Families could save a collective £600 million a year in energy costs by switching gadgets off, a charity has calculated.
More than three-quarters of people admit to regularly leaving at least two devices on standby and 53% admit to leaving the TV on in a room when they are not watching.
The number of people with advanced set-top boxes has gone up by 52% since 2010, and leaving one on standby for 20 hours a day could cost around £20 a year, the Energy Saving Trust said.
Almost half of those who leave their TV on standby do so because it is more convenient and 22% say it is because they cannot access the plug or see no reason to turn it off.
A fifth of people regularly leave multiple televisions switched on in order to not to miss anything when moving between rooms.
Almost a third of people blame their spouse for leaving appliances switched on around the house and almost half blame their children.
Big Energy Saving Week, a joint campaign with the Energy Saving Trust, Department of Energy and Climate Change and Citizens Advice, aims to help people cut their fuel bills and obtain financial support.