In houses with drafts, a third of the electricity bill goes right through the window

The advice service said many households will continue to struggle with high energy costs and cold and damp homes despite the recently announced freeze on bills due to a lack of investment in key savings measures such as insulation.

The government’s freeze on energy prices means the average bill will be £2,500 a year from October 1.

However, Citizens Advice reports that more than a million people living in homes with an Energy Performance Certificate (EPC) F rating will face an average bill of more than £3,000.

In addition, drafty and inefficient homes mean they will lose £950 worth of heat paid for through walls, windows and roofs, it has been warned.

It estimated that households would save £8.1bn a year if all homes had a EPC C rating.

Currently, most homes in England and Wales are below this standard, a significant part is pre-war buildings.

There are also regional differences, with people living in Wales, the West Midlands and Yorkshire and Humber face the highest costs, Citizens Advice said.

Almost two-thirds (63%) of homes in these areas have an EPC rating below band C.

Households in London and the South East are likely to be better off, but more than 50% of homes in these regions still have a low EPC rating.

Nearly half (44%) of homeowners are actively considering home improvements, but those who aren’t cited cost as the main reason.

Rich Jones, energy projects manager at Citizens Advice Brighton and Hove, said: “Most of the people we advise are disabled or have a long-term health condition. One person we spoke to is hoping her son will wash her by hand to save on electricity.

“She says she’s cold all the time. Several parents have told us that their children’s bedrooms are so humid that they have given them their room and are now sleeping on the couch or the floor.

“Grants, budgeting and pay checks can only provide short-term relief. But the improvement of their houses would be of great importance.”

Dame Claire Moriarty, chief executive of Citizens Advice, said: “The Government’s emergency bill freeze is putting an end to horrific price rises. Now we need a strategy to get out of this energy crisis.

“Bills are skyrocketing – literally for people in cold and drafty homes with heat seeping in when they turn on the thermostat. This burns the tight budgets of many people.

“Insulating our homes is a long-term solution that will reduce our bills and reduce our dependence on gas. The government should make this a top priority.”