Consumers are being urged to check their old energy accounts after new research found that up to £235 million, or £88 per account, could be lying unclaimed.
Almost a quarter of customers (23%) who switched suppliers with uSwitch admitted they didn't know whether they were in credit on their old accounts or not.
More than half (52%) of households that switched supplier had credit remaining in their account, with 79% of the successfully claiming an average of £88 each. A quarter got back more than £100 and a lucky 2% of switchers had more than £300 returned to them.
Some 53% of people who did receive what was rightfully theirs used the money to pay bills and rent, while another quarter (24%) put it into savings.
uSwitch's survey also revealed that just over a third of energy consumers said they were cutting back on the amount of energy they use to make their bills cheaper, with a further 22% planning to do the same in future.
The findings come six months after the energy industry launched the My Energy Credit Campaign, which aims to encourage customers to reclaim their cash from their old suppliers.
Tom Lyon, energy expert at uSwitch.com, said: "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.
He added: "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."