Britain is turning to old coal-fired power units as a “last resort” in case other sources cannot provide enough electricity through the winter as the country faces a wider energy crisis.

Several European governments have requested that back-up power be made available from idled coal plants or those due to close due to lower gas flows from Russia as a result of disputes triggered by its invasion of Ukraine.

Britain’s National Grid said on Thursday it had signed contracts with power generators Drax Group and EDF to extend the life of four coal-fired power units at two plants for the upcoming winter.

The available capacity will only be used a last resort to ensure security of supply if needed, National Grid’s Electricity System Operator (ESO) said, adding that negotiations continue with a third generator for a fifth coal unit.

“These contracts are only intended to be used when all commercial options have been exhausted within the Balancing Mechanism,” the ESO said.

A total of 1,940 megawatts (MW) will be made available from two coal units at EDF Energy’s West Burton A plant, which were due to close this September and two at Drax’s plant in Yorkshire, which ceased commercial operations last year.

The rest at Drax’s plant have been converted to biomass.

The ESO said the upfront cost is expected to be between £220 million and £420 million and the coal-fired units will be available until the end of March 2023.