In a report, the company said there was an "increased likelihood" that it would have to pay large businesses to switch off between 4pm and 8pm during the week. Busineses with 130 megawatts of capacity have signed up to take part in the scheme, which is voluntary. They will be paid for taking part, even if they are not actually called upon - as happened last winter. A further 2.29 gigawatts of power plant capacity that would not otherwise be available will be paid to remain on standby to fire up if needed. Such action would only be taken "as a last resort in the event that there is insufficient supply available in the market to meet demand", it said. Analysis by Ofgem, the energy regulator, suggests that without the emergency interventions, a blackout during a cold snap would be highly likely. The risk of “controlled disconnections”, in which customers’ power supplies are cut off, could have been as high as a “one in one year” event – implying an incident would have been expected at some point during the winter. The tightening of supplies has been caused by the old polluting coal plants being forced to close by environmental rules more quickly than new plants are being built. More coal plants and old nuclear plants are expected to close in coming years, worsening the crisis. The GMB Union, which represents energy workers, has accused the Government and National Grid of complacency with 7.4 gigawatts of capacity due to be lost as nine power stations close during 2016. Ofgem forecasts suggest that by next winter Britain could experience 'negative margins' - meaning output from Britain's power plants would not be enough to meet peak demand - if it is very calm, resulting in low wind turbine output. By 2018/19 a new Government subsidy scheme called the 'capacity market' is due to come into effect, designed to pay power plants to guarantee they will be available to keep the lights on. But that scheme has been called into question after the Telegraph revealed the only new gas plant due to be built through the scheme is in doubt, with its developers unable to secure funding. Expert have warned a solution to keep the lights is likely to require more subsidies to be paid to new plants, raising bills for consumers. Cordi O’Hara, director of UK market operations for National Grid, said: "Electricity margins are manageable throughout the winter period and we believe we have the right tools in place to manage the system. This includes using the 2.4 GW of additional balancing services that we have ready in place for times of highest demand." Amber Rudd, the energy secretary, said: "Keeping the lights on is non-negotiable. National Grid has the right tools in place to manage the system this winter and we will ensure that they continue to do so in future. "Our number one priority is to ensure that hardworking families and businesses have access to secure, affordable energy supplies they can rely on. "In the longer term we are investing in infrastructure and low-carbon energy supplies, such as nuclear and shale gas, to improve energy security for future generations."
The National Grid has announced that the UK's winter capacity is at its lowest in a decade, posing risk of blackouts. However, it states it should be manageable, so long as they are able to enlist power stations to provide the extra capacity. This rising risk of blackouts also means that factories may need to be paid to switch off on weekday evenings, so as to keep household lights on, says the grid. In addition, there will be more than one million homes without electricity for up to two weeks during this winter.