Even nuclear power plants are affected by the heat.

Nuclear power plants in Croatia and France have been affected by heatwaves, leading to reduced electricity production. In Croatia, the Krško nuclear power plant has begun gradually reducing its reactor output due to low water levels and high temperatures in the Sava River. Operators described this measure as temporary, necessary to comply with ecological regulations that limit both the average temperature of the river and additional heating caused by the plant. Water from the river is used in the third cooling circuit to remove excess heat from condensers, which cannot be converted into electrical energy. The reduction in production is planned to bring capacity down to 80 percent, with further limitations possible if needed. This marks the first time since 2003 that the plant has operated at reduced capacity. At that time, the reduction lasted over three months, while a complete shutdown would typically last around seven days. Full operational capacity will resume once river flow and water temperature improve. Currently, the Krško plant supplies nearly 60 percent of daily electricity production in Slovenia. France plays a crucial role in the European electricity supply. No other European country relies so heavily on nuclear energy for its power grid. If French nuclear reactors reduce output, the country could send less electricity to neighboring states or even become a net importer. While annual reductions in production due to heatwaves appear contradictory, they are generally minimal. According to reports from the State Audit Office, annual losses caused by high water temperatures and low river levels have averaged below one percent of total nuclear production. Even during the extreme summer of 2003, losses were only around 1.5 percent. However, annual data masks short-term fluctuations. During the summer of 2003, French nuclear plants temporarily reduced output by more than six gigawatts. Similar reductions occurred during recent heatwaves in June and July 2026, with maximum available power temporarily cut by eight to nine gigawatts, about one-fifth of the usual summer capacity. Yet, these reductions do not necessarily mean that eight gigawatts of electricity were actually missing each day. Some reactors might not operate at full capacity due to lower demand, increased solar generation, or network congestion. According to grid operators, France maintained sufficient reserves and remained an exporter of electricity even during the heatwave of 2026. Heatwaves increase electricity consumption due to higher air conditioning usage. With this year’s heat affecting large parts of Europe, available reserves in foreign countries have also declined. Nuclear plants suffer from low river levels because they must discharge relatively large amounts of waste heat. Only about one-third of the heat produced in reactors is converted into electricity, while the rest is released through cooling systems, often into rivers or the sea. When rivers have low water levels, the discharged waste heat spreads over a smaller volume of water, making it harder to maintain safe operating conditions. This situation raises concerns about environmental impacts and operational constraints. As temperatures continue to rise, the challenge of balancing energy production with ecological requirements becomes increasingly complex. The interplay between climate change, energy demand, and regulatory frameworks will shape the future of nuclear power in Europe.