Some UK households could be granted discounts if they cut their energy use between 5 and 6pm on Monday. 

The National Grid ESO has ordered three UK coal plants to increase available electricity supplies amid forecasts of supply margins that are "tighter than normal". 

It also intends to activate the "demand flexibility service (DFS)" for the first time which allows the ESO to access additional flexibility when national demand is at its highest.

The scheme entitles some households with smart meters to discounts if they cut their use of electricity.

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It is due to stay in place until March, with 26 energy suppliers including Octopus Energy and EDF signed up to it, but until now has only been used in tests.

National Grid ESO added that its announcement should not be interpreted as a sign that electricity supplies are at risk and said “people should not be worried”.

“These are precautionary measures to maintain the buffer of spare capacity we need,” National Grid said in a tweet.

The cold weather means more people are heating their homes which increases demand for energy, but a lack of wind has reduced the amount of renewable energy available.