Quick Answer
Solar panels produce less energy during scorching summer days due to high temperatures causing a reduction in their efficiency. This phenomenon is known as thermal derating. As a result, solar panels typically operate at 90-95% of their maximum capacity in hot conditions.
Temperature Impact on Solar Panels
Solar panels are designed to operate within a specific temperature range, typically between -20°C and 40°C (−4°F and 104°F). When temperatures rise above 40°C (104°F), the efficiency of the solar panel decreases. For every 1°C (1.8°F) increase in temperature, the efficiency of a typical solar panel can decrease by 0.5-0.6%. This is because high temperatures cause the material’s resistance to increase, reducing the flow of electrical current.
Derating Factors and Losses
To account for the thermal derating, manufacturers often specify a derating factor, which is a percentage reduction in the panel’s maximum power output. For example, a solar panel with a maximum power output of 300W might have a derating factor of 0.85 for temperatures above 40°C (104°F), resulting in a maximum power output of 255W. This derating factor takes into account the losses due to high temperatures, as well as other factors such as panel shading, soiling, and electrical losses.
Mitigating Summer Heat Derating
To minimize the impact of summer heat derating, it’s essential to choose solar panels with high efficiency ratings and to ensure proper installation and maintenance. This includes using a suitable mounting system to ensure good airflow around the panels and regular cleaning to minimize soiling. Additionally, selecting panels with high temperature coefficients can help mitigate the effects of thermal derating.
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