French reactor squeeze pushes power past €300

The 20.4% figure that made the headlines was a snapshot, not the full picture. AFP calculated it from EDF reactor notices before 10:00 on 12 August, the moment when the largest share of France's nuclear fleet was marked unavailable for environmental reasons (Europe 1, France 24). Some of those reactors were still producing, just at reduced power. The real story for Malta, and for anyone exposed to Europe's wholesale power market, is what prices did when that missing French output met peak demand.

Day-ahead electricity prices, the price buyers agree today for power delivered tomorrow, rose 21.8% in France to €142.50/MWh and 22.8% in Germany to €138.50/MWh (Euronext/Reuters, Oilprice). By evening, as solar generation dropped and air-conditioning demand stayed high, same-day prices in both countries climbed above €300/MWh (The Edge).

13 reactors, two problems

Of France's 57 nuclear reactors, 13 were affected: eight fully stopped and five running below capacity (Euronews, Barron's).

The familiar problem was hot rivers. French nuclear plants use river or sea water to cool their systems, then return it warmer. Environmental rules limit the temperature of that returned water to protect fish and river ecosystems. When the Garonne reached 28°C, the Golfech plant had to scale back. At Chooz, near Belgium, low flow on the Meuse triggered a Franco-Belgian water-sharing agreement, and the reactor stopped entirely to preserve water for downstream users in both countries (EDF Chooz, Franceinfo). Similar limits hit plants on the Rhône.

The less expected problem was jellyfish. At Gravelines, France's largest nuclear site on the North Sea coast, a mass arrival blocked cooling-water intake pumps. EDF shut three units and reduced a fourth, pushing environmental unavailability above the previous record of 15.6%, set only two days earlier (EDF, Le Figaro).

Scarcity in France, higher bills next door

Europe's electricity markets are linked through daily auctions and interconnectors, the cables that move power between countries. Scarcity in France can therefore raise prices elsewhere. When cheap nuclear power drops out, more expensive gas-fired plants are called in. The last plant needed to meet demand usually sets the price for that hour, so gas can price the whole market even when most electricity is still coming from cheaper sources.

The pressure increased because German wind output fell to 4.7 GW, around 60% below the seasonal norm (Euronext/Reuters). Two of Europe's largest sources of low-cost electricity weakened at the same time. Then evening solar generation disappeared, exactly when households were still cooling homes.

The European Commission said on 11 August that the system remained stable, with interconnectors moving power towards tighter regions (European Commission). No country lost supply. But Malta knows the difference between security of supply and affordable supply: the lights can stay on while the bill becomes harder to absorb.

Dutch households on dynamic contracts, where the retail price follows wholesale prices hour by hour, felt the hit most directly (NL Times, Welingelichte Kringen). Italy, a major buyer of French power, saw available exports shrink during a similar June episode from around 10-12 GW to roughly 3 GW (DW). Romania's Cernavoda Unit 2 was already offline after Danube drought cut its cooling supply, tightening southeastern Europe separately.

The winners were gas plant owners and battery operators selling into those high prices. Their fuel costs, or the cost of stored electricity, did not rise in the same hour. The gap between what they paid and what they earned widened.

Small annual losses, expensive hours

EDF says climate constraints barely dent annual output. The historical record supports that claim: losses stayed below 1% of French nuclear production in almost every year from 2000 to 2022, reaching about 1.5% only in the extreme summer of 2003 (DW). The company plans to spend roughly €9 billion over 15 years adapting its fleet to rising temperatures (Le Monde).

Annual averages, however, hide where the cost lands. It falls on households and businesses buying electricity in the hours when several reactors cut output together. Annual nuclear losses can remain small while the market cost is large, because electricity prices move quickly when cheap supply disappears during peak demand. Whether EDF's adaptation spending reduces those expensive peak-hour losses, or mainly limits total energy lost across the year, is something RTE, France's grid operator, and market data from future heatwaves will have to show.