It sounds like the plot of a sci-fi thriller: a blistering heatwave grips the continent, temperatures soar, and yet—somehow—the lights stay on. The hero? Solar power.
But here’s the twist. Just as the sun is saving Europe from blackouts, it also creates a ticking clock. Because when that blazing ball dips below the horizon, the real challenge begins.
A new analysis from energy think-tank Ember has revealed the extraordinary—and precarious—role solar energy played during Europe’s recent heatwaves. And the findings are both a triumph and a warning.
The “Heavy Lifter” in a Scorching Summer
Let’s start with the good news. During the late-June heatwave, solar power stepped up in a big way. Ember’s analysis found that solar output in European countries rose by up to 17% on heatwave days in June and July.
That surge came just in time. As temperatures spiked, so did electricity demand—by as much as 28% in Italy, 23% in Hungary, 14% in France, and 13% in Spain compared with pre-heatwave days. The culprit? Air conditioning. The International Energy Agency estimates that space cooling consumed around seven percent of the world’s electricity in 2022. When the mercury rises, so do the AC units.
But here’s the standout stat: solar was the only major power source to perform “better than usual” during the heatwave. Compared with other days in June and July, average daily solar generation was 17% higher in France and Hungary, 5% higher in Spain, and held steady in Italy.
As senior energy analyst Chris Rosslowe put it: “Solar is already doing heavy lifting during heatwaves”.
The Sunset Problem: When the Sun Checks Out
Here’s where the plot thickens. Solar power is a daytime hero, but it clocks off at exactly the wrong moment.
“The real challenge starts after sundown,” Rosslowe continued. “In the evening, when cooling demand is still high, the grid is most exposed to expensive gas-fired power”.
Think about it: the sun sets, but the heat doesn’t instantly vanish. Office buildings, homes, and hospitals still need air conditioning. People are cooking dinner, watching TV, charging devices. But the solar panels that were cranking out megawatts just hours earlier are now idle.
That leaves a gap. And that gap is currently being filled by fossil fuels—often expensive, imported gas.
The Domino Effect: Heatwaves Are Hitting Everything
If the sunset problem wasn’t enough, the heatwave is also sabotaging other power sources.
- Nuclear and Hydropower in Trouble: Low water levels along the Danube River forced nuclear output to be curtailed in Hungary. Meanwhile, experts warn that hydropower neared an “all-time low” in the Alpine region.
- Coal Plants Struggling: Even fossil fuels aren’t immune. Poland was forced to reduce output at a coal-fired power plant due to critically low water levels in the Vistula River.
- Prices Skyrocketing: The late-June and early-July heatwaves saw average daily electricity prices surge 119% higher in Hungary, 44% in France, 13% in Italy, and 7% in Spain than on comparable days in the preceding weeks.
In short: the heatwave is stressing every part of the energy system. Solar is the one bright spot—but it’s only available half the day.
The Battery Solution: Storing Sunshine for the Night
So, what’s the answer?
Experts say the price surge “reiterates the need for battery storage systems”. If we can store the excess solar energy generated during the day, we can release it when the sun goes down and demand stays high.
Batteries are the missing piece of the puzzle. They turn solar from a fair-weather friend into a round-the-clock ally. And as battery costs continue to fall, the economics are starting to make sense.
But Europe isn’t there yet. Not by a long shot.
The Climate Connection: This Is the New Normal
Here’s the sobering reality: scientists say these back-to-back heatwaves would have been “virtually impossible” if it weren’t for climate change. This isn’t a one-off. This is the new normal.
As heatwaves become more frequent and intense, the demand for cooling will only grow. And the pressure on Europe’s energy grids will intensify.
Solar power is proving its worth. But without massive investment in storage, grid flexibility, and demand management, the sunset will continue to be Europe’s most vulnerable hour.
The Bottom Line
Europe’s heatwave has been a stress test for the energy system. Solar passed with flying colors—during the day. But the evening hours exposed a dangerous dependency on fossil fuels.
The path forward is clear: more solar, yes. But also more batteries, smarter grids, and a recognition that the energy transition isn’t just about generating clean power—it’s about making sure it’s there when we need it most.
Because the sun will always set. But with the right infrastructure, the lights don’t have to go out with it.
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