National Grid has has told two coal-fired power stations at Drax to stand down after preparing them to generate electricity amid pressure from freezing weather conditions.
It had asked the winter “contingency” plants to prepare for operation to “give the public confidence in Monday’s energy supply”.
It said the plans meant the coal-fired stations could be used as “tools for additional contingency” as needed to allow the network to run as usual.
However, it told the units they would not be needed later on Monday as there was “adequate available contingency” to power households across the country this evening.
The UK faces its biggest test yet with the current cold snap ramping up demand for power at a time when supplies are tight.
The instruction for the coal-fired plants marked the first since they were put on standby and comes as the grid said it will also run another test of its demand flexibility service – which pays customers to use less electricity during certain hours.
On Monday, customers of some energy suppliers will be asked to reduce their consumption between 5pm and 7pm this evening.
The grid expects that the coal-fired stations will be ready for use if called upon for the evening between 5pm and 9pm, when demand is set to peak.
The stations are operated by Drax and are two of five put on standby under so-called winter contingency contracts, with others run by EDF and Uniper.
The two units are each said to be capable of generating around 570 megawatts – adding more than 1.1 gigawatts to the grid if used.