Ofgem is responsible for regulating gas and electricity supply, including customer payments. Gas and electricity suppliers customarily review individual customers' direct debit arrangements annually. The payments are adjusted in the light of the customer's energy use over the previous 12 months and any changes in energy prices in order to avoid excess credit balances. Generally any credit built up over the summer will be used to offset the customer's higher consumption expected during the winter.Suppliers set their own level of credit a customer must hold before a refund is offered automatically but customers may review their gas and electricity accounts and discuss the level of payments with their supplier at any time, and may request a manual credit refund based on a meter reading.