Heatwave means loss in solar panel efficiency – experts say

Renewable energy specialists Dwellow, based in Didcot in Oxfordshire, have warned that solar panels lose efficiency in extreme heat, despite the increase in sunlight.

The warning comes as temperatures in parts of the UK are forecast to reach 38C.

Ian McLaren, founder of Dwellow, said: “Solar panels generate electricity from sunlight, not heat.

“There’s a common misconception that hotter weather automatically means better solar performance, but in reality, excessive heat can reduce efficiency.”

Most solar panels are tested under Standard Test Conditions of around 25C.

For every degree above this, panels typically lose between 0.3 and 0.5 per cent efficiency.

During a heatwave, rooftop panels can reach 60C or more, cutting output by 10 to 20 per cent.

Adam Raw, co-founder of Dwellow, said: “In-roof systems sit flush within the roof structure, which looks fantastic aesthetically, but they generally have less airflow behind the panels compared to on-roof systems.

“That reduced ventilation means heat becomes trapped more easily, causing the panels to run hotter.”

Despite the loss in efficiency, Dwellow says that longer daylight hours and clear skies still make heatwaves some of the most productive periods for solar energy overall.