How Temperature Influences Solar Panel Efficiency
The amount of power generated by a solar panel depends primarily on two factors:
- The amount of sunlight hitting the panel.
- The temperature of the panel itself.
Solar panels have a negative temperature coefficient, meaning that as temperatures rise, their efficiency decreases. Conversely, they perform better in cooler conditions. As a result, solar systems may generate less peak power on hot summer days than on bright but cooler spring days.
Most solar panels have a temperature coefficient of about -0.35% per degree Celsius. This means that for every 3°C increase, power output decreases by roughly 1%. For example, if the panel temperature is 20°C on one sunny day but 44°C on another day with the same sunlight conditions, the efficiency on the hotter day will be about 8% lower due to the 24°C difference.
Energy output of a solar panel system on the same day of the year (April 20) in two consecutive years (2013 and 2014). In 2014 (left), the maximum temperature was 20.7°C, while in 2013 (right), it was 12.2°C. The temperature difference resulted in a noticeable variation in peak power output.
How Hot Do Solar Panels Get?
Because solar panels absorb sunlight, they can reach much higher temperatures than the surrounding air. In direct sunlight, a panel’s temperature can increase by 20 to 30°C above the air temperature. This means that on a 25°C summer day, solar panels can heat up to 50°C or more.
To minimize power loss due to heat, it helps to allow for some air circulation around the panels. Solar panels installed with a gap between them and the roof benefit from improved airflow, which helps them stay cooler and maintain higher efficiency. On flat roofs, mounting systems naturally create space for ventilation, reducing heat buildup.
Are Some Solar Panels More Heat-Resistant than Others?
Yes, different types of solar panels react differently to temperature increases. Some models are more sensitive to heat than others. The table below shows the temperature coefficient of various solar panel brands:
Brand & Model | Temperature Coefficient (Pmax) |
Trina Solar 265 Wp | -0.41 %/°C |
ET-Solar 245 Wp Poly | -0.44 %/°C |
Hanwha Q.Cells Q-Peak 275Wp | -0.40 %/°C |
SunPower E-Series (327 Wp) | -0.35 %/°C |
SunPower X-Series (345-360 Wp) | -0.30 %/°C |
SunPower Max3 (370-400 Wp) | -0.27 %/°C |
Let’s compare ET Solar 245 Wp (-0.44%/°C) and SunPower Max3-400 (-0.27%/°C). If the panel temperature rises from 20°C to 44°C, then:
- ET Solar panel loses 11% efficiency due to heat.
- SunPower Max3 loses only 6% efficiency, meaning a 5% difference in performance.
Over the course of a year, choosing a panel with better heat resistance can result in significantly higher energy production.
Is It Worth Actively Cooling Solar Panels?
In most cases, allowing natural ventilation under the panels is enough to keep temperatures manageable. Some manufacturers have experimented with water-cooling systems, but the extra costs and complexity often outweigh the small efficiency gains.
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