Energy customers on standard tariffs could be facing average quarterly bills of £530 in coming months following a spate of price rises coinciding with the start of winter.
Consumers typically use around 40% of their annual energy consumption during the winter months, according to a study by MoneySupermarket.com, with the next average quarterly standard bill likely to hit well over £500.
The major providers announced price rises averaging 7.6% between August and December, with these coming into effect between October 15 and January 18.
MoneySupermarket.com consumer finance spokeswoman Clare Francis said: "Many households will be dealing with a festive financial hangover this January so a huge energy bill will come as an unwelcome shock.
"A spate of price rises which mostly came into effect before the Christmas period saw the cost of energy increase by an average of 7.6%, leaving many people worrying about the crippling costs they could face in the coming months."
She urged consumers to consider moving onto a cheaper tariff, and also reminded those on fixed deals to be aware of when these ended.
She said: "Those languishing on their provider's standard energy product should take action as quickly as possible. The typical saving they could make by moving to the best value fixed deal is £1,734. This saving would go some way to offset their costly winter bills, and by fixing their energy, they can safeguard against any future price rises over the term of the deal and ensure they don't face the same bill shock after Christmas 2013.
"There are also simple things you can do to reduce the amount of energy you use at home. Turning your heating down by one degree, doing your washing at 30 degrees rather than 40 or 60, taking a shower rather than a bath will all reduce your energy consumption and collectively over the course of the year could save you a significant amount of money."
She added: "Many people have done the right thing and moved onto fixed energy tariffs to protect themselves from future price hikes. However, it's really important to remember to switch again when their current fixed deal ends. Otherwise they'll probably be transferred onto their provider's standard price plan which could result in their annual energy costs leaping by more than £300.
"Energy bills only ever seem to be on the up so I recommend taking a fixed deal for peace of mind and not having to worry about price rises if they are announced."