How Europe's Fifth Heatwave of Summer 2026 Triggered a Continent-Wide Energy Crisis

EDF itself played down the overall energy loss, estimating it at only 1 TWh in June and 2 TWh in July . But the capacity taken offline at peak moments, and the timing of those losses, is what drove market prices higher and strained grid operations.

Continental Power Price Surge

The heatwave's impact was not confined to France. As French nuclear supply tightened and German wind speeds simultaneously slowed, European spot power prices jumped by more than 20%, with French day-ahead prices hitting summer highs . France normally exports significant amounts of electricity to neighboring countries; with its own output curtailed, those exports fell sharply, putting upward pressure on prices across Western Europe.

The Danube Crisis: Romania's Cernavodă and Hungary's Paks

Further east, a different but equally severe problem was unfolding. The Danube River—which provides cooling water for nuclear plants in both Romania and Hungary—fell to record-low levels. In Romania, the river's flow dropped below 1,500 cubic meters per second, less than a third of the normal July flow . That forced Romania's state-owned Nuclearelectrica to shut down both reactors at its Cernavodă nuclear plant, the first time low water had caused a complete shutdown . Romania declared a national state of alert, and the plant's director said he did not expect a restart within 10 days .

In neighboring Hungary, the Soviet-era Paks nuclear plant—which supplies nearly half of the country's electricity—was forced to cut output sharply as the Danube's receding waters left its cooling intake nozzles unable to reach the river. Output fell to just over 10% of capacity in early August, and Hungary's prime minister warned that a full shutdown—the first in the plant's 44-year history—was imminent . Hungary narrowly avoided a complete shutdown but operated at severely reduced capacity for weeks.

Romania took unprecedented emergency measures, including blasting a rock outcrop and building a dike to redirect cooling water to its sole remaining reactor . The measures bought a few extra days of operation but did not prevent the final shutdown.

Solar's Record Month—and the Problem It Can't Solve Alone

Amid the crisis, solar power delivered a historic performance. According to analysis by energy think tank Ember, solar supplied 25% of EU electricity in June 2026—a record 52 TWh—overtaking nuclear (21%), gas (15%), wind (14%), hydro (12%), and coal (8%) for the first time in a single month . July solar generation reached 55 TWh, maintaining the record share .

The heatwave itself contributed to this outcome: high solar irradiance boosted panel output, while the heat drove a surge in air-conditioning demand that made solar's daytime contribution crucial for meeting peak loads.

But the solar boom came with a familiar structural problem: the