Full Breakdown
UK Grid Operator Issues Rare Electricity Margin Notices Amid Record-Breaking Heatwave
6/26/2026, 10:08:17 PM
Heatwave Triggers Rare Electricity Margin Notices
The National Energy System Operator (Neso) issued electricity margin notices for the 7 pm–10 pm window on Wednesday, 24 June, and again for Friday, 26 June. The notices requested an extra 1,900 MW on Wednesday and 700 MW on Friday, a measure usually reserved for winter peaks.
Background
A high-pressure heat-dome over western Europe has driven temperatures toward 40 °C, reduced wind, and limited renewable output, while hot river water forced shutdowns at four French nuclear plants and caused some UK gas-fired stations to curtail output.
Data & Statistics
Temperatures hit 36.7 °C in Merryfield, Somerset, and 35.8 °C in West Sussex, with forecasts of up to 40 °C in Norfolk. Neso secured 1.7 GW of imports and paid roughly £10 million on Wednesday, £11 million on Tuesday, and about £4 million for a few hours of gas-plant generation; import prices reached about £1,400 /MWh, nearly twenty times the average electricity market price in June of the previous year.
Official Statements & Responses
Neso called the margin notices a “routine tool” and stressed they “do not mean electricity supply is at risk”, linking the tight margins to “the impact of extremely high temperatures affecting Great Britain and the continent and low wind”.
Criticism & Opposition
The Bakers, Food and Allied Workers Union and the Fire Brigades Union urged strike action on the hottest day, citing the lack of a legal maximum workplace temperature, while major rail operators warned of service reductions.
On-the-Ground Reports
The Met Office issued a rare red weather warning for London, the South East and the East of England; schools closed, hospital appointments cancelled, and health officials warned of heat-related illness.
Conflicting Reports & Gaps
Sources differ on the exact outlay (£10 million vs £11 million) and on demand figures (700 MW, 1,900 MW, or 1.7 GW of imports); the timing of the Wednesday notice’s withdrawal is reported both as a cancellation after 2 pm and as a later decision after payment for imports, and actual generation delivered is not disclosed.
Verbatim Quotes
- “A spokesman for Neso said: “Our forecasts are showing tight margins on the electricity system for tomorrow evening.” — Neso spokesperson
- “This is due to the impact of extremely high temperatures affecting Great Britain and the continent, and low wind.” — Neso spokesperson
- “does not mean electricity supply is at risk” — Neso spokesperson
- “a routine tool” — Neso spokesperson
What’s Next
Meteorological models project continued extreme heat through the weekend, with temperatures possibly exceeding 40 °C again; Neso has signaled that further margin notices may follow if tight margins persist, keeping electricity prices elevated.
