The risk of winter blackouts has increased after a fire affecting a key subsea cable further eroded Great Britain’s backup electricity supply cushion, already diminished by the shutdown of gas plants and nuclear reactors.
The National Grid’s electricity system operator, ESO, said the “de-rated margin” – the amount of excess capacity that could be called upon if needed – was expected to be 6.6% or 3.9 gigawatts (GW).
That would be higher than the margins seen in 2015-16 and the following year. But the ESO said a worst-case scenario, such as multiple power plant outages, low wind speeds, and a bitterly cold winter, could cause the margin plunge to just 4.2%, or 2.5GW.
That would be well below the 5.1% it forecast in 2015, before a notoriously difficult winter when National Grid was forced to ask businesses to reduce their electricity usage to keep the lights on.
With margins likely to be tighter than the Grid would like, it expects to issue a similar number of electricity market notices to last year, when it sent six of the official pleas to energy suppliers to increase the amount of electricity they make available.
The ESO took the unusual step this year of issuing an early version of its Winter Outlook, its annual assessment of Great Britain’s electricity safety net.
It said at the time that the margin could fall to 5.3%, owing to the retirements of the Dungeness B and Hunterston B nuclear power stations and shutdowns at the Baglan Bay, Severn Power and Sutton Bridge gas power stations.
