Around three million households will be able to claim back money from the so-called "big six" energy companies from Wednesday.The move comes after industry regulator Ofgem uncovered accumulated funds resulting from unclaimed balances by customers who had switched to a different energy supplier or moved house.Ofgem in February told the suppliers that they had to return the money or be forced to do so.Affected customers will be able to claim back an average of around £50 each.Ofgem chief executive Dermot Nolan said: “Today’s industry announcement is an encouraging first step by the six largest energy companies to address Ofgem’s call to reunite customers with their cash. It is good news for consumers and if you think you could be owed money we recommend that you contact your previous supplier.“This issue is part of a wider challenge of delivering good customer service that the industry must crack if they are to rebuild customer trust and confidence. And while Ofgem welcomes the progress made to date, suppliers must now do everything within their powers to return the money and prevent a similar situation from happening again. Failure to deliver on the initiatives announced today could trigger further action by Ofgem, including enforcement.”Any money not claimed within two years will be used to support vulnerable customers.The companies have been instructed to ensure they do not build up such large amounts in the future."Today’s announcement is about householders, but the industry has committed to taking a similar approach to small businesses, and Ofgem will hold suppliers to account on their progress in both markets," it added.The big six consists of Centrica-owned British Gas, SSE, EDF Energy, E.ON, npower, and Scottish Power.