What is Temperature Coefficient?
A measure of how much a solar panel's output decreases as temperature rises above 25°C.
Quick Answer
The UK's cool climate is actually an advantage for solar panels. Panel surface temperatures in the UK rarely exceed 40°C, compared to 60°C+ in hot countries. This means UK panels operate closer to their rated efficiency. On a clear summer day in the UK, panels might lose only 3–5% to heat, compared to 10–15% in Spain or Italy.
Fact-checked by John Rooney, Solar Energy Editor. Editorial policy
Temperature Coefficient Explained
The temperature coefficient of a solar panel describes the rate at which its power output changes with temperature. It is expressed as a percentage change per degree Celsius (e.g. -0.35%/°C). Since panels are rated at 25°C (STC), every degree above 25°C reduces output by the temperature coefficient amount. For example, at 35°C, a panel with -0.35%/°C coefficient loses 3.5% of its rated output. Lower (less negative) coefficients are better.
How Does Temperature Coefficient Work in the UK?
The UK's cool climate is actually an advantage for solar panels. Panel surface temperatures in the UK rarely exceed 40°C, compared to 60°C+ in hot countries. This means UK panels operate closer to their rated efficiency. On a clear summer day in the UK, panels might lose only 3–5% to heat, compared to 10–15% in Spain or Italy.
Frequently Asked Questions
Do solar panels work better in cold weather?
Panels are more efficient in cold temperatures, yes. But cold weather usually means less sunlight. The UK's moderate temperatures give a good balance of efficiency and light levels.
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John Rooney is the founder of Solar Info and has been covering the UK solar energy market since 2023. He fact-checks all content against official MCS and Ofgem data and maintains relationships with MCS-certified installers across the UK.