In a consultation paper, Ofgem said that, without intervention, Britain would have a “negative supply margin” this winter, in the event of a one in 20-year cold day — a day so cold Britain would only be expected to have one every 20 years — coinciding with the loss of key gas infrastructure. 

This unlikely scenario is a key standard followed by Britain’s energy authorities to assess its resilience in maintaining gas supply — also called the “N-1 gas security” standard. 

A shortfall in gas supply would be a national emergency, potentially requiring power plants or factories to shut down, or in extreme cases homes being disconnected from the gas network.  

Britain has never experienced a “network supply emergency,” but diminishing domestic supply and the threat of Russian sabotage of key undersea gas pipelines has raised fears over the country’s energy security. 

Last year the energy system operator, NESO, said long-term declines in domestic North Sea gas supply and global competition for LNG imports could mean the N-1 gas security standard is breached in winter 2030/31. 

However, there are now fears of a crunch point as soon as this winter, after the Belgian operator of the undersea gas pipeline Interconnector said it would cut planned export capacity to the U.K. because of soaring maintenance and operating costs. EU countries are also facing concerns over gas supply this winter.