Extreme heat events across Europe in June and July 2026 impacted electricity generation across all major technology types, with increased demand straining power systems as temperatures exceeded 40 degrees Celsius in some regions.
Nuclear power facilities experienced significant disruptions, particularly those relying on river cooling systems. In France, where nuclear generates roughly 70 percent of electricity, three reactors shut down and seven others reduced output during the July heatwave, resulting in an approximately 9 percent decline in generation. Similar challenges affected nuclear plants in Romania, Hungary, and Switzerland as river water levels dropped and temperatures rose. Nuclear plants typically use river or sea water for cooling, and when water temperatures increase or availability decreases, their efficiency declines. While such impacts are generally temporary when caused by high water temperatures, drought conditions can create prolonged reductions in nuclear capacity. Across the globe between 2003 and 2022, heatwaves reduced annual nuclear generation by an average of 0.6 percent, though adaptation measures have improved outcomes significantly.
Gas power plants also faced capacity reductions during extreme heat, though this impact is sometimes downplayed in media coverage. Gas facilities experience reduced efficiency as ambient temperatures rise, with some systems losing up to 13 percent capacity at 40 degrees Celsius. The lower density of hot air also reduces the fuel-to-air mix in certain plant designs. Several countries including the UK and France saw gas capacity cuts during the 2026 heatwave, though the industry maintains sufficient reserve capacity to meet demand at premium prices.
Wind and solar generation showed mixed effects. Wind speeds typically decline during high-pressure systems that create heatwaves, with generation falling by 30 to 50 percent during extreme heat across much of Europe, northern Asia, and Australia. In the UK during June 2026, wind dropped to around 15 percent of the electricity mix from a typical 30 percent. However, solar generation often increases during heatwaves despite modest efficiency losses from heat, as extended clear conditions provide abundant sunlight. Solar set records across the European Union in June 2026, and the technology proved complementary to air conditioning demand patterns.
Battery storage systems emerged as increasingly important tools for managing heatwave impacts, though they face their own temperature-related challenges. More than 108 gigawatts of battery capacity was added globally in 2025 alone, helping to shift daytime solar generation to evening peaks when cooling demand remains high. Despite some performance degradation at elevated temperatures, battery systems with appropriate cooling mechanisms continue operating effectively and represent a key component of grid resilience during extreme heat events.
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