On 23 June, as France experienced one of its hottest days on record, the Eiffel Tower closed early, and in the town of Ergué-Gabéric, Brittany, a transformer failure cut power to over 100,000 people. The incident, described as "heat related" by local authorities, was confirmed by RTE, the French power company, which had the day before stated there was "no concern" about electricity availability. These events highlight a growing challenge: essential technology, from power infrastructure to healthcare systems, fails when temperatures rise.
Heat-Related Infrastructure Failures
"Anything to do with the electricity network – the power lines, the interconnectors and transformers – they all struggle to keep themselves cool enough," explains Iain Staffell of Imperial College London. This reduces efficiency across the board. Power lines, made of metal, expand in heat, causing them to droop. "There is a limit to how much droop you can allow," says Simon Hogg, a consultant and professor emeritus at Durham University. If sagging cables touch trees or buildings, they can cause accidents or power failures—a scenario that led to the massive 2003 blackout in North America. To mitigate this, operators reduce the electricity sent along power lines during heatwaves, limiting supply.
Impact on Critical Systems
The problem extends beyond energy. Last week, six NHS trusts in England declared a critical incident after hot weather adversely affected their IT systems, scanners, and cancer and lab equipment. This disruption to healthcare technology underscores the vulnerability of essential services to extreme temperatures.
Energy Sector Vulnerabilities
Staffell and colleagues estimate that at 40C, gas-fired power stations' output drops by roughly 10% compared to 20C. Solar panel efficiency also falls as temperature rises, though newer generations show less pronounced effects. In Great Britain, data analysed by Staffell shows that solar output plateaus above 27C and then slowly declines as temperatures continue to rise. However, extended sunny periods during heatwaves can still boost solar output relative to cloudier days before the heatwave, as noted by comparison website Utility Bidder.
| Temperature Effect | Impact | Source |
|---|---|---|
| Gas-fired stations at 40C vs 20C | ~10% output drop | Staffell, Imperial College London |
| UK solar output above 27C | Plateaus and slowly falls | Staffell, Imperial College London |
| Power line droop | Limits electricity transmission | Hogg, Durham University |
Adaptation and Resilience
UK energy networks are currently implementing climate resilience strategies, according to the Energy Networks Association, an industry body. Overall, Hogg describes the UK's energy systems' ability to cope during heatwaves as "a success story." But as more frequent and intense heatwaves triggered by human-caused climate change become the norm, engineers are increasingly adapting infrastructure. The June heatwave, with temperatures around 40C in France, serves as a stark reminder that technology has its limits—and that preparation is essential for maintaining reliability.
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