Two-thirds of homeowners have a positive balance on their energy bills and have overpaid by an average of £86.60 per person, though a quarter have a credit balance in excess of £100.
Energy customers can build up a positive balance due to seasonal variations in bills, especially over the summer when consumption is lighter.
Only 11 per cent of almost 1,300 people surveyed said they ask for a refund as soon as their bill is in credit, while 39 per cent usually leave an overpayment with their supplier to smooth out variations.
"Depending on the size of their credit balance, customers should be entitled to a refund," said Ben Wilson, from GoCompare.com Energy.
While each company’s policy differs slightly, automatic credit refunds are typically made at the review date for balances of over £5 where an accurate meter reading has been supplied. However, customers who have built up a credit balance are entitled to ask for it at any time and providers are obliged to refund overpayments unless there are reasonable grounds for withholding it.
Wilson added that the recent collapse of GB Energy, the first domestic energy supplier to close in 10 years, will likely "encourage more customers to tackle their provider" if they see a significant amount of credit build up on their account.
However, Ofgem, the energy regulator, provides a safety net for customers should an energy provider go out of business, removing any risk to your supply, or the likelihood of any financial loss. This includes ensuring consumers will not lose any credit balances.