The survey from comparison website Uswitch.com found that two million households do not know how often their heating comes on during the night to maintain the temperature set on their thermostat.

One in seven households use more than a quarter of their total daily gas consumption between the hours of 11pm and 6am, suggesting that their heating may be coming on while they are sleeping.

Mounting up

Data from users of Uswitch’s energy-tracking app reveals that households use just under 6kWh of gas between 11pm and 6am, costing them 60p a night on average.

They are unlikely to cooking or showering during these times, suggesting gas is being used for heating.

Households typically use just under 3kWh of electricity while they sleep. Fridges, WiFi routers and charging gadgets contribute to the nightly 91p bill. Homes with an electric car will find their night-time energy use to be much higher if they plug their vehicle in for the night.

While lights and televisions should be turned off before going to bed, there are little savings to be made by switching off devices left on standby overnight. In total, routers, TVs and satellite boxes only add about 5p to energy bills a night.

Ways to save

On average, households have their heating on for five hours and 42 minutes over a 24-hour period, but more than one in nine people have their heating on for ten hours a day.

Using a timer is a good way to control when the heating comes on, and households with a smart thermostat can make sure that their home is only being heated when it’s needed.

Cheaper alternatives to leaving the heating on overnight are electric blankets and hot water bottles.

Using an electric blanket for one hour a night instead of using the heating could save £18 a month. Using a 1.5-litre hot water bottle would cut bills by £16 a month.