The company is targeting Sky PVRs that are left on between 11pm and 4am without any channel switching or other functions being used.

The screen will display a warning to the viewer, but if there is no response within three minutes the box will power down onto standby.

Sky claims the environmentally friendly move will reduce the UK’s energy usage dramatically – with the amount of power saved being enough to light every house in Wolverhampton and run all the washing machines in Liverpool for a year.

That saving could also cut the country’s carbon emissions by 32,000 tonnes a year.

The Auto Standby’ scheme will start next month.