France and Romania Lose Nuclear Capacity as Drought Bites Across Central Europe
A fifth heatwave in weeks pushed French day-ahead power up 21.8% on Tuesday while Romania shut its last operating reactor as the Danube hit a 90-year low.
France's day-ahead power prices surged as much as 21.8% to 142.5 euros per megawatt-hour on Tuesday (2026-08-11) morning, per LSEG data cited by Reuters, as EDF warned that nuclear generation would be cut by 7.3 gigawatts — equivalent to 12% of the country's total nuclear capacity — at the mid-day peak on Wednesday (2026-08-12).6
The driver is familiar but the scale keeps growing. France generates roughly 70% of its electricity from nuclear power, so any constraint on reactor output transmits almost immediately into day-ahead prices. The current heatwave, at least the fifth intense heat event to grip France this summer, is driving river temperatures above the thresholds that permit normal cooling water discharge, forcing EDF to throttle output or halt reactors entirely.6
The same drought conditions are carving through central Europe with comparable effect. Romania's state nuclear operator Nuclearelectrica began shutting its only remaining operating reactor on Thursday (2026-08-13) after the Danube dropped to its lowest level in 90 years, according to reporting on the closure. That leaves Romania's nuclear fleet entirely offline, adding to the regional generation deficit arriving at a point when summer demand is still elevated.7
France's nuclear losses this summer have compounded week by week. In mid-July, EDF was forced to stop three reactors and reduce output at others when temperatures hit extreme levels, according to Politico, which cited Monday (2026-07-13) as the trigger date for those outages. In the middle of that same month, total generation losses reached 6.4 gigawatts, per EDF data cited in subsequent reporting — slightly below the 7.3 gigawatts now being flagged for the August heatwave, though both figures carry operational uncertainty depending on river temperature trajectories.5,6
The river-cooling mechanism binds the nuclear losses together across borders. Hungarian environmental law, for instance, sets a discharge temperature ceiling of 30°C within 500 metres of a plant's warm-water channel, with only narrow ministerial exemptions available, according to Techtimes. The Danube serves as the shared cooling artery for multiple central European plants; as it falls and warms simultaneously, the legal and physical constraints on reactor operation tighten in parallel across Romania, Hungary, and Austria's surrounding interconnected grid.8
The progression through the summer illustrates how quickly the situation escalated. As early as June (2026-06-15), Montel reported that French short-to-medium-term power prices surged amid forecasts for a week-long heatwave, with analysts warning that cooling demand and potential nuclear outages were the driving force. By late June, EDF had already shuttered two reactors as a precautionary environmental measure during what it described as a record-breaking heatwave.2,4
By July, Montel flagged a second major heatwave episode with France again identified as the epicentre, with forecasters warning of record-breaking temperatures. The cumulative effect on the nuclear fleet has been to compress the available capacity buffer heading into each successive heat event, meaning the market's reaction to each subsequent wave has had less spare generation to cushion against.3
The contrast with conditions only weeks earlier is stark. In mid-May, German, French, and Hungarian power prices briefly touched less than minus 400 euros per megawatt-hour intraday, per Montel, as a surge in renewable output combined with weak demand pushed markets to record negative territory on Sunday (2026-05-17). That episode highlighted the structural volatility in European power: the same markets that printed minus 500 euros in spring are now clearing at prices that reflect genuine supply strain.1
French power day-ahead settled at 130.21 euros per megawatt-hour as of the August 16 close, while Austrian day-ahead came in at 125.91 euros per megawatt-hour — both reflecting the regional premium that has built up over the summer months relative to the negative-price conditions seen in May.6,1
The forward question for traders is whether river levels recover fast enough during any break in the heat to allow EDF to restore the constrained 7.3 gigawatts before the next heat episode arrives. Romania's reactor, once cooling conditions on the Danube permit restart, will add some regional relief, but the timeline for that remains unclear from available reporting. With at least five intense heat events already logged this summer and no signal from the source material that the underlying drought is resolving, each temporary recovery in generation now carries the risk of being cut short again before the next wave peaks.7,6