Britain's energy firms have been holding on to nearly £4bn of their customers' money, figures obtained by the BBC reveal.

An investigation by Radio 4's You & Yours programme has found that some domestic energy accounts are thousands of pounds in credit. Energy suppliers are under no obligation to tell customers if their credit becomes excessive. However, they must pay back the surplus if homeowners request a refund. Direct debit energy payments spread the cost of gas and electricity evenly across the year. Many customers are often in debit during the winter and build up credit in the summer. Ofgem has previously calculated that a typical customer's credit balance peaks at a little over £100 each year.

'Annoyed'

Figures obtained from energy regulator Ofgem through a freedom of information request reveal that, in October 2015, the UK's energy suppliers held a total of £3.98bn of credit on their customers' accounts. At that time, there were nearly 31 million energy customers in the UK, but the credit is not evenly spread among customers......Read more here