Record French nuclear shortfall as heat, jellyfish hit reactors

A prolonged summer heatwave is straining power grids across southern and central Europe, forcing nuclear plant shutdowns, depleting hydroelectric reserves, and driving electricity prices sharply higher in Italy, Hungary, and France simultaneously.

Nuclear Output Slashed Across the Continent

France recorded a more than 20% shortfall in nuclear generating capacity on August 12, a record deficit caused by drought, extreme heat, and a jellyfish invasion that clogged cooling pumps at the Gravelines plant in northern France, according to Euronews. In total, 13 of EDF's 57 reactors were affected — eight fully shut down and five operating at reduced power. Reuters reported on August 11 that French nuclear output was expected to be limited by 7.3 gigawatts at the midday peak, about 12% of the entire fleet.reuters+1

Hungary shut down its sole nuclear power plant, Paks, on August 3 after Danube River levels fell to record lows, depriving the facility of cooling water. The plant supplies nearly half of Hungary's electricity. By August 10, rising water levels allowed one turbine to restart, bringing output to 339 MW — far below the plant's normal 2,000 MW capacity. Prime Minister Péter Magyar said it could take more than a month for Paks to return to full operation.balkangreenenergynews+1

Prices Surge as Supply Tightens

Italy's wholesale power prices climbed to their highest level since winter 2022 as hot, dry weather forced greater reliance on costly natural gas generation, Bloomberg reported on August 4. According to Ember data, Italy's average day-ahead price reached €156.77/MWh in July, up 18.5% month-on-month, while France's jumped 45.8% to €96.61/MWh. In southeast Europe, spot prices briefly exceeded €700/MWh during the first week of August.linkedin+2

Reuters reported on August 11 that a fifth summer heatwave lifted European spot power prices by more than 20% in a single session, with further curtailments expected. Italy placed all major cities on red alert as temperatures exceeded 40°C.france24+1

Complex Outlook for Energy Markets

The crisis has exposed the vulnerability of Europe's power infrastructure to simultaneous heat-driven disruptions. While southern markets face tight supply, Nordic power prices have fallen on forecasts of wetter weather boosting hydroelectric reservoirs. German spot prices also softened on higher wind generation, underscoring sharp regional divergences across the continent.marketscale+1

Reuters reported that Hungary had begun restarting capacity at Paks as Danube levels recovered, but analysts warn that further heatwaves could trigger renewed shutdowns. "The heatwave is expected to be at its highest from Wednesday to Friday in France, so I'd expect significant shutdowns," Kpler analyst Alessandro Armenia told Reuters.reuters+1