Europe’s extraordinary summer heatwave is exposing an uncomfortable truth about modern energy systems: electricity may be generated from uranium, gas, coal, wind or sunlight, but much of the infrastructure still depends on something increasingly unreliable — water.
The Danube has become the most dramatic example. Romania has now shut down both reactors at its Cernavoda nuclear power station after the river fell to historically low levels. The plant normally supplies around a fifth of Romania’s electricity.
Hungary’s Paks nuclear station has also been operating at sharply reduced output as the Danube struggles to provide sufficient cooling water.
Emergency engineering measures have even been considered to raise water levels around the plant.
But this is not simply a Danube problem
France’s huge nuclear fleet is facing a different version of the same challenge. Several reactors have been shut down or had their output reduced because rivers and seawater have become too warm.
Nuclear plants need enormous quantities of cooling water, but environmental rules restrict how much additional heat can be discharged into rivers when their temperatures are already dangerously high.
As of 13th August 2026, almost 20% of French nuclear capacity was unavailable, with the heatwave expected to force further reductions.
Jellyfish blockage
France has also encountered a rather more bizarre cooling problem. At Gravelines, one of Europe’s largest nuclear stations, huge quantities of jellyfish clogged seawater intake systems, forcing three reactors temporarily offline.
Warmer seas may make such biological disruptions more frequent
Elsewhere, Italy, Poland and Slovenia have also experienced power-plant restrictions linked to low river levels or excessive water temperatures.
Slovenia’s Krško nuclear plant, for example, reduced output because of hydrological and meteorological conditions affecting the Sava River.
The problem extends beyond nuclear: coal, gas and other thermal power stations also require cooling, while drought reduces the water available for hydroelectric generation.
UK gas heats up
Britain has not escaped the problem. During an earlier heatwave, five major gas-fired power stations reportedly had to reduce output because high temperatures made cooling more difficult.
The UK grid has also been under unusual summer pressure as air-conditioning demand rises, power-plant efficiency is affected and electricity imports become more important.
The bigger warning
Climate change does not simply mean hotter weather. It means the simultaneous arrival of several stresses: higher electricity demand for cooling, lower river flows, warmer cooling water, drought, wildfires, reduced hydroelectric output and pressure on transmission infrastructure.
Irony
The irony is striking. We build power stations to protect society from the weather, yet increasingly extreme weather can interfere with the very systems designed to keep the lights on.
Europe’s energy challenge is therefore becoming a climate-and-water challenge as much as an electricity challenge.
Future power stations may need alternative cooling systems, greater water efficiency, more storage, stronger interconnections and a much wider mix of generation.
Water security
The lesson from this summer is uncomfortable but simple: energy security depends on water security too.