France Cuts 6.4 GW of Nuclear Output as Heatwave Forces Reactor Stoppages
Repeated summer heat strips French nuclear supply during peak demand, pressuring power exports across Europe.
France's nuclear power generation was slashed by 6.4 GW on Monday (2026-07-13) after rising river temperatures forced EDF to halt three of the country's 57 reactors entirely and throttle output at others, according to OilPrice.com. The curtailed volume amounted to 14% of France's overall power demand that morning.5
France relies on nuclear for around 70% of its electricity and serves as Europe's largest net power exporter, which means reactor curtailments ripple outward quickly. When French supply drops, neighbouring markets absorb the gap — German power prices move, and reduced gas displacement in the French mix places incremental upward pressure on ICE Endex TTF front-month gas.5
The immediate trigger is river temperature. Inland nuclear plants use river water for cooling and must throttle or shut when discharge temperatures breach environmental limits. On Monday (2026-07-13), the Rhone and other rivers had warmed enough to trigger those restrictions. EDF had encountered the same constraints a month earlier, delaying a 1.1 GW capacity cut at its St Alban 2 reactor on the Rhone — originally planned for Wednesday (2026-06-24), pushed to Thursday (2026-06-25) — as heat hit around 3% of French nuclear capacity the day after the country recorded its hottest day on record, Montel reported.4
The pattern is not new, but it is worsening. France recorded that hottest day on record during a late-June heatwave that also forced EDF to temporarily shut two reactors as a precautionary environmental measure, according to reporting from late June (2026-06-25).6 Politico reported on Monday (2026-07-13) that a summer of fierce heatwaves has fuelled concerns about whether France's nuclear infrastructure can sustain output on what it described as the planet's fastest-warming continent.7
EDF has quantified the long-run exposure. In a June (2026-06-02) report, the utility told Montel that climate change could jeopardise almost 2%, or 8 TWh, of French power output by 2050, and said it was planning to adapt both its nuclear production and hydropower generation to cope. The specific upgrade timelines were not disclosed.2
EDF's own output targets make the stakes concrete. The company's half-year report set a 373 TWh nuclear output objective for France in 2025 — against 362 TWh the prior year — and flagged a resilience programme for the entire generation fleet alongside work to increase hydropower availability.3 Each unplanned heat curtailment erodes the headroom against that target.
Despite Monday (2026-07-13)'s cuts, France held onto its net exporter status. RTE data cited by OilPrice.com showed over 10 GW flowing to neighbouring countries that day. But that surplus is not a fixed buffer — it narrows each time the grid loses another block of nuclear capacity to heat restrictions.5
EDF is simultaneously pushing to grow electricity demand. In May, the utility told Montel that electrification was "imperative" for France following the energy shock triggered by the Iran war, announcing a plan to increase power demand by 5.5 TWh, or 1%, per year. New heat pumps and electric trucks alone could contribute 0.5 TWh annually.1
Growing load onto a fleet that loses output every summer when temperatures climb is a compounding exposure. The 5.5 TWh of annual demand growth EDF is targeting has to be supplied by something — and the current generation fleet is being trimmed by the same climatic conditions that make electrification attractive in the first place.1,5
French power front-month sentiment is tilted bullish, with no offsetting bearish signal in the current consensus. French power day-ahead was priced at €71.51/MWh as of Monday (2026-07-27) morning. The scenario that would invalidate the bullish read is a swift break in summer temperatures allowing sidelined capacity back online before peak cooling demand peaks — and there is no indication in the source material that such relief is imminent.
The figure to track is how much of France's 373 TWh nuclear output target for 2025 remains achievable if summer curtailments continue at the pace established since late June. Europe's power balance through August depends partly on how many more reactor-hours France loses to the Rhone.3,5