Power system records

Summer delivered a string of extremes on Britain’s power system. Solar passed the 14 GW mark for the first time on 8 July, leaping above the previous 13.2 GW record. Meanwhile, biomass set a monthly record in supplying 9% of the country’s electricity during July. Interconnectors ramped up on 24 August, importing more than 30% of Britain’s demand over the day, the highest on record. An abundance of clean electricity on 6 September saw negative prices plunge to a new low of –£99/MWh, as over 23 GWh of wind output has to be curtailed, costing consumers more than £1.1 million. Finally, nuclear generation slumped to its lowest output this century, dipping below 2 GW on 24 September, as a shortlived trip compounded longer unit outages.

The tables below look over the past sixteen years (since 2009) and report the record output and share of electricity generation, plus sustained averages over a day, a month, and a calendar year. Cells highlighted in blue are records that were broken in the third quarter of 2025. Each number links to the date it occurred on the Electric Insights website, so these records can be explored visually.