French Day-Ahead Power Extends 3.5-Year High Through Late September
French baseload day-ahead prices are on track to close September at a 3.5-year high, sustained by summer nuclear constraints and persistent cooling demand.
French day-ahead power prices are on track to close September at a 3.5-year high, Montel reported on Thursday (2026-09-24), extending a rally built through successive heatwaves and recurring nuclear output constraints across the summer.6
The week of September 7 (2026-09-07) set the monthly peak, with the French baseload day-ahead contract averaging EUR 151.26/MWh — the highest weekly average in three and a half years, according to Montel. At that point, Montel flagged a potential 6% price decline for the following week (2026-09-14) as nuclear generation was expected to recover.5
That recovery was not enough to break the monthly high. German day-ahead power stood at EUR 159.77/MWh on Thursday (2026-09-24), reflecting sustained tightness across the European interconnected grid rather than an isolated French event.5,6
Nuclear availability drives the French price story. EDF data showed the country's nuclear fleet cut by 7.3 GW on Wednesday (2026-08-05), equal to 12% of total installed capacity, as high river temperatures limited cooling water available to reactors. Nuclear accounts for about 70% of France's electricity mix. Even partial fleet outages shift the country from net exporter to price-taker on the broader European grid, spreading pressure to Germany and beyond.4
That August cut sent day-ahead prices up as much as 21.8%, reaching 142.5 euros/MWh on Tuesday (2026-08-11), per LSEG data cited by Reuters. France had already seen 6.4 GW of nuclear capacity removed in mid-July (2026-07) during a separate prolonged heatwave that drove river temperatures beyond the thresholds needed for reactor cooling, EDF data showed.4
The pattern established itself earlier in the summer. The French day-ahead contract for delivery on Tuesday (2026-06-16) settled at EUR 136.12/MWh, Montel reported, as a June heatwave pushed air-conditioning demand higher while threatening nuclear availability. Alexis Gleron, analyst at Augmented Energy, attributed the buoyant prices mainly to "increased use of air-conditioning" as temperatures spiked across the country.3
The cumulative effect has been a year of stepped price increases. Benchmark power contracts in France and Germany have both doubled since January, according to Reuters data cited by CNBC.2
ICE Endex TTF front-month gas traded at EUR 72.30/MWh on Thursday (2026-09-24). With TTF near that level, gas-fired generation remains expensive, meaning any nuclear shortfall is difficult to cover without pushing day-ahead power sharply higher. Both fuel inputs sit elevated, leaving little headroom to absorb further nuclear losses.2
The structural answer to France's nuclear vulnerability is years away. The European Commission on Tuesday (2026-05-19) launched a formal investigation into France's plan to subsidise the construction of six new nuclear reactors at an estimated EUR 73bn, with a combined capacity of 10 GW. The probe adds uncertainty to construction timelines, and even cleared projects face commissioning schedules measured in decades rather than years.1
EDF's forward nuclear availability data for October will be the first concrete test of whether reduced river-cooling constraints in autumn translate into meaningful output recovery. Montel projected a 6% price retreat for the week of September 14 (2026-09-14) as the nuclear fleet came back online; September extended the 3.5-year high regardless. If nuclear output remains below par through October, the winter forward curve faces another upward revision.5,6