The weather phenomenon driving up Britain's electricity bills

Telegraph

12-07-2025

A surge of windless heatwaves hitting Britain this summer is wreaking havoc on electricity markets and driving up bills for consumers, according to energy experts.
The industry is already familiar with 'dunkelflautes' – the increasingly common spells of freezing windless winter weather when wind and solar farm output plummets. Now it is reporting a similar 'hitzeflaute' phenomenon in summer, with longer spells of warm windless weather also becoming more prevalent with climate change.
Hitzeflaute comes from hitze – the German word for heat – and flaute, which means lull, reflecting the absence of strong winds in such spells.
It means Europe and the UK are becoming increasingly dependent on solar power during the day but, in the absence of wind, having to ramp up gas, coal and nuclear power stations in the evening.
The phenomenon also causes massive market swings with power prices often going negative in daytime when solar is peaking, but surging up to £200 or £300 per megawatt hour when the sun goes down, especially if wind output is low.
The UK faces just such a spell this weekend, with a high pressure weather system bringing clear skies, sunshine and low winds that will coincide with the Wimbledon tennis finals.
'These spells are becoming longer and more frequent and hitzeflaute is emerging as the new term for them,' said Jean-Paul Harreman, a senior analyst at Montel, which specialises in European energy data and convening the first conference on hitzeflautes this week.
'The weather is changing at a time when the energy transition is making us more dependent on the weather to generate our electricity from wind and solar. So it is all causing a degree of chaos in the energy markets.'