The risk of power blackouts this winter has increased significantly since last year, the National Grid is expected to announce today.
Spare capacity, the difference between the demand for energy and the supply, is believed to be at a seven-year low.
It fell from 15 per cent three years ago to five per cent last year and is expected to be lower again this year.
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A series of fires have curtailed supply, including one at Didcot B power station last week, and earlier this month EDF announced that two nuclear power stations, Heysham 1 and Hartlepool, would produce as little as 75 per cent of their normal output for up to two years.
"The plants were shut down in August after cracks were found in a key structural component at Heysham," says The Times. "EDF plans to return the plants to service over the next two months but at a lower temperature, and therefore lower output, to reduce the risk of more cracks developing."
On top of that, EU rules have required older polluting plants to be closed and uneconomic gas plants have been shut down, says BBC correspondent Esyllt Carr.
The National Grid, which operates the national power network, is due to publish its winter outlook later today and is expected to announce the measures it is taking to keep the lights switched on.
It will pay some power plants to remain on standby and other firms to switch off their electricity during peak demand in winter, which is on weekdays between 4pm and 8pm.
"Critics will seize on the decline in spare capacity as evidence that Britain's energy market is failing," says Carr. "Not least, as those margins are expected to become even tighter next year."
Energy regulator Ofgem has warned that spare capacity could slump as low as two per cent in 2015. The government has announced plans to buy in vast amounts of back-up power, but this will not kick in for another few years.
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