Heatwave cuts French nuclear output by 3.65GW
EDF has shut down three reactors to protect river ecosystems from hot water discharges, highlighting the growing vulnerability of Europe's power systems to extreme heat.
France's state-owned electricity producer EDF has taken 3.65 gigawatts of nuclear capacity offline as a severe heatwave raises river temperatures across the country. Three reactors—Golfech Unit 2, Bugey Unit 3 and Chooz Unit 2—were shut down on Sunday, removing roughly 6% of France's 61GW installed nuclear fleet from the grid. "Seven other nuclear reactors may be required to adapt their power output, which fluctuates throughout the day," said an EDF spokesperson.
The curtailments are driven by environmental regulations rather than reactor safety limits. "There is no nuclear safety risk. Reactors are capable of operating under high-temperature conditions. These limits are intended to protect aquatic flora and fauna," the spokesperson said. Nuclear plants draw river water for cooling and must restrict discharge temperatures to prevent ecological damage in waterways already warmed by the air.
For European power markets, the sudden removal of 6% of French baseload generation poses a tangible test of grid resilience. While EDF notes that production losses from heat and drought have averaged just 0.3% of annual nuclear generation since 2000, the concentrated impact of this heatwave prompted government action. The French economy ministry granted Bugey an exemption to discharge warmer water into the Rhône until 20 July specifically to ensure power grid security.
The current outages are the second heat-driven shutdowns since a record-breaking June heatwave, with over a third of France currently under the highest national weather alert. The three offline reactors are scheduled to return to service progressively between 19 and 25 July, though EDF warned these schedules will adjust according to changing forecasts.
A costly climate pivot
EDF is preparing for a future where such weather-driven disruptions become more frequent. The company said it disclosed in early 2026 that the estimated cost of a comprehensive climate adaptation plan is €8.7 billion over the next 15 years. The strategy covers the utility's nuclear fleet, hydropower assets and island energy systems.
To protect nuclear output during extreme heat, EDF is considering systems to cool discharged water before releasing it into the environment, a method already operating at the Civaux Nuclear Power Plant. The broader plan also includes measures to sustain hydropower generation during droughts and to strengthen island electricity networks against disruptive wind events.
