We built a power grid to watch winter. Summer is coming for it.
A heatwave won't break Britain's grid — we hedged that risk almost by accident. But the very reason we're safe is why nobody is watching the summer risks that actually are coming.
When a heatwave settles over Britain, we've learned which parts of the country to worry about. The railways, where the steel rails buckle and the trains slow to a crawl. The hospitals, where the wards climb past what the patients can bear. The schools that send the children home early; the roads that soften and rut under the traffic. It's a familiar list of infrastructure that was never really built for this — and over the last few summers, quietly, we've added a new name to it: the electricity grid.
On 23 June this year it earned its place on the list. A hot, still afternoon, a grid visibly under strain, and — for once — people asking out loud whether the two were connected. That question turns out to have a more interesting answer than either side of the row assumed. So let's ask it properly: can Britain's grid actually cope with the heat?
France supplies the version that makes the front pages. Its nuclear fleet sits on rivers — the Rhône, the Garonne, the Loire — and when those rivers warm past their environmental limits, the reactors have to throttle back to avoid cooking the water downstream. Across the 2026 season, EDF's own outage register shows French reactors filing 43 environmental-restriction shutdowns on river sites, 5 on the Blayais estuary, and zero on the coast. Same operator, same regulator, same heatwave. The only variable was what the reactor uses to shed its heat.
And it isn't only the reactors. The same hot, dry summers that warm the cooling rivers drain the reservoirs behind them — back in 2022, hydropower slumped from the Alps down into Norway as the drought bit. Water is continental Europe's quiet exposure to the heat, whether it's cooling a reactor core or spinning a turbine.
So: can Britain's grid cope? The honest answer is yes — comfortably — and mostly by accident. Which is the good news. It's also, as we'll get to, the problem.
First, the reassurance: it won't melt
Britain drew three lucky cards, and they're worth understanding before we ruin the mood.
The first is that every nuclear reactor we have sits on the coast, cooled by the sea. The sea is a spectacular heat sink: it barely warms across a single hot day, and — the part everyone misses — it peaks weeks after the air does. Put 45 years of satellite sea-surface temperature next to the Central England air record and the lag is stark:
