One in three bills are wrong

One in three households have been billed incorrectly by their energy company in the past two years, prompting consumers to vote energy suppliers as the worst culprits for inaccuracy.

Not only have customers had to deal with inaccurate billing based on estimates, but they have then had to sort the matter out with their supplier. On average this takes two months, according to a survey conducted by price-comparison site uSwitch.com

Meanwhile, four out of 10 customers are overcharged and are owed money. A quarter of consumers are not paying enough and are slipping into the red.

Npower has been the worst culprit for inaccurate billing. Queries about the firm to Energywatch, the consumer watchdog, have grown by 21 per cent in the past year. Npower, in response, has invested an extra £2m in customer services.

Ann Robinson of uSwitch.com said: "I suspect suppliers will be haunted by this reputation for inaccurate bills until smart meters lay that ghost to rest – but that won't be for many years."

All suppliers are involved in smart-meter trials and E.ON is piloting the technology as part of a two-year, £12m investment.