UK households could get up to £100 off their energy bills as part of a new scheme to help families avoid being affected by blackouts.
The discounts will be available to homes that cut down on their use of energy during peak hours, according to the plans revealed by the National Grid (NG.L).
The move is designed to prevent blackouts and will be tested on 12 days between November and March.
However, only homes with smart meters will be able to take part.
Some 14 million households in England, Scotland and Wales have a smart electricity meter installed. The scheme is also open to businesses.
Customers taking part will be given 24 hours' notice. On the test day they will have to reduce how much energy they use between 4pm and 7pm to qualify for an energy bill discount.
That means they will be asked to delay their use of a tumble dryer or washing machine, or to cook dinner in the microwave rather than the oven.
National Grid will pay energy suppliers for the energy saved and the suppliers will tell customers how much money they will get for taking part.
Individual suppliers will decide how much customers will receive and whether the money is taken off bills, credited to accounts, or if there's an option to withdraw the cash.
This scheme has been named the Demand Flexibility Service by the National Grid which is testing the idea at scale for the first time.
Jake Rigg, director of corporate affairs at National Grid ESO, told the BBC: "It's not a big thing or a difficult thing to do, just remembering to do it 12 times this winter and get that money back, when we are all really struggling with energy bills and the cost of living generally.
"We can all do our little bit, we can shift demand out of that peak and help maintain security of supply throughout the winter.
"Nearly a third of a million households have signed up for a programme to help them save on their energy and reduce the risk of power cuts this winter."
The National Grid has warned that millions of homes and businesses in the UK face planned power cuts this winter in the “extreme” case of gas shortages and reduced electricity imports from the rest of Europe.