 1.2 kWh per day. That’s equivalent to 14 x 1.2 = 16.8 cents from a single PV module every day.

If you have 24 solar panels of the same wattage in your rooftop or ground mount solar system, that’s 24 x 16.8 cents = $4.03 per day shaved off your electric bill.

In a month, that’s a savings of $4.03 x 30 = $120.96.

For a year, that comes to $120.96 x 12 = $1,451.52.

Although a solar setup may not generate the same power all year long (due to weather, dirt, shade, poor angle or orientation, or just normal degradation) you can count on significant savings on electric bills when you go solar as long as the sun shines.

How many solar panels are needed to fully power a home?

An average household in the United States uses approximately 30 kWh of electricity every day. 

To give you an idea of how many panels you’d need in a rooftop or ground mounted solar array to generate 30 kWh per day in a region with 4 sun hours and using 400 W panels that produce 1.2 kWh each (assuming a 25% power reduction due to non-ideal conditions as shown above):

30 / 1.2 = 25 PV panels

To find out how large an area of space you would need to install an array of 25 panels, consult the panels’ spec sheet for their spatial dimensions and do the math. A 5 x 5 array (five strings of five modules each) is the logical choice. But if you have an irregularly shaped roof, you may arrange the 25 panels differently.

Although it’s possible to generate enough solar power to run an entire home anywhere, you may need many more higher-wattage PV panels in northern states where there are fewer sun hours. 

By contrast, in sunny southern locations, fewer panels will suffice to power a home, and they may not have to be high wattage either.

How is the output wattage of a solar panel calculated?

Solar manufacturers use irradiance, under standard test conditions, known as STC, to determine the output wattage (power rating) of their solar panels.

These conditions are:

• 1000 W/m² irradiance
• PV cell temperature of 77°F (while air temperature is 32°F)
• Absolute air mass spectra (a measure of atmospheric thickness) of AM1.5 

STC is what you see on the label and the specification sheets with a tiny asterisk beside it indicating a footnote.

To put it into ordinary language, STC is like a clear, windless, bright winter’s day.

That STC asterisk on a spec sheet tells you the solar company replicated the environmental conditions (STC) to get 1,000 W/m² as the input wattage in a laboratory setting. Then they measured their panels’ output wattage (power rating) under those conditions. 

In reality, at other locations on the Earth on any particular day when the standard conditions are not met, irradiance may be significantly less — possibly as low as 200 W/m²!

And even though the air temperature may be mild (68°F), the PV cells could be burning up at 50-90°F hotter in direct sunlight. This could easily cut 20% off of energy production.

The diagram below illustrates why ground mounted arrays have an advantage over rooftop solar: heat can dissipate under the panels to keep PV cell temperature under control and prevent huge power loss.

When they’re installed on a roof, there isn’t sufficient space under them to allow the panels to cool off. 

In the real world, 52% of all incoming solar radiation is lost. Some of it goes back into space or is randomly scattered or absorbed in the atmosphere.

In addition, approximately one third of the solar radiation that actually arrives at Earth’s surface and hits a photovoltaic cell inside a solar panel is not absorbed by the PV cells and converted into electrical energy.

The reason it’s not absorbed is that these photons (light energy) from the sun don’t have the correct energy level to knock off electrons in the silicon of the PV cells. The knock-off process is how solar energy is converted into electrical energy.

Instead, these photons are simply absorbed as thermal energy or released as heat energy.

Does efficiency determine wattage of a solar panel?

Because the solar energy conversion to electrical energy is not perfect, solar cells are not too efficient at making electricity.

Today, top-of-the-line solar panels have 23-24% efficiencies. 

The efficiency of a solar panel does not determine its wattage.

So, you will find on the market 300 W panels of 23% efficiency and 400 W panels of 16% efficiency. 

The higher a PV panel is rated for wattage, the more electricity it can generate, whatever its efficiency may be. How well a solar module converts sun energy (that is, its efficiency) is already taken into account during the testing process to rate its output wattage. 

Why is it important to know solar power output?

If you’re in the market for a rooftop or ground mount solar system, solar companies will quote you an estimated price.

They will most likely base their estimate using a dollar per watt metric. 

According to the Solar Energy Industries Association, in 2021, the price per watt of a residential solar array in the United States was approximately $3.05/watt.

For a typical U.S. solar system size of 6 kW (6,000 W), that will come to:

$3.05 x 6,000 W = $18,300 before tax incentives

Because of the Biden Administration’s Inflation Reduction Act passed in August 2022, there will be a 10-year extension for the federal solar investment tax incentive at 30% of installation equipment costs until 2032. Then it will step down to 26% in 2033 and to 22% in 2034.

Solar power output: The role of voltage and current

When a solar manufacturer measures a panel’s output wattage with a device called a digital multimeter under standard test conditions, they plot a current (I) vs. voltage (V) graph like the one below to arrive at the maximum output power point (MPP or P_MP):

The maximum solar power output (P_MAX) — located on the graph where the curve bends — is defined by this equation: 

P (watts) = V (volts) x I (amps)

In words, power measured in watts equals voltage measured in volts multiplied by current measured in amps.

On a PV panel’s specification sheet, you’ll find numerical values for many of the quantities shown on the graph above.

For example, here are data taken from the spec sheet of Trina Solar’s 380 W solar panel:

Since P_MAX = V_MP x I_MP, 

380 W = 40.3 V x 9.43 A

The higher the electrical currents and voltages produced by a solar panel, the greater will be its output wattage. All panels will show a similar curve as the one above.

The brighter the sun (that is, the greater irradiance) hitting the panel, the higher the electrical current passing through it will be. 

Incidentally, the efficiency of a solar panel (also listed on the spec sheet) is calculated based on the P_MAX value generated under STC. 

Efficiency is equal to the ratio between the maximum power generated per unit area of the panel, (P_OUT), and the incoming power, expressed as a percent:

Efficiency (%) =  P_OUT / P_IN = [V_MP x I_MP /Area of PV cell] /P_IN x 100

Under STC, the incoming power (P_IN) is the irradiance of 1,000 W/m².

FAQs about solar power output

Here are a few commonly asked questions and their responses about solar power output and how much energy a solar panel produces.

Will a solar panel rated at a certain wattage always produce that amount of solar power?

Unless ideal conditions are met all the time (direct sun falling perpendicularly on the photovoltaic cells on a cloudless, cool day), solar panels will rarely produce their stated wattage on a regular basis. 

The angle of the panels, their directional orientation, the air temperature, the temperature at the panels, the temperature coefficient, and the degradation rates all have major effects on exactly how much energy a solar panel produces.

To increase the likelihood of maximum solar power output, purchase high-quality PV panels using the latest technology with a solid warranty from a reputable company. Then match them with a top-of-the-line inverter and charge controller that can handle that level of solar power output.

Of course, make sure that their angle and orientation toward the sun are optimal. And that they’re dust- and dirt-free, away from shading by trees or buildings.

High efficiency of the panels is not a guarantee that your panels will achieve optimal solar power output. So, for instance, while monocrystalline panels are more efficient than polycrystalline modules, if their rated wattages are the same, their solar power outputs should be the same, too.

However, more efficient solar panels will have lower degradation rates, meaning they’ll last longer while still performing at 90% of their initial power output even after 20-25 years of energy production.

What is NOTC and PTC on a solar panel spec sheet?

When a solar manufacturer measures how much energy a solar panel can produce, they use standard test conditions (1,000 W/m² irradiance, 77°F, and AM1.5) noted as STC replicated in a lab setting.

There are other test conditions — called NOTC or PTC — used to determine a PV panel’s power output. Some solar manufacturers may include this information on their spec sheets.

NOTC

Sometimes, a company will also test their panels under NOTC, which stands for nominal operating cell temperature. These are defined as:

• Irradiance of 800 W/m²
• Air temperature of 68°F
• PV cell temperature of 113°F
• Wind speed of 2.2 mph

NOTC offers a glimpse into a panel’s output wattage variability under a certain set of real-world conditions. Sometimes, NOTC ratings could show a negative difference of 100 W or more from the manufacturer’s stated output wattage under STC.

The discrepancy is often due in part to the power loss at higher temperatures. It’s not unusual to lose 15-20% of power output when it’s hot outside, especially with inferior panels whose temperature coefficient is high. 

This is why you should expect a panel’s power performance to be at least 25% lower on average, over time, than whatever the labeled wattage is. 

Likewise, expect at least a 25% reduction in the total power output that you calculate based on labeled wattage of a rooftop or ground mount solar array consisting of 16-30 panels. (Of course, there are exceptions to every rule, but this is still a good general rule of thumb.) 

PTC

Another way to test solar panels for output wattage is using PTC. This is an abbreviation for PVUSA test conditions. 

PTC is defined as:

• Irradiance of 1000 W/m²
• Air temperature of 68°F
• Tested at 30 ft. above ground level
• Wind speed at 2.2 mph
• Air mass spectra of 1.5

California uses PTC when it calculates rebates as part of the California Solar Initiative (CSI) Program. 

PTC is considered to be more like conditions in the real world than STC.

Does the wattage of a solar panel determine its size?

Strictly speaking, a PV panel’s wattage does not determine its size. Thus, you can find PV modules on the market rated 100 W up to 450 W, and all may be approximately the same size in total area.

On the other hand, the efficiency of how well a panel converts sunlight into electrical energy partly determines panel size (in terms of total area) for a desired output wattage.

For example, a high-efficiency (23%) module rated at 300 W will most likely be smaller than a lower-efficiency (17%) panel also rated at 300 W.   

However, a solar panel of 18% efficiency may have an output wattage rating of 300 W while a higher-efficiency module, of the same size, can produce 400 W.

So, greater solar energy conversion to electrical energy is possible on a smaller area in a solar panel of higher efficiency.

This is why, when space is a limiting factor, high-efficiency panels rated at 375-450 W will require less roof or backyard area, even if your energy demands are great (8-12 kW solar system rather than the typical 5-6 kW array). 

You will need a larger surface to support more lower-efficiency panels of the same or lower wattage in similarly-sized solar systems. 

The trend among PV panel manufacturers these days is to increase both efficiency and power performance of solar panels by making individual photovoltaic cells larger and often splitting them in two (half cell technology). The larger cells are placed on larger panel sizes. 

So, instead of the traditional 6-inch solar cell, today you’ll find 6.5-, 7.2-, or 8.3-inch cells. There may be 60 or 72 (or, in the case of half-cell technology, 120 or 144 cells, respectively) of these larger cells arranged on a single module. 

Bigger cells require larger panels with more PV cell surface area. Half cell technology capitalizes on this fact. 

In other words, in a panel with 120 or more half cells, the electric current going into each half of one photovoltaic cell is also halved. The reduction of current lowers resistance to electrical transmission, and, subsequently, reduces energy losses. So, there is an increase in output wattage and often in panel efficiency, too.

Key takeaways on solar panel power output

It’s fairly straightforward to calculate how much energy a solar panel produces by the formula below:

Solar panel wattage (W) x Number of sun hours (h) = Solar energy output (Wh) 

However, there are many factors that determine whether a single solar panel will produce its rated wattage. The most important factors include:

• Number of sun hours in your area
• Local weather and climate conditions
• Panel angle and orientation toward the sun
• Temperature coefficient of the panel
• Degradation rates of the modules
• PV cell technology

Typically, an average American household will have 16-30 panels of 300-450 W each in a solar system located on their roof or in the backyard. Depending on the panels’ wattage and their number, the total size of the array will be approximately 5-12 kW. When weather and climate cooperate — and barring major malfunctions — this amount of solar power output can meet or surpass your family’s energy requirements.

Energy your solar system generates that you don’t need may be sent back to the public utility grid in grid-tie systems. In most states, homeowners receive an energy credit for this through net metering programs. 

Or, you may opt to install a solar + storage system in which case the energy you don’t use immediately is stored in a battery until you need it (like when the electric grid fails or when electric rates are highest).

In both scenarios, the solar power output of your residential solar system will lower your home energy bills and go a long way toward achieving carbon-free energy independence for you.

So, naturally, you want to know how long solar panels last before you take the plunge.

Here in our solar panel lifespan guide, you’ll find out everything you need to know about how long solar panels last.

Fortunately for budget-conscious homeowners, there are many ways — both before and after purchasing a rooftop or ground mounted solar array — that you can extend your solar panel lifespan.

Get the full scoop here on the average solar panel lifespan and how to make your solar panels last longer.

How long do solar panels last? Average solar panel lifespan

The best indicators for determining how long solar panels last are the performance and the product (materials/workmanship) warranties that solar manufacturers offer when you purchase their photovoltaic (PV) panels. 

These documents represent the manufacturer’s promise regarding the power output and quality of their solar panels over time. The warranties protect homeowners from receiving PV panels that don’t generate as much energy as they claim to, or are defective in any way.

Until this year, the standard performance warranty offered by top tier solar module makers was a guarantee of 25 years of energy production at 80% or higher of their stated output.

The product (in terms of materials and workmanship) warranty was a guarantee for 10 years in most cases.

Sample calculation for a solar panel lifespan

As an example of how you use warranty information to figure out how long a solar panel lasts, consider a typical residential PV panel rated at 300 watts (W).

According to a standard solar panel performance warranty, a 300W solar panel is guaranteed to produce at least 300W x 0.80 = 240W at 25 years post-installation. (80% = 0.8.) If it under performs while the warranty is in force, you’d be eligible for a replacement.

Likewise, if a panel developed microcracks in its third year, even those barely perceptible to the naked eye but enough to reduce energy production, you would be eligible (in theory, at least) for a free repair or replacement.

While these are still the warranty parameters followed by the majority of solar manufacturers today regarding the best way to know how long solar panels last, one solar company raised the bar concerning how long solar panels last in 2022.

SunPower and the 40-year solar panel warranty

In the beginning of 2022, solar giant SunPower announced a 40-year warranty on their Maxeon Interdigitated Back Contact (IBC) panels in select countries including UK, France, Germany, Australia, Mexico, and Japan. 

At the time of this writing, United States residents are not eligible for the 40-year performance warranty by SunPower. For them, the customary 25-year performance warranty is offered. 

SunPower’s IBC modules are high-performing because of advanced technology that eliminates traditional, front-side metal ribbons through which electrical energy moves on its way inside your house. IBC panels situate these ribbons on the back where sunlight interference isn’t an issue (except on bifacial solar panels). 

So, the front sides of IBC modules offer more surface area for sun exposure, unhindered by metal ribbons running throughout. Consequently, they produce more energy than their counterparts with customary and widespread metal ribbons over the panel’s face.

SunPower’s 40-year warranty includes these features: 

• Minimum power output of 98% of panel’s wattage rating in the first year 
• Maximum panel degradation of 0.25% per year for the following 39 years 
• Workmanship and materials covered 
• Servicing needed to repair, replace, or refund defective panels

After calculation, this means there is 88.3% guaranteed power output at the end of 40 years. (See the next section for more information on degradation rate and how to calculate estimated power output using it.)

So, these top-performing solar panels can continue to generate 80%+ of their stated output well after 40 years of use. What an attractive proposition for energy-conscious homeowners!

What happens if my solar company goes out of business before my warranty expires?

If your solar panels last longer than the company that installed them, but a problem normally covered by their warranty arises, you are out of luck — unless the company made other arrangements to cover the warranties of its existing customers.

But don’t count on it.

Fortunately, it’s possible to insure your residential solar system with an independent insurer to avoid a potential catastrophe like a bankrupt solar company just when you needed them.

In fact, you will receive a new warranty longer and more comprehensive than the original from the now-defunct solar installer.

Be sure to read the fine print before signing on, though. Only select solar module and inverter manufacturers are covered.

What is solar panel degradation? 

Solar panels undergo several natural degradation processes by which their power performance drops over time and which shortens the average solar panel lifespan. These include:

• LID: Light-induced degradation (from initial and continuous exposure to sun)
• PID: Potential-induced degradation (due to voltage leakage)
• LeTID: Light- and elevated temperature-induced degradation (poorly understood but distinct from LID)
• Microcracks (physical damage)
• Hotspots (localized overheating) 
• Panel deterioration or malfunction (front and/or back, due to water penetration or corrosion)
• Discoloration (weather effects)

Most of these degradation effects usually occur slowly over time. When not corrected early, they will get progressively worse, potentially resulting in huge power losses.

LID, however, usually results in a 2-3% power loss immediately after a solar array goes live for the first time and lasts for several days until the degradation rate is stabilized, typically below 1%. 

In the factory, manufacturers may compensate for expected light-induced degradation by increasing the actual power output of its panels by about 5% above what the panels’ spec sheet rating is. But, due to continued LID over the modules’ lifetime, the output won’t stay elevated for very long.  

LeTID, on the other hand, could occur suddenly and result in an approximately 10% loss in power performance.

Tips on how to estimate a solar panel lifespan: degradation

Top-of-the-line solar panels suffer less degradation than inferior panels. In general, the more expensive a solar module is, the lower its degradation rate.

But to be sure, always check the panel’s specification sheet for expected degradation rates when comparison shopping for PV panels. 

Before buying, ask your prospective solar company for data on degradation for the PV modules you’re considering, including data based on real homeowner experiences.

What is a solar panel degradation rate? 

According to the National Renewable Energy Laboratory, the average solar panel degradation rate is 0.5% per year. This value reflects the amount of expected power loss each year by the PV modules because of normal deterioration. 

It’s an average percentage meaning it could be slightly higher or lower. A degradation rate of 1% is possible for low-quality, inexpensive PV panels.

As a rule of thumb, the degradation rate is usually higher than the average 0.5% in hotter climates and in rooftop systems vs. ground mount PV arrays.

For certain types of degradation, such as light-induced degradation (or LID), the power loss may be substantial only in the beginning when your PV system goes live, then taper off in the following years.

Each year, most solar panels lose a small amount of output capacity by comparison with the previous year. In most cases, high-quality PV panels don’t suffer as much degradation as their inferior competitors over their lifespan.

Sample calculation: Effect of solar panel degradation rate on power performance

As an example, consider a small 5 kW rooftop solar system. Assume that the panels degrade at 0.5% per year (0.5% = 0.005). 

This means — ideally on a cool day with 5 hours or more of direct sun — your 5 kW solar system can produce approximately 5,000 watts (5 kW) of electricity every hour (1 kW = 1,000 W). 

At peak functioning for 5 hours, that’s the equivalent of 25,000 Wh per day (25 kWh).

So in one year, your 5 kW system yields 25 kWh/day x 365 days = 9,125 kWh (rounded down to 9,000 kWh for the rest of this example for ease of calculation).

Note: In reality, your solar array will not perform at its peak every day due to weather fluctuations. This example assumes for the purposes of illustration that it will.

At the end of your array’s first year, accounting for initial light-induced degradation (LID) of 2% (see previous section):

Output capacity: 9,000 kWh

Degradation loss: 9,000 kWh x 0.02 = 180 kWh; [2% = 0.02].

So, your system’s baseline output capacity is no longer 9,000 kWh per year at the end of year 1.

Due to LID at the start of operation, it becomes 9,000-180 = 8,820 kWh. This is what it can produce when functioning at peak level in the beginning of the system’s second year.

Then, repeating this calculation for the second year using the average degradation rate of 0.5%, you get a little bit more degradation:

Starting output capacity: 8,820 kWh

Degradation loss: 8,820 kWh x 0.005 = 44.1 kWh

Thus, you begin the third year of energy production with 8,820 – 44.1 = 8,776 kWh as the maximum possible for solar energy production.

The calculations repeat for each year as shown.

For this example, after 25 years (the end of most warranties), with a 0.5% degradation rate each year after accounting for an initial LID loss of 2% in the first year, these calculations terminate with an approximate 12% loss of initial, theoretical maximum power performance of 9,125 kWh.

Put another way, after 25 years, your solar panels will retain about 88% (100-12%) of their original output capacity when their degradation rate is the industry’s current average of 0.5% per year.

That’s still a very high level of energy production after a quarter century of use! 

Fortunately, no extreme power degradation is expected after that — unless there’s a bizarre weather event. 

But even if there is extreme weather in your area, your solar panels may still last longer — unlike your roof — as the photo below illustrates.

Your solar panels will never suddenly turn off at the 25- (or 40-) year mark when their warranty expires. They will last longer than that.

At that mark, they will just produce less energy compared to earlier years of operation. In cases of good-to-high quality PV panels, the energy drop is around 88% of what it was when you first turned your system on.

How do you know when it’s time to replace “spent” solar panels?

The solar industry states that solar panels are considered “spent” when they’re at the end of their warranty coverage period or producing less than 80% of the energy output they had in their first year of operation.

Because some solar companies are offering 30- or 40-year warranties on their PV panels, there is no need to replace or discard your solar array even after 40 years unless your energy needs have significantly increased by more than 20% of what they were when you had initially installed your solar system.

The reason for this recommendation is that although solar modules will lose a small portion of power performance during the warranty period due to normal degradation, it will likely never fall under 80% of their stated wattage by the warranty’s end. 

The sample calculation in the previous section, based on a 25-year warranty, showed this to be true.

Expressed another way, for homeowners with typical 200W to 400W panels, this means you’ll still get at least 160W to 320W from each panel, respectively, at warranty’s end, barring freak accidents or a faulty inverter.

200W x 0.8 = 160W. 400W x 0.8 = 320W; 80% = 0.8.

The same rule of thumb applies no matter the length of the warranty (25 years is most common).

This rule also doesn’t depend on the size of your solar system (in terms of wattage or in terms of the number of PV modules).

The good news, as you’ve seen in the preceding section, is that solar panels will continue to create electricity — although at a reduced level — even after their warranty expires.

By using a solar performance monitoring system such as Solar Analytics, you’ll be able to tell at a glance (or a phone swipe) how well your panels are generating electricity for you over time.

If you’re still at 80% power performance 10, 20, or 30 years post-warranty expiration, then there certainly is no need for a new solar installation. This is true especially if your original solar installation was larger than needed to compensate for potential production loss due to cloudy or snowy days when energy output will be sub-optimal.

Furthermore, if your energy needs have dropped after 40+ years — for example, due to becoming an empty nester once your grown children move out — your original solar system may meet your reduced demands even if it’s functioning only at 75% capacity.

Is solar panel recycling common in the United States?

Unfortunately, solar panel recycling is not common in the United States today.

Currently in the United States, 90% of used (spent) solar panels are landfilled. That amounts to 50,000 still-functional PV panels every day! As you’ve seen from the sample calculations above, this represents an enormous quantity of energy…thrown away.

Discarding PV modules that retain significant electricity-generating capacity is not an example of a good human-environment interaction, especially if you’re striving to live a zero-waste, sustainable lifestyle.

Plus, it’s a huge amount of bulky solid waste with numerous hazardous components. 

Fortunately, there is active research into solar panel recycling today. It just hasn’t become widely utilized commercially yet. 

3 ways to reuse spent solar panels

When you decide it’s time to make a change in how you produce solar energy at home — whether it’s 30 or 50 years after first installing rooftop solar — you have several options for dealing with the spent solar panels. 

You may wish to:

• Enlarge your existing solar array by adding new panels to make up for the natural energy loss due to degradation of your original installation.

• Donate the spent panels to an organization that will install them elsewhere to offset energy costs for a qualified family or business.

• Recycle them (although this is not yet common practice in the United States and so it may not be readily accessible to you).

Do solar inverters or microinverters last as long as solar panels?

The “brains” of your residential solar array is the solar inverter (also called a string or central inverter) located on the ground level of your home (inside or out), or the microinverters situated under or close to the solar modules in the solar array. 

These devices are responsible for converting the DC electric current that the solar cells in the solar panels create from sunlight to AC current that’s used by most appliances in your home.

If your solar system is connected to the public utility grid or to a battery backup for storage, the inverter will channel excess electricity your array produces to one, the other, or to both.  

Most solar inverters on the market today are warranted for an average of 10 years. Some inverter companies offer warranty extensions. 

Today, microinverters may have longer warranties, even equal to those of solar panels (25 years). However, be sure to read the warranty fine print. It may not cover everything, such as the wall or communications equipment, for the same length of time.

Do solar panels last longer than solar inverters?

Most solar inverters are warranted for a shorter time compared to the PV panels. Predictably, most solar system failures occur with the inverter as the following graph shows:

So, since the lifespan of solar panels is often more than twice that of your inverter, plan on replacing the inverter once, twice, or even more for your array. It depends on the length of time past your PV panel’s warranty expiration that you wish to benefit from their reduced energy performance.

When you need a new inverter, it’s the perfect time to consider switching to microinverters and/or power optimizers if you’re thinking about it.

Note that research shows that both central and microinverters perform similarly in terms of power performance despite widely accepted claims that microinverters operate better.

3 ways to extend solar panel lifespan

Solar panels do not have moving parts. This means it’s easier (and cheaper) to make them last longer compared to wind turbines.

There are three key ways to maximize the longevity of solar panels and ensure that they’re producing  as much energy as they should be.

1. Solar panel performance monitoring

Even though you cannot see your solar panels actually converting solar rays to electrical energy by looking at them, it’s possible to verify that they’re functioning correctly.

You can do this by monitoring their energy output in real time through an app on your phone or a program on your laptop. 

Solar inverter manufacturers usually provide this capability when you purchase their products. Your solar installer will get you connected at the time your solar system goes live.

With the right setup, you can monitor a PV system remotely when you’re away from home.

Here’s a sample graph that an app or web portal generates so you can monitor solar panel power performance over time:

When connected to the internet, the data can be sent to the solar company that installed them. 

If there’s a drop in production over time, or a change in any given month compared to the same time in previous years, your solar company can alert you. Scheduling an appointment to troubleshoot the issue will rectify the situation to prevent further performance loss.

2. Solar panel cleaning 

Proper cleaning can help to extend solar panel lifespan. There are professional solar panel cleaning companies ready to assist you on a regular basis. This service can be expensive.

Fortunately for budget-conscious homeowners, solar panel cleaning may not be necessary.

If you’re in an area that receives regular rainfall, solar panel cleaning is not needed.

On the other hand, if you’re in a drought-prone area with heavy urban air pollution, frequent dust storms, or prolonged wildfires, it will be necessary to clean your solar panels often.

When covered by dirt and debris, solar modules will suffer major performance setbacks.

Using a low-pressure garden hose — never a high-pressure power wash — is sufficient. Gently wiping them down with a soft cloth that doesn’t leave tiny bits of material behind is optional.  

However, if your water is hard, (i.e., contains a large amount of minerals), using distilled water is preferable. This way, you’ll avoid leaving mineral deposits on the glass surface that impede sun ray penetration to the solar cells under the glass where electricity is created.

Similarly, if you live by the ocean, periodically remove the salt deposits from ocean mist that dries on the solar panels.

Research is underway to develop self-cleaning solar panels, saving you both time and money.

3. Professional solar panel assessment

With many communities experiencing extreme weather events worsened by our climate crisis, it’s prudent to schedule a solar panel inspection post-storm, especially if your performance software indicates a problem.

Qualified solar technicians will be able to check for damage and perform emergency repairs or replacements.

Hopefully, when done quickly, you won’t suffer too much loss of solar power production.

When a solar panel service call is needed, and when it’s not

In cases where your solar power monitoring data look normal after an extreme storm with gusty winds or hail, you may still wish to schedule an assessment. 

Tiny microfractures or loosened electrical connections could have occurred. Without a rapid fix, these issues could worsen over time and require a major repair later.

On the other hand, your monitoring system could suggest there’s a serious problem when there really is none. Sudden drops in energy output could be caused by your inverter — not your solar panels.

We’re not referring to a utility grid power outage that will also shut down your solar array. (At times like that, you’d wish you had a solar battery backup for storage!)

Solar inverters have undergone technological improvements making them extremely sensitive to all electrical disturbances that are out of the ordinary.

These events may result in a temporary shutdown of your solar system. This often occurs when an inverter detects utility grid surges during high-usage times (like a heatwave). 

When this happens, you’ll see a momentary drop in power performance. It will resolve itself once the grid returns to normal. 

If you notice this, give it 12-24 hours before calling a solar technician. Then do so only if the problem persists.

You’ll save a lot of money and avoid an expensive service call for nothing. 😉

Ways to increase energy production from your solar panels

Sometimes, people asking about solar panel lifespan really want to know how they can optimize their solar panels to increase energy production for as long as possible. 

There are several characteristics of solar panels to take into account when you wish to get the most energy from them for the longest possible time.

1. Low degradation rate

The degradation rate discussed earlier is an important metric to judge how long solar panels last. Choose panels that have a degradation rate of 0.5%/yr. or less.

2. High-efficiency solar panels

In order to limit the effect of degradation rate on energy production, purchase high-efficiency panels. These often have the lowest degradation rates on the market. They are also the most expensive modules you can buy.

The good news for consumers is that the price of solar modules has plummeted by 99.6% since the 1970s with no end in sight. 

Monocrystalline solar panels are the most efficient solar panels available today for homes, as well as the most expensive. Their efficiencies may be as high as 23-24%.

3. Low temperature coefficient

High-efficiency solar panels are very good at converting sunlight to electricity. Their low temperature coefficients (available on the spec sheet) is part of the reason why.

This means they do not experience significant drops in energy output when it’s hot outside like poorer quality solar panels do. 

Tip: Be sure your installer leaves 2-3 inches between your roof surface and the metal racking securing your PV array in place. This space will permit airflow under the panels, cooling them off. To ensure the highest power performance, it’s important to keep the panels as cool as possible.

Research is underway to develop self-cooling solar panels, making it even easier to decrease power loss due to elevated ambient temperature.

Once you’ve decided on high-efficiency solar panels with a low degradation rate and a low temperature coefficient, there are still other ways you can optimize energy production for as long as the power warranty lasts — and beyond (see #4 below.)

4. Setting up solar panels for optimal energy production

To get the most energy from solar panels for as long as possible, their placement angle and orientation in relation to the sun are critical.

Facing due south

Ideally, arrange your solar panels so that they are directly in front of the sun when the sun is at its highest point in the sky. This orientation corresponds to an azimuth angle of 180 degrees.

If your roof is not south-facing, a ground mounted system may work better for you. You’d be able to set up a solar array facing due south (space permitting) on your property.

Avoid solar panel shading

Both trees and buildings could block all or part of your PV panels at some point during the sun’s trajectory in the sky each day.

Microinverters will minimize this issue.

Use the optimal solar panel tilt angle

The manner in which your solar panels are tilted in relation to the sun is important in increasing the power production of your solar panels. This is known as the tilt (elevation) angle.

Ideally, you want your solar panels to receive incoming solar rays directly perpendicular to your PV modules for maximum energy production.

For solar panels that are stationary (do not track the sun), it is common to hear that a tilt angle of 15 degrees added to your latitude in winter or subtracted from your latitude in summer, or simply an angle equal to your latitude, is the best for optimal power performance from solar panels. 

This advice is too general and won’t result in a solar setup optimized for peak power performance all year long.

According to Charles Landau who has done extensive research on optimum tilt angles for solar panels, the best tilt angle for fixed rooftop solar can be found by calculating:

• If your latitude is below 25°, use the latitude times 0.87.
• If your latitude is between 25° and 50°, use the latitude, times 0.76, plus 3.1 degrees.

Homeowners with ground mount systems have more flexibility. They also have a greater ability to optimize their array’s tilt angles at any time. They may adjust the tilt angle to correspond with the seasons as the position of the sun in the sky changes over the course of a calendar year.

For people who are restricted to having just one tilt angle for their rooftop solar system, choose the one for the season where your energy needs are greatest (or most costly, depending on where you live). 

Use the PVWatts calculator by the National Renewable Energy Laboratory to find out precisely what the optimal tilt angle is for your solar array at a given time during the year.

Highlights on solar panel lifespan

It’s easier to see a quicker return on investment on your rooftop solar system by investing in solar panels that possess:

• High efficiency
• Low degradation rate
• Low temperature coefficient

Solar panels that possess these superior characteristics come with the longest performance and product (materials) warranties available today. 

Forty years (with 80%+ performance) is the latest warranty length for PV panels. Twenty-five years is standard.

It’s also important to set up your solar modules in a way that maximizes their energy production, no matter their starting efficiency. 

To succeed, set up your array (rooftop or ground mount) so that solar modules:

• Are facing due south
• Have a tilt angle appropriate for your location
• Use a high-quality inverter (or microinverters) for DC to AC current conversion

During their lifespan, you can ensure best performance of your solar modules by:

• Monitoring energy production in real time through an app
• Cleaning them when needed
• Checking their condition after heavy storms by hiring a solar company to assess their condition

When you follow the recommendations given above, it’s likely that your solar panels will last longer than their warranties claim they will. 

They will produce clean energy to meet some or all of your home energy needs for many years — even decades — longer than you had imagined they ever could. 

If you’re a homeowner or business owner looking to make the switch to renewable energy — and enjoy the substantial energy savings that come with it — it’s helpful to get comfortable spotting key information about solar panel size and weight from reading those spec sheets. 

So, when solar companies present you with pages of mind-numbing calculations to prove to you why their proposal is the best, you’ll understand them better and choose the best one for you.

In this article, you’ll find out everything you need to know about solar panel size and weight. Sample calculations using solar panel size and weight for homes and businesses will help you estimate exactly what you need.

Plus, you’ll learn about various factors that directly impact the performance of your residential or commercial rooftop solar array. These are important to consider when planning out your solar setup size dimensions using solar panel size and weight so you’ll maximize solar power at the lowest cost. 

There’s no surprise in learning that other data on the solar panel spec sheet (besides solar panel size and weight) are important when including those factors in a solar array performance assessment.

We got you covered on that, too.

Solar panel size and weight guide

Since the number of solar panels you need to meet your energy requirements is a major determinant of your upfront installation cost, knowing the size of the modules is critical to lowering your cost. 

In other words, your goal in looking up the dimensions and figuring out how many panels you need to meet your energy requirements is to find the fewest number of panels that will suffice.

This is especially true if you have limited roof space, large energy demands, and/or a small budget.

In general, you want highly efficient, small panels to reduce costs.

Fortunately, solar module weight is not a huge factor in achieving this objective as long as you have a roof in good condition.  

More on this below.

How big are solar panels?

When you look at a solar panel data sheet, go to the section titled Mechanical Properties, Mechanical Data, or something similar to find out how big solar panels are.

This information is often in tabular form. It may appear as a labeled diagram.

In a table, you will find solar module dimensions usually given as length times width times height (LxWxH) in millimeters (mm) or inches (in). Consider height to be the same as depth (thickness). 

On a diagram, you can read the dimensions directly. They will be shown with double-headed arrows like this:

Usually, residential rooftop solar panels are approximately 65 inches tall, 40 inches wide, and 2 inches thick. In feet, that would be 5.4 ft. by 3.3 ft.

Commercial solar modules are usually slightly larger in length and width only.

However, with greater technological innovations in recent years, there is no longer a clear cut distinction between solar modules for private residences vs. those for businesses. 

Because of all the changes in the solar world, it is no longer as simple as adding the dimensions of a greater number of individual solar cells making up each panel (usually each one is 6 in. by 6 in.) to a “residential” panel’s size to determine a “commercial” panel’s size.

Since every manufacturer is different in how they present information on their data sheets, it’s also not clear whether the dimensions of the panel frame (if there is one) are included in the LxWxH measurements. (Usually, frames today are 1-2 in. wide.)

So, it’s always a good idea to ask manufacturers exactly how they size their panels. This is especially true if you have severe space restrictions. 

Or, you may have local code regulations stipulating how much unobstructed space around the perimeter of a solar array you must have (for maintaining roof access during a fire). 

The additional frame dimensions (if there are any) probably won’t enlarge your solar system too much, but it’s good to err on the safe side. Ask questions before signing a contract.

Solar panel size chart 

The line between residential and commercial panels in terms of solar panel size (length and width) is blurred as the chart below illustrates.

This chart provides typical size dimensions of several representative solar panels of popular brands sold today using various types of solar technology.

Some solar companies will use the terms residential and commercial on their websites, but others will not. 

So, when surfing the web, assume that panels designated as neither residential nor commercial could work for you.

In the cases of non-designated solar modules, it’s more important to examine the spec sheets to see how well particular panels will perform and how well they will fit on your roof or on your property as a ground-mount system according to the amount of solar power you wish to generate. (See below for more on calculating this.)

How much do solar panels weigh?

To find out how much solar panels weigh, consult the spec sheets again. The weight (in pounds or kilograms) should appear in the same table of mechanical information (or properties, data) where you found solar panel size dimensions.

Today, residential solar panels weigh approximately 42 pounds. Commercial solar panels weigh approximately 50 pounds. But again, there is no hard and fast rule nor an industry standard.

Here is a table of representative solar panel weights from popular brands.

Can my roof support solar panel weight?

Homeowners or business owners may think that 20+ solar panels will weigh too much on their roofs and compromise its integrity. Surprisingly, this is not true in most cases.

The reason why most roofs can support a solar array is that the total weight is evenly distributed over a large surface area. This means there is little additional weight per square foot.

The Insurance Institute for Business & Home Safety publishes a summative roof guide and regularly updates it. It contains information on codes and standards from many of the major international and national regulatory organizations which establish building codes and standards.  

In that document, there are links to the major organizations stating that typical asphalt shingle or wooden roofs can bear up to 20 ft. per square foot. Clay tiled or metal roofs may hold up to 27 lbs. per square foot. 

As a ballpark guesstimate, if your solar array was designed to house 20 panels weighing 43 lbs. each, the system would weigh 43 x 20 = 860 lbs. Mounting hardware adds more weight depending on materials. Usually, lighter aluminum is the material of choice. 

For a 20-panel array, the hardware may add up to 200 lbs. to the combined weight of all the solar panels. This varies, of course, based on the size of the solar panels as well as the hardware material. 

So, those 20 modules spread over an estimated roof area of 400 square foot (see example below), subject your roof to the equivalent of (860 + 200) / 400 = 2.65 lbs. per square foot.

This is well below the maximum acceptable load (20 ft.²) for a typical roof.

However, if your particular solar panels were so extremely efficient or powerful that you needed only one or two small but heavy modules to meet all of your energy needs, this standard would not apply. Then you’d have to consider the effect of a concentrated load on one small area of your roof.  

Building codes are different for concentrated loads. Then you’d need a certified contractor or mechanical engineer to sign off on your proposed array first to avoid a hole in your roof due to a concentrated load.

On the other hand, if your roof is in poor shape, very old, or structurally damaged in any way, it is a good idea to consult with an independent engineer or contractor first for peace of mind before you install a setup of any solar panel size or weight to avoid an accident.

For more information, check out our post on the solar panel roof load calculator.

Roof age and timing of a rooftop solar installation

Another consideration regarding the installation of a solar array no matter the solar panel size or weight is the age of the roof’s shingles. If they’re approaching their functional limit, it would be more economical and easier to replace the shingles before installing a solar array. 

This way, before the panels’ normal lifespan (25+ years) is reached, you won’t need to uninstall the panels in order to replace the shingles when they need to be, then reinstall the solar array later on a brand new roof.

How many solar panels do you need? 

To figure out how many solar panels you need, it’s essential to know two things:

1. Your average energy requirements 
2. How much of that demand you want met by solar energy versus the public utility.

Calculating your average energy requirements

To determine how much energy you require, add up your electricity usage — stated on electric bills — over the past year. The value is expressed in kilowatt-hours (kWh). 

As a rule of thumb, the average household in the United States in 2020 used approximately 11,000 kWh of electricity annually. That works out to be about 900 kWh per month.

Determining how much solar energy you want to meet your total energy needs

If you want to get 100% of your electricity from your solar system, you need to factor in the expected loss of power production due to weather variability. Then add to your actual energy usage when doing the calculations.

This way, you’ll never fall short on electrical power.

For example, it’s possible to lose up to 90% of energy production on cloudy days. Solar “soiling” from dust and other particle pollution may cause an additional 7% drop in energy output in the United States.

So, to figure out the size of the solar system that will meet your needs given the energy losses you will encounter due to variable weather, adjust your energy demand to be approximately 25% higher than what it actually is.

This way, you’ll decrease the impact of low energy production weather conditions on your calculations and never be without power.

So, using the national average: 900 kWh x 1.25% = 1,125 kWh per month. (You need this value for the next step.)

Since this value is only an average, there will be some months when you use less, and some months where you use more.

If neither of those conditions apply to you, you definitely want to use your solar array to generate less than what you require so you’ll never overproduce. But, you should still take into account the weather-related losses by adding 25%.

So, for example, if you only want your solar array to produce half of your home’s energy requirements, perform a calculation similar to the one above. 

But, you’d use 75% (50% + 25%) of 900 kWh (the national average) or whatever your home’s monthly average is: 900 kWh x 0.75 = 675 kWh. 

Use this value to figure out the size of your solar array.

Determining how much solar energy you will likely generate

To determine how much solar energy you will generate, you need to figure in the number of hours of direct sunlight you get everyday.

This number varies depending on many factors, including your location, the tilt of your panels, and their orientation to the sun. (More on these below.)

The best way to get the number of direct sunlight hours is to use an online calculator called PV Watts.

A simpler alternative is to consult this map:

It could be 3-6 hours per day, but usually it’s 4-5 hrs./day in the continental USA.

Calculating your solar array size in kilowatts (kW)

Finally, with the numbers you calculated above, you can figure out the solar array size you need in watts every month. 

Solar array (kW) = Monthly electric usage / (direct sun hours x 30) 

For the example above: 1,125 kWh / (5 hrs. X 30) = 7.5 kW

So, for the average household that wants 100% of its energy created by the sun, their rooftop solar array must be 7.5 kW in size.

Calculating your solar array size in terms of the number of panels

In this step, you will find out how many solar panels your 7.5 kW solar system requires. Knowing their dimensions, you can then figure out the roof area you need to support them.

Solar panels are rated in watts (W). For a home or business, they typically range from 100 W to 400 W. For this example, assume you’re interested in a 375 Watt solar panel.

Since the solar system size found in the preceding step is expressed in kilowatts and 1 kilowatt equals 1,000 watts, the equation becomes:

Number of solar panels = Array size x 1,000 / panel wattage

Using the numbers found here: 7.5 kW x 1,000 / 375 W =  20 panels

So, you’d need an array of 20 solar panels, each one rated at 375 Watts to meet all of your energy needs.

Computing the roof area of your solar array

The architecture of your particular roof will determine the placement of the solar panels.

In this example, 20 modules could be mounted in several different ways such as:

• Two rows of ten
• Five rows of four
• Four rows of five

Assuming panel dimensions (in inches) of 65x40x2, a 5×4 array has the area: (65 x 5) x (40 x 4) = 325 in. x 160 in.

Expressed in feet: 325 / 12 = 27 ft.

160 / 12 = 13.3 ft.

So the rectangular array will be 27 ft. long and 13.3 ft. wide with a 2 in. thickness. Its area = 27 x 13.3 = 359 sq. ft.

Businesses calculating the roof area needed for a solar system would perform similar calculations using their own (probably larger) numbers. 

Factors that influence solar production & the number of solar panels needed 

As mentioned previously, there are several factors that influence how much solar energy your rooftop solar array will actually produce. These factors, in turn, partly determine the number of solar panels you need.

Ultimately, it’s your roof size which will dictate what the final result will look like.

The United States Environmental Protection Agency (EPA) developed a helpful document titled Solar Photovoltaic Specification, Checklist, and Guide. It discusses many of the factors that influence solar energy production.

Here are some of the pertinent points from that Guide you need to take into account to maximize the success of your home or commercial solar project:

• Assume 500 sq. ft. for a 5 kW array (1 kW/100 sq. ft.). If using energy-efficient appliances, a smaller area will suffice.

• Roofs situated directly (due) south receive the most direct sun. This is the best orientation. If the roof is more than 45 degrees off from due south, energy production will be very diminished. You should consider a ground mount system instead.

• The tilt angle of the array should match the array’s geographic latitude in degrees. Other sources adjust this value slightly. This is referred to as the inclination of the solar array.

• Conduct a solar shading study using a sun path tool such as Solar Pathfinder or Solmetric SunEye to determine the impact of shading (if any) on energy production.

Other factors that influence solar panel energy production

Besides these factors, you should take into consideration the efficiency of solar modules on the market today to convert solar energy to electrical energy. 

Today, the efficiency ranges from 8-12% for first-generation thin film panels. It goes up to 23-25% for PERC or CIGS. 

Monocrystalline panels may achieve a 18-22% efficiency.

Also, solar modules with small temperature coefficients close to zero (also on spec sheets) perform better in hot regions.

Note that all panels decrease efficiency over time through natural degradation rates, but some are better at maintaining optimal functioning compared to others. 

This information is also listed on solar panel spec sheets.

Carefully review warranty terms to estimate a panel’s efficiency over its projected lifespan and compare with the warranties of other panels you’re considering. 

The longer the warranty for power production, the better the panel in most cases.

Key takeaways on solar panel size and weight

When considering rooftop solar for your home or business, it’s important to consider solar panel size and weight.

If you’re limited on roof space, have shading issues or sub-optimal orientation, choosing more efficient panels is better. They can produce greater wattage for their (typically) smaller size. This means you won’t need as many to get the same energy output as less efficient (and possibly larger) panels. 

On the other hand, with a large usable roof area, you can sacrifice high efficiency — and save on startup costs — when you buy larger panels at a lower cost per panel. You’ll enjoy the same energy output as fewer, higher-efficiency solar modules would provide. 

If you’re a business with extensive roof space, cheaper thin film panels that take up a lot of space may serve you well.

By using information from solar panel spec sheets about solar panel size and weight to your advantage, it’s easy to design a solar array that will perform well at less cost to you no matter your specific situation and needs.