How solar saved the grid during Europe’s heatwave

Energy think tank Ember’s new report highlights the impact of extreme summer temperatures on the grid and the role record solar output played in maintaining grid stability. The report focuses on four countries; France, Spain, Italy and Hungary, analyZing the impact of June-July 2026 heatwaves and drought on power demand, generation and prices. According to Ember, during heatwaves beginning in late June, daily power demand increased by as much as 28% in Italy, 23% in Hungary, 14% in France, and 13% in Spain. This is compared to the week preceding the heatwaves (13-19 June), when temperatures were closer to normal seasonal averages. The high temperatures resulted in increased demand from air conditioning requirements, while simultaneously disrupting hydropower and nuclear output. Supply scarcity Europe, in this case, experienced record solar output together with the increase in temperatures. This, states Ember in the report, helped cover increased demand during daylight hours, with high prices and supply scarcity most pronounced in the evenings. Solar production was up to 17% higher on heatwave days compared to other days in June and July, which not only helped stabiliZe the grid, but also mitigate the disruptions caused to other generation sources. Specifically, European hydropower production was at its lowest level in at least a decade for May, June and July. Also, states the report, in Hungary and Romania, record low Danube water levels sharply reduced output from the countries’ only nuclear power stations, which typically provide 40% and 15% of their respective electricity generation. Ember suggests complete shutdowns may be necessary if water levels do not recover. These impacts on power generation sources have led to a dramatic rise of electricity prices, with early evening peak prices in some markets reaching their highest levels since the 2022 gas crisis. Dr Chris Rosslowe, senior energy analyst at Ember, commented on the findings: “Solar is already doing heavy lifting during heatwaves, but the real challenge starts after sundown.” System resilience Rosslowe points to battery storage as one the clearest paths to a more resilient power system in hot summer months. “As solar performs during heatwaves while other power sources struggle, storage can carry cheap electricity into the evening, when cooling demand is still high and the grid is most exposed to expensive thermal power.” The fact that increased solar generation could help limit price increases during daylight hours, but not in the early evenings, shows a lack of flexibility, says Ember. Flexibility can be sourced from battery storage, demand response or interconnectors between countries or regions. Ember points to battery storage as being well suited to answering the flexibility question, stating that “additional storage could shift low-cost solar power into the evening, better aligning supply with cooling demand and reducing reliance on expensive thermal generation.” Originally published in Factor This sister publication Enlit World.