How does hot weather affect energy generation?
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When heatwaves hit, solar generation rockets - generating green electricity by the bucketload.
In contrast, wind power tends to fall, which many anti-green energy propagandists point to with glee. But what we don’t hear about is the vulnerability of conventional fossil and nuclear generation to our ‘new normal’ summers.
During one of the hottest days ever recorded in June, with temperatures reaching around 35°C, UK wholesale electricity prices surged up to £800 per megawatt-hour – that’s around six times higher than normal. A significant factor behind the spike was the reduced performance of gas-fired power stations when it gets hot.
Gas power stations lose up to 1.5 per cent of their efficiency for every degree of temperature rise. In the recent heatwave, Britain experienced temperatures so high that the efficiency of gas power stations dropped by a staggering 22%.
The UK has over 30GW of gas burning power stations, typically operating at around 48 per cent efficiency during the summer. A 22 per cent reduction equates to a loss of over 7GW of effective generating capacity.
Extreme weather is also affecting other forms of 'conventional’ power generation. In Europe, at least six nuclear reactors had to be turned off or curtailed during the heatwave. And low river levels have disrupted coal-fired generation in Germany by limiting the amount of coal that can be transported by barge along the Rhine.
Our founder, Dale Vince, says: “Climate change isn't just increasing demand for electricity through hotter summers - it's also making fossil fuel and nuclear power less reliable than energy from the wind and the sun.”
How do heatwaves affect solar panels?
Solar generation depends on light rather than heat - solar panels turn sunlight directly into power through the photoelectric effect. Direct sunlight yields the highest energy output, but cloudy days also provide consistent power generation.
In fact, Britain receives enough sunlight throughout the year to make solar power a core pillar in the national energy mix, with even cloudy days producing a consistent flow of renewable electricity.
While the extreme heat can have a small impact on the efficiency of solar panels, they are far less affected than gas-fired power stations. Solar efficiency drops by roughly 0.5 per cent for every 1°C rise above their rated operating temperature of 25°C, around a third of the efficiency loss seen in gas-fired generation.
It’s also important to remember that heatwaves come with bright sunshine, long days and clear skies we mentioned above, so while efficiency could drop, overall generation output skyrockets as we can see from Europe hitting record-breaking solar generation totals in June 2025’s heatwave. That’s a stark contrast to fossil fuel generation, which becomes less efficient as temperatures rise.
Do windmills work in heatwaves?
Windmills work well in the kinds of temperatures we experience in Britain, even in the worst heatwaves. Their efficiency is most affected around 40-44°C and even then it only makes a 1 per cent difference.
Wind energy output usually drops because heatwaves are caused by persistent high-pressure atmospheric systems that create extended periods of calm conditions. So, essentially less wind.
While gas-fired power stations become less efficient as temperatures rise and nuclear plants can be forced to reduce output, wind turbines continue to operate normally. They just have less wind to capture.
Even with generally less wind, it’s not a case of all or nothing – in heatwaves, including July 2026, there are often periods of breezy weather and windmills only need a light wind to start generating.
Even with climate change, this is what we expect from the seasons in Britain. Our summers bring more sun and our winters bring more wind, which is why it makes perfect sense to run a national solar and wind strategy, backed by grid scale energy storage. It just makes sense to use renewable energy throughout the year, especially with the growing vulnerability of fossil fuel and nuclear generation to extreme heat.
Is hot weather a problem for the National Grid?
The high temperatures we experience in heatwaves create physical problems for the grid while simultaneously driving up consumer demand.
The electrical grid is the system that links green and fossil energy generators to our homes and businesses. Powerlines heat up as a result of both energy transmission and ambient temperatures - as the temperature increases, the metal conductors in overhead lines expand so they sag closer to the ground.
This means that grid operators must sometimes restrict the total power allowed through the system to maintain safe ground clearances.
At the same time, heatwaves create spikes in power consumption. While cold weather energy surges are driven by heating and lighting, heatwaves see millions of air conditioning units, cooling fans and refrigeration systems run simultaneously. This places huge demand on the grid at a time when operators may be trying to limit the power.
Wildfires are another risk for the grid, damaging powerlines and other infrastructure with the potential to cause long-lasting power cuts over wide areas. Sometimes an outage can be caused simply by smoke and ash in the air providing a path for electricity from overhead cables to strike the ground like lightning and trip safety systems.
How can we build a heatwave-resistant green energy system?
Extreme temperatures introduce challenges for every form of power generation. While solar panels lose a little efficiency at high temperatures and wind power can slow down in the summer, green energy has far fewer problems than fossil or nuclear plants.
The key to protecting our energy system lies in increasing green energy sources and grid scale storage, while accelerating the modernisation of the grid at the same time to cope with our changing climate.
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