How does Temperature Affect Electricity Generated by Solar PV Panels?

How much variation does temperature cause for generating electricity from Solar PV Panels?

With one of the hottest days in the UK so far this year it is interesting to compare the output for a hot sunny day with a cooler sunny day earlier in the year.

The best generating day in April was 19kWh for a clear sunny day with temperature of 12C. Yesterday generated 17kWh for a clear sunny day with a temperature of 27C despite the longer generating time with the lengthening days.

Solar panel output with different temperatures.

As you can see the output was for longer on the blue day (24 May) but the peak was lower than on the green day (2 April) as the temperature was far lower. The equation is the temperature coefficient which for our panels is 0.5% meaning output drops by 0.5% per degree over 25C. So for panels at 35C which is 10 degrees higher the output would be 5% lower.

As another comparison the maximum peak generation was around 2.3kW yesterday but for cooler days this has been as high as 2.5kW and for cloudy days with sunny spells it has peaked as high as 3kW showing the effect that temperature has on solar power generation.

One company was selling a hybrid solar panel that included water heating as well as electricity generation. As a method for cooling the solar panels to improve their efficiency it seems like an effective method based on this data as the water will extract the heat that can then be used for hot water in the house.

Solar panel generation in high temperatures