Appliances which are apparently switched off, or which are left on stand-by, use up as much electricity as a washing machine on full cycle and more than a refrigerator, says leading consumer association FACUA.

Brown goods – such as TVs, DVDs and stereos are the worst offenders, although even white goods – kitchen appliances – drink electricity when plugged in but not in use.

Mobile telephones and laptops plugged in overnight to recharge also use up a massive amount of power, so FACUA recommends these are only left on charge for as long as necessary and then disconnected.

And for every 1ºC lower on an air-conditioning unit, the electricity consumption increases by seven per cent, warns FACUA.

In other words, it is cheaper to run the air-conditioning at 24ºC than at 23ºC, but cheaper still at 25ºC.

The average Spanish household uses 10,500 kilowatts in electricity per year, with the lowest consumers being – surprisingly – flats and apartments on the Mediterranean coast, whereas houses further inland and in central Spain use the most, almost twice as much as a flat.

Appliances that use the most power are televisions, followed by microwaves, DVD players, computers, stereo or hi-fi systems, and video-games, in that order.

And satellite decoders of any description use as much energy when switched off but plugged in as when they are in use, FACUA adds.