The company released figures showing a projected shortfall in supply, with the biggest gap forecast in the second week of 2017, when demand will exceed available capacity by 2.3GW.
It predicted that a further six weeks would see a supply gap of more than 2GW, with a further four weeks in which surplus capacity is predicted to be less than 1GW.
However, in a statement to Utility Week, National Grid said: “We publish this information so that suppliers and generators can make decisions and respond accordingly, it is not an indication that there will be supply problems next year. It is a forecast based on current data, current notifications of generator outages and demand forecast.
“The numbers do not include the contribution from interconnectors or the 3.6GW of supplemental balancing reserve contracts we will have available.
“This is a moving picture with figures for nearly a year from now and a lot can happen between now and then.”
National Grid added that more capacity may come online before the winter, an example being the 880MW gas-fired plant being built at Carrington in Greater Manchester.
In December National Grid offered suppliers Supplemental Balancing Reserve (SBR) contracts for 3.6GW of spare capacity in case there are shortages over the winter. Utility Week revealed last week that at least 2.4GW worth of the contracts have now been signed.
Analysts at investment firm Jefferies said: “National Grid’s forecast contains fairly optimistic generation availability assumptions and yet still sees 11 weeks next winter when margins will be negative.
“National Grid is likely to take additional measures ahead of next winter, perhaps by bringing more of the closing coal plant into the SBR. But whether a modern industrial country like the UK should be reliant upon emergency contracts to keep the lights on is another matter.”
National Grid’s projections are based on the assumption that hydro-power plants will be running at full capacity and wind farms will operate at loads consistent with their past performance. It means low winds and reduced rainfall could result in even worse supply gaps.
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