UK households could save an average of £147 per year by switching off so-called vampire devices, British Gas research suggests.
These are electronics that drain power even when they are on standby.
The figures are based on research conducted on appliances in 2019 but have been updated by British Gas to reflect recent price increases.
The Energy Saving Trust (EST) said consumers need to consider which devices they leave switched on.
It estimates households would save around £55 per year by switching off all their devices when not in use.
The organisation, which promotes sustainability and energy efficiency, did not give exact details of how it came to this figure.
"Stats or prices related to individual appliances depend on several factors, including model, functionality and individual usage," it said.
Brian Horn, Senior Insight and Analytics consultant at the EST, said there were practical things consumers could do.
"If something doesn't need to be on, then you should switch it off at the wall or unplug it," he said. "Everything else, just try and make it as easy as possible to turn it off.
"If you make sure that the plug is accessible, if you can just switch it off, so you don't need to unplug it.
"But if you've got a whole bunch of things plugged in behind your television, you maybe want to plug them all into one extension lead."
A 54% rise in the energy price cap has meant a household using a typical amount of gas and electricity will now pay £1,971 per year.
Bills could be set to rise even higher, Energy UK deputy director Dhara Vyas told BBC News.
She said some estimates suggested households could see bills of up to £3,000 this winter.
As long as devices are plugged in at the wall, they are slowly drawing power.
It may be convenient to leave the television on standby and wake it up with a press of a button on a remote, but this can be expensive.
British Gas used average costs of wattage from different manufacturers' average models when left on standby to calculate its figures.
It says a TV clocks up £24.61 per year, while a set-top box from Sky or Virgin Media can incur £23.10.
British Gas says games consoles left on standby work out at an average of £12.17, while computers could cost about £11.22.
And there's more:
- Microwave: £16.37
- Shower: £9.80
- Washing machine: £4.73
- Printer: £3.81
- Phone charger: £1.26
It says its figures are in line with figures from the EST in terms of the percentage of electricity used by "vampire devices".
According to the EST, between 9% and 16% of electricity consumed in homes is used to power appliances when they are in standby mode.
The British Gas research is based on 13 standard appliances, but according to the EST, the average household has 41 electrical appliances, so the costs could be even higher than estimated.
Newer devices will be more energy efficient than older ones - newer TVs will have to comply with EU standards on energy efficiency.
British Gas energy expert Marc Robson recommends adding devices to an extension lead that can be switched off at night - or using smart plugs that allow you to turn devices off with your phone.
He also made some other suggestions:
- Try not to overcharge your mobile phone and laptop unnecessarily.
- As soon as your device is charged, try and get into the habit of unplugging it.
- A smart meter's in-home display can help to identify how much energy is used at different times of the day, so you can see where energy is wasted.
This piece has been amended to make clear that the £147 estimate was from British Gas research and to include figures from other bodies