# How hot do solar panels get? Effect of temperature on solar performance

Solar panels are often exposed to high amounts of heat, especially during long, hot summer days. In this article, we will discuss the impact hot weather has on solar panels, and how those effects are mitigated by consumers and manufacturers alike.

## How hot do solar panels actually get?

Home solar panels are tested at 25 °C (77 °F)  and thus solar panel temperature will generally range between 15 °C and 35 °C during which solar cells will produce at maximum efficiency. However, solar panels can get as hot as 65 °C (149 °F) at which point solar cell efficiency will be hindered. Install factors like how close the panels are installed to the roof can impact the typical heat of your solar system.

The majority of solar panels are composed of silicon photovoltaic (PV) cells, which are protected by a sheet of glass and held together with a metal frame. Those materials are comparable to the materials that make up the windows and frame of a car – to understand how hot solar panels get, think about a car that’s been sitting in a hot parking lot on a summer day. The windows and frame will be hot to the touch, but there’s little danger of burns or fire. The actual temperature that your solar panels will be at a given time varies significantly depending on air temperature, how close you are to the equator, level of direct sunlight, and roof material.

## The effect of temperature on solar panel efficiency

Homeowners considering solar often wonder, “can solar panels overheat?” Just as with any other electronic equipment, solar panel performance does decline as they get hot – the laws of thermodynamics tell us that with increased heat comes decreased power output, and this applies to solar panels. Thus, warmer temperatures will always means less output for PV cells, and this loss is quantified in a “temperature coefficient” by panel manufacturers, which varies from model to model.

How can you know what kind of output losses your panels are experiencing? Manufacturers rate their products’ susceptibility to temperature in the form of the temperature coefficient, which is expressed as a percentage per degree Celsius. It is standard practice to test solar panels for power output at 25 °C. So, if a panel is rated to have a temperature coefficient of -0.50% per °C, that panel’s output power will decrease by a half of a percent for every degree the temperature rises about 25 °C (77 °F). Although that number sounds small, the surface temperature of a dark-colored roof in the summer can be significantly higher than 25 °C – imagine the surface of an asphalt road on a hot summer day. The small percentage of output power loss for each degree of heat compounds.

Here’s an example: if you have solar panels with an efficiency rating of 17 percent and a temperature coefficient of -0.45, they will lose 0.45% of their efficiency for every degree above 25 °C. If the surface temperature of your roof increases to 30 °C (86 °F), your solar panel’s efficiency will fall to 16.7 percent. If it increases to 35 °C (95 °F), efficiency falls to 16.3 percent.

## How to counteract solar panels overheating

Regardless of which panels you decide to use, there will always be some energy output loss due to heat. However, there are several ways to mitigate the effects of hot temperatures on solar panels. A basic technology employed by most panel manufacturers is to use a thermally conductive substrate to house their panels, which helps vent heat away from the glass layers of the module. Solar panels are also commonly mounted a few inches above your roof, with airflow space below the actual unit, helping to move heat away from the modules as well.

Thin film panels are a recent market innovation, and boast a temperature coefficient rating of between a -0.20 and -0.25. These panels have a distinct coefficient rating advantage over more traditional monocrystalline and polycrystalline photovoltaic panels, which have a temperature coefficient typically between -0.26 and -0.50. However, they come with a trade-off – thin-film panels are typically less efficient than their crystalline PV counterparts.

An important note to keep in mind about temperature coefficients is that if a panel is operating in temperatures lower than 25 °C, the temperature coefficient will actually be positive, and your solar panels will increase in efficiency. This means that the best conditions for optimal solar production are cold, sunny days, which in turn means you don’t have to live in a warm climate to benefit from solar power. This efficiency gain in cold weather helps to offset losses that occur during the summer months, especially for homeowners living in regions with distinct winter/summer weather cycles.

Conversely, if you do live in a climate that is warm and sunny throughout the year, you may want to invest in higher-end solar panels that come with a lower temperature coefficient. Sunpower, Panasonic and REC manufacture solar panels with some of the lowest temperature coefficients available in the industry. If you expect that the surface temperature of your roof will climb above 25 °C for a significant portion of the year, consider getting quotes from solar installers who offer these higher-end panels.

## Get the right solar setup for your home

Solar installers customize their system designs to meet the specific needs of each individual property, which includes the temperatures a roof might expect to see throughout the year. However, if you are considering installing solar panels on your roof, finding the installer that’s the right fit for your home may take a little browsing around. You can use the EnergySage Solar Marketplace to easily solicit and compare multiple offers from solar installers near you. If you have any questions or concerns about hot weather, simply add a note in your profile when you register.

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Jacob is a researcher and content writer at EnergySage, where he's an expert on current issues–and new technology!–in the solar industry. With a background in environmental and geological science, Jacob brings an analytical perspective and passion for conservation to help solar shoppers make the right energy choices for their wallet and the environment. Outside of EnergySage, you can find him playing Ultimate Frisbee or learning a new, obscure board game.

## 32 thoughts on “How hot do solar panels get? Effect of temperature on solar performance”

1. Hardy

There’s no denying that solar panels are specifically built to withstand high temperatures. It is natural for them to get hot because I install them in a location where they freely absorb the sun’s heat. 🙂

2. GDS

Its seems like they didn’t answer the question because it goes against their agenda. Solar panels absorb 90% of the suns energy, but we only get on average 16% of that back in the form of electricity. Depending on the angle of the panel to the suns rays 60-80 % is converted directly into heat. I haven’t seen any reports or investigation on how this impacts the environment. Another area that engineers or science is silent about is producing hydrogen! The only green way to produce hydrogen is through electrolysis, but is uses almost twice the power to create the hydrogen. Its practical only as an expensive power storage for some applications. On some message boards (yahoo) you cant even type this without having it removed for being false info!

3. Edward L Hensel

so if solar panels absorb the heat from the sun, how much heat is generated back into the atmosphere? Wouldn’t a large solar farm used commercially for power generate a large amount of heat back into the atmosphere warming the atmosphere?
I’m curious is the temperature outside of a solar panel farm with hundreds if not thousands of panels be the same temperature outside of a solar farm?

1. kat

I find it concerning that one answered your question. I was wondering the same thing. The solar panels would be radiating heat on a large scale \.

1. Bob

Weird, professional materials scientists aren’t just hanging around for more than a year just waiting to answer questions.

For surfaces, grass absorbs 75% of incident radiation. Compared to the estimate that solar panels absorb a total of 90%, that makes it look like panels could result in net heating over grassland. However, today’s panels often run above 20% efficiency, making the heat absorption 70%, 10% reflected, and 20% stored as electrical potential. For comparison, asphalt absorbs roughly 90%, concrete roughly 75%.

For all materials, the heat they absorb is effectively radiated away (or heat is exchanged with the atmosphere, which eventually radiates the heat itself). Most surfaces emit broadband radiation in the near to far infrared. Silicone (from PV panels) radiates more strongly in the near infrared and somewhat in the atmospheric window (the band of IR wavelengths that are mostly able to pass unabsorbed into space). So an additional portion of the heat radiation from panels is passed through the atmosphere, improving their performance over most other surfaces/materials. The reason they get hot is because the have somewhat low overall emissivity, meaning that while in direct sunlight, they are absorbing radiation faster than the can emit it, not because they are absorbing more than the grass around the panel..

Their performance can (and probably soon will be) improved by materials that radiate heat faster. Even a soda lime glass top plate could keep panels 10-20f cooler by higher overall emissivity, and with a large portion of their radiated heat falling within the atmospheric window. This passive heat radiative cooling work has mostly been picked up in the past 5 – 10 years, so hopefully we’ll see those changes that can result in much better performance than panels currently have, with a lot of heat radiated directly into space (something like 100 watts per square meter). That would result in their overall heat absorption being something akin to a light colored paint

2. A

Hubby thinks that they don’t make a big difference that way. A roof, or the ground, also absorbs some heat and reflects some back.

4. Miraj

what law of thermodynamics told that with increased heat comes decreased power output? 1st, 2nd, or 3nd?

sorry I’m still learning it