Families could be paying nearly £5,000 a year for their energy by 2020, partly due to the government’s billion-pound investment programme, a report warned today.

The average bill could soar to £4,733 a year, nearly four times higher than the £1,243 paid now, according to research by comparison firm Uswitch.

The firm extrapolated current trends in energy prices, which have seen energy bills more than double over the past five years from an average of £580. If that level of increase continues, bills will hit £4,185 a year by 2020.

An £234 billion bill to cover investment in Britain’s energy supplies over the next 15 years would add another £548 a year to household bills – giving a total bill of £4,733.

The figures are likely to provoke anger among consumers because energy giants have been accused of withholding falls in the wholesale price of gas earlier this year. Wholesale energy prices have fallen by more than 50 per cent since their peak in the autumn of last year, according to Theenergyshop.com, another comparison site. In contrast, domestic energy bills have been cut by about 5 per cent this year.

Analysts suggest a further 10 to 15 per cent cut would be justified, but the recent rise in the price of oil to more than $70 a barrel could prevent further cuts.

Ann Robinson, director of consumer policy at USwitch.com, said: “This is a wake-up call for us all. The £5,000 a year energy bill may seem like an outside possibility, but we have to remember that energy bills doubled in the past five years alone and that the huge investment needed just to keep the lights on in Britain will alone add £548 a year onto our bills. The fact is we are entering a new era of high cost energy and households will have to adapt their behaviour accordingly.”

The £234 billion promise of investment in energy over the next 15 years includes £112.5 billion on renewable energy generation, £52 billion on power plants, and £40 billion on upgrading the network, including gas storage. Another £13 billion will be spent on the roll-out of smart meters and £16 billion on reducing carbon emissions.