Factcheck: How Nuclear, Gas, Wind, & Solar Power Are Affected During Heatwaves

This summer's heatwaves in Europe showed that every type of power plant loses some output when temperatures spike, not just wind and solar. In France, which gets about 70% of its electricity from nuclear power, several reactors shut down or cut output in July because the river water used to cool them got too warm or too scarce, and similar drought-driven shutdowns hit reactors in Hungary and Romania. Gas plants also lose efficiency in heat, and hot, thin air makes it harder for gas turbines to burn fuel efficiently. In the UK, low wind speeds during a June heatwave (wind fell to about 15% of the electricity mix, down from a typical 30%) forced the grid operator to pay steep prices to import emergency power.

Solar tells a different story. Heat does reduce panel efficiency slightly, but heatwaves usually bring long, sunny days, so solar output actually rises overall. In the EU, solar hit record generation in June, and UK homes with panels got the equivalent of about five hours of free daily air conditioning during the same heatwave. The tricky stretch is early evening, when solar fades but demand for cooling stays high, often pushing gas plants (and prices) into overdrive.

Battery storage is increasingly used to smooth this gap, storing daytime solar power for evening use, though batteries too lose some performance in extreme heat. None of this points to an action for your own home, but it explains why summer heatwaves can mean tighter grids and higher electricity prices no matter what powers your local utility.