The electricity and gas network operator for England and Wales is keeping a “close watching brief on supplies as the risk of blackouts was predicted to be at its highest since 2008.

Traditional North Sea gas sources are replaced by “uncertain” imports making it more likely that at any other time in six years that supplies will fall short this winter.

However, the National Grid has said it is confident that the market has the capability to keep the lights on this winter.

Chris Train, director of market operations, said electricity margins - the difference between peak demand and available supply - were “tighter than we have seen historically”.

The reserve margins are forecast to drop from 9% last winter to 4.5% this winter.

National Grid made the gloomy forecast in its Winter Outlook 2013/14, and highlighted reducing gas output from UK territorial waters, primarily in the North Sea.

“Source supplies continue to evolve as UK Continental Shelf (UKCS) gas supplies decline and the UK’s reliance on imports increases,” it said.

“The decline in UKCS supplies and subsequent increase in import capability has materially changed the UK’s gas supply landscape and fundamentally changed the dynamics of supply from that of near predictability to considerable uncertainty.”

Last winter’s repeated and prolonged periods of freezing weather saw a dramatic spike in imports through pipelines to Bacton in Norfolk, from the Netherlands and Belgium.

Daily winter imports from mainland Europe last winter reached 57%, tilting away from traditional UK North Sea and sources.

Traditionally, gas imports flowed from north to south through a North Sea pipeline network based at St Fergus, near Aberdeen, in Scotland.
Last winter coal-fired power generation was increased because of the widening cost differential between coal and gas.

However the availability of coal-fired plants has fallen almost 20% since last winter.

Mr Train said: “While there have been power station closures since last winter, the information suggests that the market can meet demand in cold weather.

“But as the system operator, we’re never complacent and it’s up to us to be ready to balance the system in real time. We believe we are ready and have the tools we need to play our part.”

Wind power helped meet the increased demand last winter, with the amount of power generated from that resource higher than gas-fired electricity levels for the first time.

However, supply needed to be boosted during periods of low wind speed by greater reliance on gas.

Lengthy periods of cold, still weather will further exacerbate gas usage this coming winter.