A scheme that offers discounts on bills for households who cut peak-time electricity use will be triggered on Monday as the UK's cold snap continues.
National Grid ESO said it would activate the scheme, which has only been used in tests until now, between 17:00 and 18:00 GMT.
It has also asked for three coal-fired generators to be warmed up.
National Grid ESO said the measures were "precautionary" and it did not mean electricity supplies were at risk.
It said it expected electricity supply margins "to be tighter than normal" on Monday, but added that "people should not be worried".
"These are precautionary measures to maintain the buffer of spare capacity we need," it said.
The cold weather means demand for energy rises as more people heat their homes.
To try to reduce demand, National Grid ESO has activated its "demand flexibility service", which allows some households to receive discounts if they cut their use of electricity, by, for example, delaying the use of a tumble-dryer or washing machine.
The scheme is available to homes with smart meters and whose energy supplier is signed up to it.
According to National Grid ESO, 26 suppliers have joined the scheme, including British Gas, EoN, Octopus Energy and EDF, and more than a million households and businesses have now signed up to take part.
The scheme was introduced last year and is scheduled to run until March.
National Grid ESO has also ordered three UK coal plants to begin warming up in case they are needed to generate electricity.
Power station operator Drax has been asked to prepare two coal-fired units and EDF is warming up its West Burton plant.
A similar request to warm up coal plants was made in December last year, although in the event they were not used.
Last summer, the UK government asked Drax to extend the life of its coal-fired generators due to fears over the security of energy supplies following Russia's invasion of Ukraine.
The Drax plants had been due to close in September, but the company agreed to keep them online until March 2023.
National Grid's boss told the BBC last year that blackouts would be a last resort this winter if energy supplies run low.
John Pettigrew said National Grid's "base case" assumption was the UK would have enough supplies to meet heating and lighting demand.
It has also asked for three coal-fired generators to be warmed up.
National Grid ESO said the measures were "precautionary" and it did not mean electricity supplies were at risk.
It said it expected electricity supply margins "to be tighter than normal" on Monday, but added that "people should not be worried".
"These are precautionary measures to maintain the buffer of spare capacity we need," it said.
The cold weather means demand for energy rises as more people heat their homes.
To try to reduce demand, National Grid ESO has activated its "demand flexibility service", which allows some households to receive discounts if they cut their use of electricity, by, for example, delaying the use of a tumble-dryer or washing machine.
The scheme is available to homes with smart meters and whose energy supplier is signed up to it.
According to National Grid ESO, 26 suppliers have joined the scheme, including British Gas, EoN, Octopus Energy and EDF, and more than a million households and businesses have now signed up to take part.
The scheme was introduced last year and is scheduled to run until March.
National Grid ESO has also ordered three UK coal plants to begin warming up in case they are needed to generate electricity.
Power station operator Drax has been asked to prepare two coal-fired units and EDF is warming up its West Burton plant.
A similar request to warm up coal plants was made in December last year, although in the event they were not used.
Last summer, the UK government asked Drax to extend the life of its coal-fired generators due to fears over the security of energy supplies following Russia's invasion of Ukraine.
The Drax plants had been due to close in September, but the company agreed to keep them online until March 2023.
National Grid's boss told the BBC last year that blackouts would be a last resort this winter if energy supplies run low.
John Pettigrew said National Grid's "base case" assumption was the UK would have enough supplies to meet heating and lighting demand.