The unit at Grain can provide enough power for half a million people

Powergen said one unit of its power station at Grain, near Rochester, would come back into action in September.

The move comes amid concern that the closing down of plants following a fall in electricity prices could test the network this winter.

Powergen chief executive, Dr Paul Golby, said: "The reason we've taken this step is to provide more power this winter, when demand is at its highest and wholesale prices are at a level that potentially makes it economic to generate from this unit."

The unit at Grain has a capacity of 650 megawatts - enough to provide power for around half a million people.

Two of Grain's four units have been mothballed for some time with the remaining units following suit in October last year and March.

Dr Golby said it was a short-term move affecting one unit at Grain only.