Threat of electricity brown-out grows as nuclear reactors stay offline

British electricity supplies are now so stretched there is a one in 10 chance of a “brown-out” this winter, the UK’s leading energy analyst has warned.

Concerns are increasing in the sector after it was announced that four nuclear reactors would remain offline throughout the autumn.

Brown-outs see the National Grid turn its voltage down to ration supplies – a practice that generally enables households to function normally but can wreak havoc with certain equipment such as clocks and television set-top boxes.

Peter Atherton, an analyst with Liberum Capital which is considered a leading expert in the field, said the prospect of a brown-out has now leapt to 10 per cent – compared to 0.1 per cent normally – with the potential for a fully-blown blackout slightly lower, at 5 per cent.

“For the first time in a long, long time we might not have enough power stations,” Mr Atherton told The Independent, saying the last time things were this bad was during the three-day week of the 1970s.

Yesterday, EDF, the French nuclear power giant, announced that it would take up to three months longer than planned to service the two nuclear power stations it closed in Lancashire last month after “unexpected cracking” in a boiler unit. These plants produce about 4 per cent of the UK’s electricity.

The nuclear generator closures follow fires earlier this summer at the Ferrybridge and Ironbridge coal-fired plants, which are still out of operation, and the recent announcement that a gas-fired plant at Barking, in East London, is to close.

“There was not much fat left in the system to absorb unexpected shocks – now that fat has gone. At the start of the winter we were four unexpected events away from big trouble – we have had two of those [the nuclear and coal closures], so there are just two left,” Mr Atherton said.

“We have to hope that the weather isn’t too cold, the weather is windy [to help turbines generate electricity] and that we don’t lose another couple of power stations. At the moment the alarm bells are ringing, but softly. If anything else significant happens, the bells are going to go nuts.”

The recent shocks to the electricity system increased the wholesale price of electricity by about 4 per cent yesterday – taking the rise since the end of July to about 13 per cent.

Mr Atherton said he doubted this would push utility prices up this year but, if the higher wholesale price persisted we could see hikes in January or February.

National Grid sought to play down the danger of any electricity outage, saying it had taken the necessary steps to ensure the lights stay on.

“We have already taken the sensible precaution to tender for supplementary balancing reserve this winter, owing to uncertainty over plant availability,” a National Grid spokesman said, adding that this process “is sufficiently flexible to cater for any new information from the market”.