UP to £235 million of consumers' money may be remaining unclaimed in the closed energy accounts of 2.7 million UK homes, according to a new study.

Despite efforts to reunite the cash with customers, almost a quarter (23 per cent) of consumers admit they are unsure whether they left old energy accounts in credit, says uSwitch.com, the independent price comparison and switching service.

The figures, from a survey of 2,000 UK adults, also reveal that Scots households are not as successful with claims as other parts of Britain.

Around half of Scottish households who switched supplier closed their old account in credit, with fewer than two in three (63 per cent) successfully reclaiming an average of £69 each. Across the UK four out of five (79 per cent) typically claim £18 more.

Some 16 per cent of Scots said they received more than £100 with some claiming more than £200.

Over half (55 per cent) of Scots who have reclaimed credit used it to pay for bills and rent, while 17 per cent put it into savings.

The survey findings, are published six months after the launch of the energy industry's 'My Energy Credit' campaign, launched after after British Gas, EDF Energy, E.ON, npower, ScottishPower and SSE were ordered to repay customers.

The scheme was a response to a demand for action from the regulator Ofgem in February, last year.

Energy UK, the trade association for the gas and electricity sector, said unclaimed credit had typically been left behind by customers who had moved address, had switched suppliers or after closing the estate of a relative who had passed away. The average credit balance, it said, was around £50.

It said the campaign would encourage customers who have switched suppliers or moved home without leaving a forwarding address to get in touch with their old company if they think they have left money behind.

In September, Energy UK said that to help prevent such cash piles building up in future there would be an imposition of a two-year deadline for collection of credit, with any funds left behind after that time being donated to help vulnerable customers.

It later said customers can still apply for their credit repayment "regardless of when the account was closed" as long as there is proof they were a former customer.

uSwitch.com said the study suggests that more can be done to help consumers who have moved or switched supplier to claim any money left behind. There is no time limit on legitimate claims and consumers should check with any previous suppliers to see if they are due a refund.

Tom Lyon, energy expert at uSwitch.com, says: "It's fantastic to see so many households successfully reclaiming what is rightfully theirs, yet almost a quarter could still be missing out on balances left languishing in dormant accounts. With six in ten people admitting they are rationing their energy use to save money, any unclaimed funds could go a long way to helping pay this winter's bills.

"We urge the industry to continue with its campaign to help reunite as many consumers as possible with money from old accounts. It's particularly encouraging to see that almost two thirds of consumers who claimed money back said they found the process easy.

"Consumers should check with any previous suppliers to see if they're due a refund. If you're about to switch, make sure to take meter readings and give them to both companies for a final statement. This will ensure that your old account is closed properly and you receive any refund due."