Holidaying British families could be running up energy bills and damaging the environment - by leaving electrical appliances plugged in and on standby while they are away.
They could be wasting over 1.2 million tonnes of carbon dioxide according to UK power and gas company E.ON.
That is the equivalent weight to 4,000 jumbo jets - and could add a staggering £23 million to UK households' energy bills, said E.ON.
With thousands of holidaymakers set to head off on their summer holidays throughout July and August, E.ON urged people to switch off and unplug appliances before they go away - as they can still guzzle energy even when not being used.
The company said the worst "standby squanderers" are televisions, broadband modems and computers which, if left on standby, can run up hundreds of unnecessary watts.
Head of energy efficiency at E.ON, Phil Biddle, said: "We know families will be looking forward to switching off and relaxing in the summer sun, but taking just 10 minutes to flick the 'off' switch on their electrical appliances before they go away could help save money and the environment.
"If every family in the UK remembered to switch off for summer, we could all make a big difference."
Many appliances such as TVs, microwaves, radios and cookers still use up to 70% of their energy in standby mode, said E.ON.