Almost four million UK households are in debt to their energy provider, owing an average of £128 per home, according to a uSwitch survey.
Despite the mild winter, 14% of the households which owe money have seen their debt increase by £5 on last year, following a series of price hikes, the energy comparison company said.
The average household energy bill is now £1,265 a year, £53 more than a year ago and £793 or 168% higher than in 2004.
A third of those in debt owe more than they did a year ago while 9% owe less, the survey found.
Ann Robinson, uSwitch director of consumer policy, said: "The average household energy bill is £53 a year dearer than a year ago. For many consumers, the only thing that has kept this particular wolf from the door is the fact that this winter has been exceptionally mild."
More top news
A remarkably mild night with misty low cloud on the hills of Scotland, Wales and north-west England and further rain in places.
The former head of the Diplomatic Service breaks down the hidden meanings behind Theresa May's letter to Donald Tusk
The storms that struck Texas and Oklahoma late on Tuesday brought tornadoes, tennis ball-sized hail and powerful winds.