The National Energy System Operator issued a rare morning electricity margin notice after forecasting a shortfall of almost 1,400 megawatts, then cancelled it shortly after 9am as the gap narrowed; low wind across Europe and costly Friday imports are behind the squeeze.
Britain's electricity grid operator made an unusual call for help on Monday morning, asking the market for more power after forecasting a shortfall of almost 1,400 megawatts. The National Energy System Operator, known as Neso, issued an electricity margin notice on Sunday night covering 6am to 11am, and said it needed about 800 megawatts of extra generation, roughly the output of a medium-sized gas power station, within eight hours before a review scheduled for 4am.
The gap narrowed through the morning as generators responded. A second notice after the pre-dawn review put the shortfall at 500 megawatts, with no further contingency power required, though Neso said it could still ask plants to run above normal levels between 8am and 11am. A later update cut the shortfall to 200 megawatts, and the notice was cancelled shortly after 9am. Neso called the notice a routine and precautionary measure and stressed that there was no risk to customer electricity supplies and that customers did not need to take action.
The immediate cause appears to have been the weather. Low wind speeds across Europe curbed renewable output towards the end of last week, and the shortfall arrived even though there were no constraints stopping power stations or wind farms from running, and while Britain was forecast to export electricity to Europe. Margin notices of this kind have traditionally been used on cold winter evenings, when demand peaks; the first ones issued during the summer came during heatwaves that pushed demand up while curbing generation.
The shortfall figures are Neso's own forecasts, published in its margin notices through the morning: 1,388 megawatts in the first notice, with an 808-megawatt contingency requirement, then 500 megawatts after the pre-dawn review and 200 megawatts in a later update before the 9.11am cancellation. The Friday import prices, £2,500 per megawatt-hour for power brought in through subsea cables and £1,000 per megawatt-hour to fire up gas plants, are figures given by independent energy consultant Kathryn Porter; Neso's own auction data, examined by the consultancy Watt-Logic, recorded interconnector prices up to £2,541.84 per megawatt-hour that day, which sits with Porter's rounded figure. That the cost of such purchases ends up on household bills follows from how balancing costs are recovered through charges in the energy system.
Friday had already been an expensive day for the operator. Neso paid more than ten times the market price seen earlier in the week to secure electricity imports from Europe, with the cost ultimately recovered through charges on home energy bills. Wholesale gas prices also moved higher on Monday as colder weather was forecast, with the Dutch month-ahead contract up €0.91 to €86.50 per megawatt-hour and the British equivalent up 2.75p to 215p a therm. Neso's latest winter outlook, published in October, forecast a 5.9-gigawatt surplus above peak demand for this winter, a buffer of 9.5 per cent, while acknowledging that tighter periods could still require routine measures such as margin notices.
The episode arrives while Neso is under scrutiny over how it runs the system. An independent investigation published last month found significant and concerning cultural issues inside the operator's control room, after whistleblowers accused it of covering up the growing risk of blackouts and said control-room decisions were subject to interference from the company's corporate affairs team. Neso came back under government ownership in 2024, having previously been part of National Grid, and it is the body responsible for balancing electricity supply and demand across Great Britain minute by minute.