Customers changing energy providers could be in for a shock when their next bill arrives, it has been suggested.
uSwitch said those who switched providers to capitalise on cheap deals could be facing a rise of up to £200 on their heating bills for next year.
The firm made the call after disclosing that seven price guarantee plans will come to an end over the next two months - meaning that householders could be surprised by how much their bills change.
The warning comes months after the big freeze, when drifting snow and bitter cold saw many people wrap up warm and turn the heating dial to full - regardless of the cost.
Figures for the final quarter of 2010 show that output for gas, electric and other utilities providers rose 4.3 per cent.
People threw caution to the wind and kept the heating on amid the freezing weather to trigger the largest jump since 1993.
But when the milder weather took hold in the first quarter of 2011, utilities sector output dropped by 3.5 per cent.