Security of Supply
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Early View of Winter Outlook anticipates highest margins since 2019/20
Security of Supply
18 Jun 2025 - 2
minute read
In our 2025 Early View of Winter Outlook, we’ve set out our initial operational margin expectations for the 2025/26 Winter period, which runs from 31 October 2025 to 31 March 2026.
These margins reflect the excess electricity that is expected to be available, beyond what is used on a second-by-second basis to meet national electricity demand and the reserves of electricity we hold to ensure the safe and reliable operation of the electricity network.
Margins for winter 2025/26
This year’s early view of winter report anticipates an operational margin of 6.6GW (10.9%), which is the highest anticipated margin since the 2019/20 winter and reflects an improved margin of 1GW compared to last year’s Winter Outlook figure of 5.2GW.
What’s caused these improved margins?
This increase in anticipated margin has been driven by a variety of factors reflecting the growth in supply from battery storage, at both the national transmission and regional distribution network levels, alongside an increase in the availability of electricity generation from gas, and the commissioning of the Greenlink electricity interconnector between Ireland and Wales.
Ensuring security of supply
Although our operational view across the winter period is positive there may still be some tight days requiring our control room engineers to use the operational tools at their disposal.
This includes the use of Capacity Market Notices and Electricity Market Notices to inform the owners of electricity generating technologies, like wind farms, batteries or power stations, that additional electricity supplies may be required to meet specific operational needs.
These notices are standard tools used by our control room most winters during the tightest periods of the year and do not mean that electricity supplies are insufficient to meet national electricity demand.
Dr Deborah Petterson, Director of Resilience and Emergency Management, NESO
“Our early view of the winter ahead shows a positive outlook with sufficient margins throughout the colder winter months. We will continue to monitor developments in global energy markets, remaining vigilant in our preparations to ensure that the resilience and reliability of the electricity network is maintained.”
