Energy firm E.On will raise prices for dual fuel customers by 8.7% on 18 January, the company has said.
All of the major energy providers have now announced price rises this winter for UK domestic customers.
However, price changes might differ depending on where residents live in the country.
E.On had pledged that it would not change prices before the end of 2012, which prevented any announcement before the start of December.
Those who have just electricity supplied by E.On will see a price rise of 7.7%, but gas-only customers will see prices go up by an average of 9.4%.
"We have held back from increasing our prices for as long as we possibly could and at the same time have worked hard to reduce our own costs as a business so that our customers can get the best price possible," said Tony Cocker, E.On chief executive.
E.On dual fuel customers will see their bill rise by just over £100 a year on average as a result of the imminent price rise.
E.On customers were hit by an 18% gas price rise and an 11% electricity price rise in late 2011, although there was also a price cut for the latter of 6% early in 2012.
Customers would be sent a letter, Mr Cocker said, explaining the reasons for the latest price increases.