UK billpayers could see energy bills rise by up to £63 million as 57 fixed deals from 16 suppliers finish at the end of November and they are automatically moved onto more expensive standard variable tariffs.
Comparison and switching service Uswitch warns 816,000 households could be affected and suggests they will potentially see their bills rise by an average of £155.
The firm highlights consumers can switch now to avoid this hike in prices.
Sarah Broomfield, Energy Expert at Uswitch, said: “Customers often get caught out when their fixed energy plan ends and they are moved automatically onto a standard variable tariff that ends up costing them more money.
“This is a particularly busy time of year with Christmas on the way, and it’s easy to forget to change supplier — but not switching could come with a hefty £155 price tag attached.
“No one should be paying more than they need to for their energy, and as we head deep into winter, now is the time to check when your deal is coming to an end.”