Solar output in European countries boosted by up to 17% on hot days, helping to meet higher power demand from heatwaves

Brussels, 13 August 2026 – New analysis from Ember reveals that solar output in European countries rose by up to 17% on heatwave days in June and July. This helped power the grid as electricity demand jumped by as much as a quarter on hot days.

The analysis examines the impact of heatwaves on some of the power systems mostly affected. During the late-June and July heatwaves, daily electricity demand rose by up to 28% in Italy, 23% in Hungary, 14% in France and 13% in Spain compared with pre-heatwave days.

As heatwave-driven demand increased, solar was the only major power source to perform better than usual. Compared with other days in June and July, average daily solar generation during the heatwaves was 17% higher in France and Hungary, 5% higher in Spain and the same in Italy.

“The surge in solar output helped stabilise grids at a time when other power sources were struggling to deliver,” says Chris Rosslowe, senior energy analyst at Ember.

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Extreme heat and drought lead to supply disruption

Extreme heat and drought squeezed nuclear, gas and coal power supply across Europe during this summer’s heatwaves. Nuclear output was curtailed in France, Hungary, Romania and Switzerland. Five UK gas plants cut 2.5 GW during June’s heat and low water levels on the Po river threatened Italy’s gas generation. Drought-related cooling constraints forced coal plants in Poland and Serbia to reduce output.

Hydropower also struggled. In July, seven of the EU’s eight largest top producers, which together account for more than 90% of EU hydro generation, recorded output below their five-year averages.

“Solar is already doing heavy lifting during heatwaves, but the real challenge starts after sundown. In the evening, when cooling demand is still high, the grid is most exposed to expensive gas-fired power,” says Chris Rosslowe.

Heatwave impacts lead to spiking prices

During the late-June and early-July heatwaves, average daily prices were 119% higher in Hungary, 44% in France, 13% in Italy and 7% in Spain than on comparable days in the preceding weeks. In several markets, power prices also spiked in the early evening, reaching some of their highest levels in years.

While solar saves the day, battery storage can save the evening. Together, they are one of the clearest ways to make Europe’s power system more resilient in hotter summers. As solar output rises during heatwaves and other power sources struggle, storage can carry that cheap electricity into the evening

Chris Rosslowe
‍Senior energy analyst, Ember

About Ember

Ember is an independent energy think tank that aims to accelerate the clean energy transition with data and policy. It creates targeted data insights to advance policies that urgently shift the world to a clean, electrified energy future.

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