Running the washing machine at more than 40 degrees Celsius, compared to washing at 30 degrees Celsius, could cost households £16.76 per year, according to calculations by Uswitch.com.

The company asked survey respondents: "How frequently, if at all, do you do any of the following?" in an attempt to gauge the frequency of bad energy habits.

Habits included using the tumble dryer when it's hot outside (42 per cent of households were guilty); letting the hot shower run while not actually in it (39 per cent); and - the most common offence - leaving gadgets on standby (73 per cent).

The washing machine figure of £16.76 was arrived at according to the following reasoning, quoted verbatim: "On average households spend £27.21 a year running their washing machine, based on a 0.712kWh cycle, used three times a week at the energy price guarantee electricity unit rate of 24.50p (0.712kWh x 3 x 52 x 0.245£/kWh = £27.21).

"Which? Research finds washing at 30C uses 38% less energy than washing at 40C.

"£27.21 / 0.62 = £43.89.

"Extra cost of using 40C = £43.88 - £27.21 = £16.67."

The free Uswitch app lets consumers with a smart meter track and reduce their power use to help cut down their energy bills.