French Nuclear Outages Fall to 10.6% as Cooler Weather Eases River Pressure
EDF data show French nuclear outages easing from a 12% fleet peak, as Triodos puts Europe's potential summer heat cost at $207.7 billion.
An August report from Dutch bank Triodos, published Friday (2026-08-21), estimated that Europe's summer of extreme heat could cost around $207.7 billion, roughly 1% of EU GDP. Widespread disruption to nuclear power plants was listed among the drivers. France, home to the continent's largest nuclear fleet, has accounted for some of the most acute disruption, and EDF data through Thursday (2026-08-20) suggested conditions were finally easing.4
Montel reported that French heat-related nuclear outages were set to fall to 10.6%, or 6.7 GW, of the country's installed capacity on Thursday (2026-08-20), driven by cooler, wetter weather that reduced pressure on river temperatures used to cool reactors. Outages were forecast to ease further to 6.8% of fleet capacity by Friday (2026-08-21), according to EDF data.3
The improvement came after a punishing stretch. On August 3 (2026-08-03), curtailments hit 7.6 GW — 12% of installed capacity, the highest point since the latest heatwave began the week of July 27 (2026-07-27) — EDF data showed. The following day (2026-08-04), cuts were projected to recede to 4.3 GW, or 7% of capacity.2
Recovery at individual sites gave more texture to the improving picture. A 1,310 MW heat-related outage at Golfech 2 ended at 07:30 CET on Thursday (2026-08-20), 3.5 hours earlier than previously expected. Heat-related restrictions at Bugey 3, a 910 MW unit, were also in the process of easing, Montel reported citing EDF data.3
The summer's curtailment pattern reflects a persistent vulnerability in the French fleet. Reactors depend on river water for cooling; when water temperatures breach environmental thresholds, stations must reduce output to prevent further warming of waterways. As multiple heatwaves moved through France from late June onward, that constraint triggered output cuts at Golfech, Bugey, and other river-sited stations.3,2
The disruption had been building since early July. On Monday (2026-07-13), EDF cut 6.4 GW, equivalent to 14% of France's total power demand at the time, amid a prolonged heatwave that pushed river temperatures beyond acceptable cooling limits, data from oilprice.com showed. Even so, France remained a net exporter: RTE data showed over 10 GW flowing to neighboring countries on that morning.1
That export capacity illustrates the reach of the French nuclear fleet into European power balances. Nuclear generation accounts for about 70% of France's electricity mix; when the fleet operates at full capacity, France exports power to Germany, Spain, Italy and the UK. When heat forces curtailments, neighboring power balances tighten and the call on gas-fired generation rises across Northwestern Europe.1
The Triodos figure covers economic losses from Europe's heat broadly — agriculture, labor productivity, and infrastructure alongside energy — and is framed as a potential estimate rather than a confirmed accounting. But for power market participants, France's share of European baseload supply makes its fleet the most direct transmission point from summer temperatures to regional availability.4
With cooler weather providing some cover through late August, the pace of unit restarts will shape near-term French output. Progress at Bugey 3 and any revisions to EDF's rolling outage schedule will be the signal to track as European demand begins its seasonal build toward September.3