- Neso initially forecast a 1,388MW shortfall in its electricity supply margin.
- The gap narrowed through the morning before the notice was cancelled.
- Low wind generation across Europe and costly power imports have renewed questions about energy security and consumer bills.
Britain's electricity grid operator made an unusual call for extra power on Monday morning after forecasting a tight supply margin, with weak wind generation across Europe adding pressure to the energy system.
The National Energy System Operator (Neso) issued an electricity margin notice on Sunday night, warning that the gap between expected electricity supply and the reserve capacity it wanted to maintain could reach 1,388 megawatts between 6am and 11am on November 9.
The operator initially sought around 800MW of additional generation, equivalent to the output of a medium-sized gas-fired power station. However, the situation improved after market participants responded to the notice. A pre-dawn review reduced the forecast shortfall to 500MW, before a later update brought it down to 200MW. Neso cancelled the notice shortly after 9am.
The alert did not mean Britain was running out of electricity. Neso stressed that it was a precautionary measure intended to secure additional capacity and maintain a comfortable operating margin.
A spokesperson said: “We have issued an electricity margin notice for tomorrow (Monday) morning, as a routine and precautionary measure, giving market participants the opportunity to make additional generation capacity available.”
The spokesperson added: “This is not a warning of power cuts, there is no risk to customer electricity supplies, and customers do not need to take action – Great Britain’s electricity system remains secure.”
Why was the electricity margin notice unusual?
Electricity margin notices are used when Neso wants more spare capacity available to balance the system. They give generators and other market participants an opportunity to make additional electricity available if required.
Such notices have traditionally been associated with cold winter evenings, when household and business electricity consumption tends to rise sharply. Monday's alert was unusual because it covered the morning period, between 6am and 11am.
The immediate pressure appears to have been linked to low wind speeds across Europe, which reduced renewable electricity generation towards the end of the previous week. Wind output can vary significantly with weather conditions, making it harder for grid operators to predict how much electricity will be available at any given time.
The notice was issued even though there were no reported network constraints preventing power stations or wind farms from supplying electricity. Britain was also forecast to export power to Europe, suggesting the concern was not simply a lack of available generation across the domestic network.
The situation highlights a wider challenge for electricity systems increasingly reliant on renewable sources. Wind and solar can provide substantial amounts of low-carbon power when conditions are favourable, but their output is weather-dependent. Operators must therefore maintain enough flexible generation, storage, imports or demand-side response to manage periods when renewable output falls.
Neso's alert followed a period of tighter electricity margins in recent months. The operator issued its first margin notices during the summer, when heatwaves increased demand while also affecting generation.
Could the pressure lead to higher energy bills?
The cost of securing additional electricity is another concern, particularly when supply is tight across neighbouring markets.
On Friday, Neso paid more than 10 times the market price seen earlier in the week to secure electricity imports from Europe. Independent energy consultant Kathryn Porter said the payments included £2,500 per megawatt-hour for electricity imported through Britain's high-voltage subsea cables and £1,000/MWh to bring gas-fired power stations into operation.
Such costs are ultimately recovered through charges within the energy system, which can feed into household bills.
Wholesale gas prices also moved higher on Monday amid colder weather forecasts, which raised expectations of increased heating demand. The Dutch month-ahead gas contract rose by €0.91 to €86.50 per megawatt-hour, while the equivalent British contract increased by 2.75p to 215p a therm.
Energy markets were also monitoring developments in the Middle East, particularly the conflict involving Iran and the security of shipping routes around the Strait of Hormuz. Brent crude fell 0.6 per cent to just under $96 a barrel on Monday after US president Donald Trump played down the likelihood of further American strikes on Iran while negotiations continued.
The electricity margin notice also arrives as Neso faces scrutiny over its internal operations. An independent investigation published last month found significant and concerning cultural issues within the operator's control room. It followed whistleblower allegations that the organisation had sought to conceal growing risks to electricity supplies and that corporate affairs staff had interfered with operational decisions.
The investigation's findings have added to questions about how the organisation manages pressure on the electricity system, although the allegations should be distinguished from the findings themselves.
Neso returned to government ownership in 2024 after previously operating as part of National Grid. Its role is to balance electricity supply and demand continuously while planning for the longer-term needs of the energy system.
Its latest winter outlook, published in October, forecast a 5.9GW surplus above peak electricity demand for winter 2026-27, representing a 9.5 per cent buffer. The operator said supplies were expected to remain secure, while acknowledging that tighter periods could still require routine measures such as margin notices.
Monday's alert therefore does not point to an imminent blackout. It does, however, illustrate why maintaining a reliable electricity system requires more than building renewable generation. Britain also needs sufficient backup capacity, stronger networks and effective ways of managing periods when weather-dependent power output falls
