Householders who use pre-payment utility meters end up around £100 out of pocket by not switching their supplier, Ofgem said today. Pre-payment customers could save money by getting their gas and electricity from separate firms. However, many remain unaware of the potential savings, according to the energy regulator. It found npower to be the most expensive electricity firm for pre-payment meter customers, charging an average £435 a year. Scottish and Southern was the cheapest at £356. British Gas was the most expensive gas firm with average annual rates of £617. Ofgem said the potential savings for users of pre-payment meters totalled around £250m. Pre-payment meters are most often used by low-income households who find them helpful for budgeting. However, consumer groups are critical of the meters for being overly expensive and complain that suppliers make it difficult for customers to switch. Ofgem today launched a campaign urging households on pre-payment meters to shop around for better deals. Chief executive, Alistair Buchanan, said: “Pre-payment meter customers should take advantage of the competitive market if they are to see further falls in their energy bills.” Four million households are defined as “fuel poor” in the UK because they spend more than 10% of their income on energy. Many of these households use pre-payment meters.