Britain’s grid operator will for the first time this heating season pay households to cut electricity usage on Wednesday evening as cold weather and low winds tighten supply.

The so-called Demand Flexibility Service will be activated between 5 p.m. and 6:30 p.m. local time, National Grid ESO said in a statement. The tool, already tested at the peak of Europe’s energy crisis last year, is meant to encourage eligible properties with smart meters to shift power usage outside of peak hours.

“Our forecasts show electricity supply margins are expected to be tighter than normal on Wednesday evening,” ESO said. “It does not mean electricity supplies are at risk and people should not be worried. These are precautionary measures.”

The operator plans to reach a maximum demand reduction of 459 megawatts during the event, according to a separate notice.

While ample natural gas supplies, higher renewables capacities and lower fuel demand from industries have put Europe on more stable footing for this winter, many energy networks across the region — Britain included — have kept their tools for navigating the supply-demand balance from the last heating season.

A cold spell is expanding from Europe’s north this week, with snow and ice weather warnings for parts of Britain already in place. Minimum temperatures will be as low as -1.5C in London on Friday and Saturday, according to forecaster Maxar Technologies. That will drive up gas demand just as wind-power generation remains sluggish.

--With assistance from Rachel Morison.

(Updates with a planned demand reduction in fourth paragraph)