London, 3 August 2024. The irony is not lost on this correspondent that while Britain endures a heatwave of its own, our cross-channel neighbours are experiencing a far more profound crisis: a partial collapse of their electrical grid. As temperatures in France soared above 42 degrees Celsius on Wednesday, the nation’s ageing nuclear fleet buckled under the dual strain of cooling water shortages and surging demand for air conditioning. At the peak of the emergency, French grid operator RTE was forced to shed 5 gigawatts of load, plunging millions into darkness. Meanwhile, the United Kingdom, thanks to a diversified energy portfolio and robust interconnection, not only kept its own lights on but exported surplus power to the Continent.
Let us be clear: this is not a gloat. It is a sobering lesson in energy physics. A heatwave is a stress test for any electrical system. Demand spikes as fans and air conditioning units are switched on. Supply drops as thermal power plants, from coal to nuclear, become less efficient and require more cooling water. In France, which derives 70% of its electricity from nuclear reactors, the problem is acute. The country’s reactors are predominantly sited along rivers, and when river temperatures rise and flows fall, operators must reduce output or shut down to comply with environmental limits. This is exactly what happened. The Golfech reactor in the southwest was taken offline after reaching the threshold for thermal discharge. Others followed.
Britain has not been immune to these pressures. Our own heatwave has pushed demand near record levels, and some gas-fired plants have experienced reduced output due to high ambient temperatures. But the difference is that we do not rely on a single source for over two-thirds of our generation. The UK’s energy mix today includes gas (45%), renewables (35% wind and solar), nuclear (15%), and a modest but growing contribution from biomass and storage. This diversity provides resilience. When one source falters, others can compensate. Our interconnectors to France, Belgium, the Netherlands, and Norway also serve as a safety net. At the peak of the French crisis, the IFA interconnector was flowing at full capacity from Britain to France, effectively exporting our more stable generation to where it was needed most.
This is not a permanent state of affairs. The UK must also decarbonise its grid, and the path forward is not without pitfalls. Wind power, for instance, can be intermittent. During the current heatwave, wind speeds have been unusually low, reducing output. Battery storage is still embryonic. But the fundamental lesson from this week’s events is that energy security is inextricably linked to diversity. A grid built on a single technology, especially one vulnerable to climate stress, is a brittle grid. The French have long prided themselves on their nuclear prowess, but as the climate changes, they are discovering that those reactors are not as robust as once thought.
For Britain, the takeaway is twofold. First, we must continue to develop a broad mix of low-carbon sources: wind, solar, nuclear, and potentially new technologies like tidal or hydrogen. Second, we must accelerate deployment of enabling infrastructure: interconnectors, storage, and demand-side flexibility. The Climate Change Committee has repeatedly advised that a resilient net-zero grid requires not just generation but also the ability to move and store power. The events in France confirm that advice.
There is a deeper truth here, one that chills the spine of any climate scientist. This heatwave, like those before it, is made more intense by anthropogenic warming. As global temperatures rise, such extreme events become not just more frequent but more severe. A 42-degree day in Paris would have been a statistical rarity a generation ago; now it is a chronic threat. The French grid collapse is a warning to all nations. Our energy systems, designed for the stable climate of the 20th century, are now being warped by a changing climate. Resilience is not a luxury but a necessity.
Britain should take this moment to reflect. We have, for now, dodged the worst. But the same fundamental physics that felled France applies here. Our gas power plants are also susceptible to heat and drought. As the climate continues to warm, we will face our own tests. The solution is not to double down on any one technology but to embrace a systems approach. Smart grids, distributed generation, storage, and interconnectivity are the keys. The UK Government’s recent acceleration of renewable targets and approval of new nuclear at Sizewell C are steps in the right direction. But we must move faster, and with a clearer understanding that energy security in the 21st century is synomymous with climate resilience.
In the meantime, spare a thought for the French. Their plight is not a failure of will but of physics. And we will face the same physics soon enough.
