How a Heat Wave Pushed the UK’s Power Grid to Its Limit

5]3ifj2sdlr5am59v(ms}jay_media_dl_1.png NESO

Article content

(Bloomberg) — On a sweltering day in late June, the UK’s power grid came under exceptional strain. As temperatures rose, wind generation slumped and electricity prices spiked, forcing Britain’s grid operator to take emergency measures to keep the lights on.

Article content

The system ultimately held. But fresh analysis shows the grid’s frequency remained below its normal operating level for almost 26 minutes — the longest such stretch on record, according to energy data provider Montel — leaving the system with less margin for error if another problem had occurred.

Article content

Article content

Article content

The findings come as Britain’s grid faces political scrutiny. Shadow Energy Secretary Claire Coutinho has accused the National Energy System Operator of withholding information and risking blackouts, citing whistleblowers who contacted her about actions taken on June 23. While Coutinho hasn’t provided evidence for the claims, and NESO denies wrongdoing, the dispute has drawn renewed attention to the resilience of the UK’s grid.

Article content

Article content

The episode underscores a broader challenge facing Europe. As heat waves grow hotter, longer and more frequent, electricity demand is becoming less predictable just as power systems rely increasingly on weather-dependent renewable generation. That’s leaving grid operators with limited flexibility when conditions don’t cooperate.

Article content

In recent weeks, NESO has issued three warnings asking for additional electricity supplies to maintain a sufficient operating reserve. Such measures are typically associated with winter, when heating demand peaks. But as extreme heat drives up electricity use across Europe, summer is emerging as an increasingly risky season for the region’s power system.

Article content

Article content

“When I was a trader, we were always saying summer is boring,” said Noemie Baud, an analyst at Montel and former senior intraday power trader at Convex Energy. “This is not the case anymore. Summers are as interesting, if not more, than the winters.”

Article content

Emergency Measures

Article content

Weather conditions were particularly difficult on June 23. The UK, like much of Western Europe, was in the midst of a scorching heat wave. Schools were forced to shut, and the authorities issued a red alert for much of the country, warning that the heat could disrupt energy and travel — and might even turn deadly.

Article content

Around midday, the UK generated over 13 gigawatts of solar power, with the renewable source supplying more than a third of electricity to Britain’s transmission network, according to grid data. But by evening, that generation faded. With little wind, the UK was forced to ramp up gas-fired power plants to their highest level since March to fill the gap.

Article content

Signs of trouble soon surfaced. Around 6 p.m., the grid’s system frequency started to fall sharply. The metric, which must remain close to 50 hertz to keep the power system stable, is legally required to stay between 49.5 and 50.5 hertz. In practice, however, it rarely strays outside a much narrower range of 49.8 to 50.2 hertz, according to NESO.