France's Nuclear Output to Drop 15% as Heatwave Peaks

France's nuclear power generation is set to fall by roughly 15% of total fleet capacity on Friday, as the fifth heatwave of the European summer forces reactor curtailments. Operator EDF data shows six reactors will be fully offline, with total reductions reaching 9.4 gigawatts across nine units at the peak.

The output loss is driven by environmental rules that limit how much warm water plants can discharge into rivers. With river temperatures elevated, reactors must reduce output to protect aquatic ecosystems. The shortfall is already rippling across borders, pushing Britain and Germany to rely more on coal and gas generation to compensate for reduced French nuclear exports.

Market impact was immediate. The French day-ahead power contract for Friday climbed 4.4% to €154.50 per megawatt hour, the highest level since June 23. Prices are typically subdued in August, a major holiday month when demand drops, making this spike notable.

Meteo-France forecasts Thursday as the peak of the current heatwave, with temperatures between 35°C and 40°C across most regions. Cooler Atlantic air is expected to bring relief to western areas on Friday, though the rest of the country will remain warm.

Despite these outages, France's nuclear output has improved year-on-year in June and July, thanks to a revised maintenance schedule. The Gravelines plant in the north, previously hit by jellyfish blockages, has also resumed operations. Nuclear power supplies about 70% of France's annual electricity.