The government has “war gamed” emergency plans to cope with energy blackouts lasting up to seven days in the event of a national power outage amid growing fears over security of supply this winter.
The Guardian has seen documents, marked “official sensitive”, which warn that in a “reasonable worst-case scenario” all sectors including transport, food and water supply, communications and energy could be “severely disrupted” for up to a week.
They show that ministers will prioritise getting food, water and shelter to the young and elderly people, as well as those with caring responsibilities, if the country experiences blackouts, with the Met Office warning that Britain faces a higher risk of a cold winter.
Whitehall officials are currently stress-testing Programme Yarrow, the confidential plan for coping in the event of a power outage, and have held a series of exercises with government departments and councils across the country in recent days.
The cross-government blueprint was first drawn up in 2021, before Russia’s invasion of Ukraine, to improve planning and resilience in the event of a major technical fault on the National Grid. It is unrelated to the energy outlooks published by the National Grid for this winter.
However, concerns over the impact of a blackout have grown as a result of the war, with government insiders admitting the planning exercises had taken on a new urgency as a result of the resulting energy crisis, which has seen household energy bills spike.
Ed Miliband, the shadow climate secretary, said: “All governments do contingency planning for worst-case scenarios but the truth is that we are vulnerable as a country as a direct consequence of a decade of failed Conservative energy policy.
“Banning onshore wind, slashing investment in energy efficiency, stalling nuclear and closing gas storage have led to higher bills and reliance on gas imports, leaving us more exposed to the impact of Putin’s use of energy as a geopolitical weapon.”
The type of technical fault envisaged by government planners includes flood damage or a lightning strike on a substation, but could also cover an attack by a hostile state on sub-sea power cables, following Russian attacks against the Nord Stream energy pipelines.
The leak comes after a warning from Tom Tugendhat, the security minister, on Monday that Britain had become “more vulnerable” in recent years as countries seeking to do it harm had “levelled the field” by investing time and money into new technologies.
In the worst-case scenario outlined in the plan, only analogue FM radios would work, with just BBC Radio 2 and 4 broadcasting, and uncertainties around local radio as some stations only have a few hours of backup generator cover.
The Guardian revealed last month that the BBC has prepared secret scripts that could be read on air if energy shortages cause blackouts or the loss of gas supplies this winter.
One source said: “The government doesn’t want any publicity on Yarrow, as they don’t want it to be seen as linked to Ukraine, energy supply and the cost of living. But we need to think about how we can help people in advance. The fact they’re talking about it now means they have a real concern it could happen.”
Cabinet Office sources said they did not recognise the claim, as planning was unrelated to events in Ukraine.
Programme Yarrow prepares for a situation where power is unavailable, without any pre-warning, to all premises without backup generators during winter. It envisages that 60% of electricity demand will be met “between day 2 and day 7” when households and businesses will be given “intermittent access” to ration supply.
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An agreement between energy regulator Ofgem and National Grid stipulates that 100% of electricity demand should be restored after a week. The government expects that target to be met even in a worst-case scenario.
“All sectors will be severely disrupted, including communications, transport networks, energy supply, food and water supply,” one document said.
The Yarrow plans prepare for a more severe situation than that outlined by National Grid last month, which warned that Britons could face three-hour rolling blackouts under a worst-case scenario if temperatures drop sharply and Russia cuts off gas supplies to Europe.
Under the electricity supply emergency code, households and businesses will be given 24 hours’ notice of a planned outage, and the plan could be published up to a week ahead on a rolling basis.
The “rota disconnection plan” is designed to cut power evenly across the country. The power cuts should initially only take place once a day for three hours, although it could take up to an hour to reconnect after that. However, the frequency of cuts will depend on the severity of the energy supply shortages.
Jan Rosenow, Europe director at the Regulatory Assistance Project, an energy thinktank, said: “There are so many things coming together at the same time: the gas shortages, high prices, the problems with electricity generation from nuclear plants in France. That’s what causes the concern in government. It is prudent [to plan for outages]. It’s a shame it takes a crisis to have this conversation.”
A government spokesperson said: “As a responsible government, it is right that we plan for all potential scenarios and work with industry to prepare and exercise robust contingency plans. This work is ongoing continuously and is an important strand of our national resilience planning.
“Local and national exercises are a part of this ongoing work and ensure we are able to effectively respond to any of a wide range of scenarios, no matter how unlikely they may be.”