Factcheck: How nuclear, gas, wind and solar power are affected during heatwaves

There's a delicious irony in the fact that the sun—the ultimate source of nearly all our energy—can also be the thing that cripples our solar farms. Photovoltaic panels love sunlight, but they hate heat: for every degree Celsius above 25°C, they lose about 0.5% of their efficiency. On a blazing 40°C day, that's a 7.5% haircut just when demand for air conditioning spikes. It's like a runner who's great in the morning but faints in the midday sun. Meanwhile, gas turbines—the workhorses of the grid—also suffer because hot air is less dense, meaning less oxygen for combustion. They can lose up to 10% of their output. So the grid is already sweating, before we even talk about nuclear. Nuclear power, the stoic giant, has its own Achilles' heel: water. Most reactors use river or sea water for cooling, and when rivers run low and warm—as they do in heatwaves—operators must reduce output to avoid violating environmental limits on discharge temperatures. France, the nuclear champion of Europe, has had to shut down or derate reactors repeatedly during summer heatwaves. It's not a catastrophic failure, but it's a reminder that even the most controlled, engineered systems are still hostage to the whims of a warming planet. And here's the kicker: the heatwaves themselves are made more likely by the very carbon emissions that nuclear power is supposed to help reduce. It's a feedback loop with a cruel sense of humor. But wind power—ah, here's the wild card. Heatwaves often come with strong temperature gradients that drive convective winds, especially in the afternoon and evening. So while solar fades and nuclear throttles, wind can actually pick up. It's not a perfect savior—heatwaves can also bring calm high-pressure systems—but it's a reminder that our energy mix is a chaotic ensemble of actors, each with their own quirks. The grid operator's job is to orchestrate this ballet, and climate change is rewriting the choreography in real time. What fascinates me is the deeper implication: we're building a renewable-heavy grid for a world that doesn't exist yet. We're designing for the climate of the past, while the climate of the future is throwing curveballs. The solution isn't just more solar or more storage—it's smarter, more adaptive systems that can respond to these thermal quirks. Maybe we need solar panels that can sweat, or nuclear plants that can swim. Or maybe we just need to accept that our energy future will be as weird and unpredictable as the weather itself. Read the full factcheck at Carbon Brief: https://www.carbonbrief.org/factcheck-how-nuclear-gas-wind-and-solar-power-are-affected-during-heatwaves.