Campaigners are calling on householders to help elderly friends and relatives find cheaper energy deals after finding that almost nine in 10 bill payers did not switch in the last year.
The new figure from Ofgem, based on data from household meters, found that 88% of energy customers have not switched in the last year despite widespread advice that doing so can save hundreds of pounds.
A separate poll for Big Energy Saving Week, a joint campaign with Energy Saving Trust, Department of Energy and Climate Change and Citizens Advice, found 45% of people did not believe they could save money by switching and 75% of people who did thought it would be £100 or less.
A fifth (20%) said they were aware that an elderly person they looked after had fallen behind on their energy bills or been unable to pay.
Energy Saving Trust chief executive Philip Sellwood said: "We're urging sons, daughters, friends, neighbours and even older people themselves to help each other, or someone they know, to check and make sure they are on the best deal online or over the phone."
The poll also revealed a number of misconceptions about switching, with a quarter of people wrongly thinking that tenants needed their landlord's permission to switch and 25% worrying that they could be disconnected when changing supplier.
Citizens Advice chief executive Gillian Guy said: "Myths about energy bills and switching are standing in the way of savings.
"Consumers can cut their gas and electricity bills by shopping around and switching to a new deal.
"Whether you are a tenant in a private rented property, own your own home or have a pre-payment meter there are savings to be made.
"While the process is fairly straightforward not everyone feels confident to find the best tariff and some are put off by myths around switching.
"That's why we're running Big Energy Saving Week to help people find the cheapest deal before temperatures really start to drop.
"Help and information is available online, over the phone, or by attending one of the hundreds of events across the country."
Energy and Climate Change Secretary Amber Rudd said: "By not switching, hardworking bill payers are missing out on hundreds of pounds, savings which could especially help older people heat their homes for less this winter. "
:: Ipsos Mori surveyed 2,710 UK adults between September 21 and October 1.