Forecasters Warn France of Fifth Heatwave and Fresh EDF Nuclear Cuts
Experts told Montel on July 28 that an imminent heatwave could force EDF to cut output again, the fifth such disruption to France's nuclear fleet this summer.
Forecasters told Montel on Tuesday (2026-07-28) that EDF is likely to be forced into fresh nuclear output cuts, as an imminent heatwave was expected to last at least a week and push local temperatures to 40C. The alert came a fortnight after the mid-July event that stripped 6.4 GW from France's nuclear fleet.8
Nuclear power accounts for around 70% of France's electricity generation. When summer heat raises river temperatures enough to restrict cooling water, EDF must throttle or shut reactors to comply with thermal discharge limits. This summer has tested that constraint repeatedly.5
The scale of the mid-July episode shows how fast conditions deteriorate. On Monday (2026-07-13), nuclear output fell by 6.4 GW, equal to 14% of France's total power demand that morning, as EDF stopped three of the country's 57 reactors outright and curtailed production at several others, OilPrice.com reported.5,7
But the season's disruptions began six weeks before that. EDF shut two reactors on a precautionary basis on Thursday (2026-06-25) when river temperatures climbed during a record-breaking heatwave. Around 6.2 GW of capacity, 9.8% of France's total nuclear fleet, was offline at that point, Montel reported.6,2
By early July (2026-07-08), heat-related curtailments had reached 4.6% of France's nuclear output, according to Montel, before climbing to the 6.4 GW mid-month peak.4,5
The summer has gone against early-season forecasts. In May (2026-05-21), meteorological experts told Montel that France appeared set to experience frequent bouts of cooling rainfall and that the risk of nuclear disruption looked limited. June, they said, was likely to be the sunniest and warmest month before conditions eased. Instead, disruptions continued to mount through late July.1
One consistent feature of the season has been France's ability to maintain a net export position despite the cuts. RTE data showed the country exporting more than 10 GW to neighbouring countries on Monday (2026-07-13), even with the mid-July curtailments in effect.5
Yet demand across the continent was elevated at the same time. Fintan Devenney, senior energy analyst at Montel, said power demand was running high across Europe during the heatwave period, "driven in part by increased cooling load," narrowing the cushion France's export surplus provides to regional price stability.3
German power was trading at €131.16 per megawatt-hour as of Friday (2026-08-07), and ICE Endex TTF front-month gas held at €55.74 per megawatt-hour as of Friday (2026-08-07). Sustained French nuclear curtailments lift domestic power prices, which pulls German baseload higher and adds incremental support to European gas as gas-fired generation absorbs marginal demand.5
Politico reported on Monday (2026-07-13) that the sequence of heatwaves is feeding wider concern about whether France's nuclear infrastructure, designed for a cooler climate, can sustain reliable output through summers on what the publication called the planet's fastest-warming continent. EDF's operating margins on cooling water have narrowed each season.7
A meteorologist quoted by Montel on Thursday (2026-06-25) warned that a fresh heatwave could "quickly recreate critical" conditions for some reactors. That warning was issued again on Tuesday (2026-07-28) — in what would mark France's fifth heatwave of the season. How long the new wave holds temperatures above the cooling threshold at individual plants is the variable traders will need to track through August.2,8