How hot do solar panels get? PV temperature explained

Solar panels are often exposed to high 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.

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.

Most solar panels are composed of silicon photovoltaic (PV) cells, 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, 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, the level of direct sunlight, and roof material.

Homeowners considering solar often wonder, "Can solar panels overheat?" Like with any other electronic equipment, solar panel performance declines as they get hot – the laws of thermodynamics tell us that with increased heat comes decreased power output, which applies to solar panels. Thus, warmer temperatures will always mean less work 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 by the temperature coefficient, expressed as a percentage per degree Celsius. Testing solar panels for power output at 25 °C is standard practice. So, if a panel is rated to have a temperature coefficient of -0.50% per °C, that panel's output power will decrease by half 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 solar panels have 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 decreases to 16.3 percent.

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.

Thin film panels are a recent market innovation with a temperature coefficient rating between -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 generally are less efficient than their crystalline PV counterparts.

An important note to remember about temperature coefficients is that if a panel operates in temperatures lower than 25 °C, the temperature coefficient will 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 means you don't have to live in a warm climate to benefit from solar power. This efficiency gain in cold weather helps offset losses during the summer months, especially for homeowners living in regions with distinct winter/summer weather cycles.

Conversely, if you live in a warm and sunny climate 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.

Solar installers customize their system designs to meet each property's specific needs, including 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 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, add a note to your profile when registering.