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 typically located on the roof, which means they’re exposed to the elements. When the sun is shining down on them in the summer, they can be very hot to the touch.
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 solar panel efficiency changes in hot conditions
Efficiency at 30 °C (86 °F)
Efficiency at 35 °C (95 °F)
|Hanwha Q CELLS||-0.39||18.3%||18.23%||18.15%|
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 between -0.45 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 and Panasonic 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.