A survey by Age UK found that three million older people could be affected right across the country.
On Thursday, ScottishPower became the fourth of the “big six” suppliers to bring in huge rises in energy bills, following British Gas, SSE and npower.
The Age UK poll of 1,100 over-65s also found that more than half were concerned about the increasing costs of energy.
The survey, marked to launch its Spread The Warmth campaign, also found that many are unaware of health problems linked to the cold.
Caroline Abrahams, charity director, said: “It’s vital for older people to keep warm, both inside and outside their homes in the winter months.
“Being cold, even for just a short amount of time, can be very dangerous as it increases the risk of associated health problems and preventable deaths during the winter.”
Meanwhile another study has found that pensioners are facing a long and lonely winter with little or no contact with their neighbours.
Almost a million of those over 75 admit to not even knowing who lives next door – leaving them at risk of isolation and without crucial support during bad weather and dark evenings.
Thirty per cent of older people only have a conversation with their nearest neighbours once or twice a month and 11 per cent say they never speak to them, according to the charity Royal Voluntary Service – formerly the WRVS. With 23 per cent of older people admitting they are lonely, neighbours are more important than ever.
When getting out and about is difficult, loneliness can set in, which can have a serious impact on health and well-being
David McCullough, chief executive, said: “It takes a small change to make a big difference to the lives of older people who may not see anyone other than their neighbours for days on end.
“When getting out and about is difficult, loneliness can set in, which can have a serious impact on health and well-being.”
The charity is calling on neighbours to keep an eye on the elderly this winter. It provides a “good neighbours” service which, through its 40,000 volunteers, helps older people get out of the house, see friends or run errands. But more people are needed to help out.
For more information visit royalvoluntaryservice.org.uk or call 0845 600 5885.