Millions of homes in Britain could be hit by blackouts this winter if there is a prolonged cold snap, a report warned yesterday.
The prediction was made by the National Grid, which revealed that the "safety cushion" between peak electricity demand and generating capacity had fallen to dangerously low levels. It said that the danger of blackouts would be highest in the four weeks either side of Christmas.
The problem stems, in part, from generating companies mothballing power stations because of the slump in wholesale electricity prices that followed a government shake-up of the market. London and the Midlands were hit by blackouts in August and September but in both cases the power cuts were caused by failures in the transmission system.
The report said that if there were blackouts this winter the cause would be the shortage of power stations.
Britain came close to a power cut last winter when the safety cushion between demand and available capacity fell to 2 per cent on the evening of 10 December.
In normal circumstances, the grid likes to have a safety margin of at least 20 per cent. This winter, the report calculated that the margin would fall to 7 per cent, with 55.7 gigawatts of peak electricity demand against 59.5 gigawatts of available capacity.
But it said that this slender safety margin could vanish if there was a prolonged cold snap and the interconnectors that provide England and Wales with extra power from Scotland and France were unable to operate at full pelt.
Ofgem, the energy regulator, sought to play down the situation yesterday, saying that National Grid Transco "does not anticipate power cuts this winter". But Alistair Buchanan, Ofgem's chief executive, conceded that blackouts could not be ruled out. "No system can ever offer a 100 per cent guarantee when faced with unexpected events," he said.
The report said that the prospect of blackouts being caused by a prolonged spell of cold weather, a shortage of emergency supplies from France and Scotland and the failure of gas-fired power stations to switch over to alternative fuel sources was a "worst case scenario".
The report added: "While each of these scenarios is credible, there is a low probability of them all occurring concurrently." But energy experts pointed out that it was just such a sequence of unexpected events that led to August's blackout in the capital.
The power cut was caused by a "sod's law" combination of an incorrectly fitted fuse tripping after the emergency shutdown of a substation, when a back-up transmission line was out of service for planned maintenance.
Concerns have been heightened by recent blackouts in other countries - notably the United States, Italy and Scandinavia.
Ofgem insisted that "market mechanisms" would ensure that there was always enough generating capacity to meet demand, and said that mothballed plants had already started to come back on line in response to a 25 per cent increase in wholesale prices in the past 12 months.
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