EDF Raises French Nuclear Curtailments to 10.8% as 42C Heatwave Tightens River Cooling
EDF's planned 6.8 GW cut for July 30 marked the summer's deepest heat-related curtailment and tested the limits of France's net exporter status.
EDF announced on Wednesday (2026-07-29) that heat-related output cuts to France's nuclear fleet would climb to 6.8 GW the following day (2026-07-30), or 10.8% of total installed capacity, as temperatures threatened to reach 42C and river cooling water approached permissible limits, Montel reported.4
The step-up was considerable. On July 29 itself, EDF was already running with about 6% of capacity curtailed. By Thursday (2026-07-30), the company planned to take 1 GW offline at St Alban 1, a 1.3 GW unit on the Rhone River in southeastern France, for the entire day, with a further 1 GW reduction at sister reactor St Alban 2 scheduled between 12:30 and 17:45 CET.4
Nuclear power provides roughly 70% of France's electricity. A curtailment of that scale does not automatically tip France from net exporter to net importer, but the margin narrows quickly. On Monday (2026-07-13), when EDF was running 6.4 GW of restrictions, equivalent to 14% of France's overall power demand that morning per OilPrice.com, RTE data showed France still exporting more than 10 GW to neighboring countries.2
The 6.8 GW projection for July 30 exceeded the July 13 peak. French reactors draw cooling water from rivers including the Rhone and Garonne; operators are legally prohibited from discharging water that exceeds temperature thresholds back into those waterways, forcing output reductions whenever ambient heat drives river temperatures high enough.4,2
The summer's restrictions had been building since early July. On Wednesday (2026-07-08), EDF imposed 3 GW of cuts from noon CET, equal to 4.6% of installed capacity, after disconnecting the 1.3 GW Golfech 2 unit on the Garonne River in southwestern France, Montel reported. Those restrictions began at 1.6 GW at 09:00 CET before reaching the 3 GW ceiling three hours later.1
France's heat-induced nuclear reductions had started even earlier. In late June (2026-06-25), EDF temporarily shut two reactors as a precautionary environmental measure amid a heatwave that Reuters described as record-breaking and already deadly.3
The pattern from late June through late July is one of extended partial operation rather than brief episodic cuts. The shift from 3 GW of restrictions on July 8 to 6.8 GW projected for July 30 — more than doubling in three weeks — reflects both the severity of this summer's heat and the thermal inertia of rivers: once water temperatures climb, they take time to fall back below operating thresholds even after daytime peaks ease.1,4
For European power traders, French generation shortfalls that cannot be covered by imports tend to shift demand toward gas-fired backup capacity. ICE Endex TTF front-month gas closed the week at €59.05/MWh. The degree to which the late-July curtailments tightened continental gas balances will emerge as settlement data for the period becomes available.4
River temperatures in early August are the variable to monitor. If the 42C forecast for Thursday (2026-07-30) was met — and the summer's record since late June offers little reason to doubt the forecasters — EDF could carry material heat-related restrictions into the first week of August, prolonging a season of heat-forced curtailments that dates to a record-breaking heatwave at the end of June.4,3