Energy supplier E.ON is to increase prices by 3.7% for average dual fuel bill (an extra £48) and gas by 4.6% (£37) from January 18.
The Co-operative Energy firm has announced a price rise of 2.5% on average.
In an email to customers, the company said: "As winter sets in and some energy companies raise their prices by as much as 10%, we’ve got some good news for you to warm to.
"Co-operative Energy is raising its prices on 8 January…but only by 2.5% on average across all our customers."
Energy Secretary Edward Davey called E.ON's price rises announcement "disappointing news".
Bur Mr Davey stressed:
This rise is ... lower than it would have been as a result of Government action to reduce the impact of price rises on consumers.
As part of their announcement today, E.ON have confirmed they will pass on these savings to their customers.
This does not let energy companies off the hook.
Asked about the timing of E.ON's price rises announcement, which came amid media focus on the death of Nelson Mandela and the devastating storms across the UK, Downing Street said, "It is for them to explain their decisions."
E.ON has announced its customers' dual fuel energy bills will increase by an average of 3.7% from January 18.
The company said that means the average variable dual fuel bill will go up by £48, electricity only prices will increase by 3.7% or £20, and gas only bills will climb by 4.6% or £37.
Chief executive Tony Cocker said changes announced by the Government earlier this week reduced the overall level of the rise that was necessary to cover extra costs.
The energy firm said it was "working hard to limit the impact on its customers" by announcing a lower average percentage rise than any other major supplier.
Earlier this week, E.ON said it did not expect to have to raise prices in the next 18 months "as a result of social or environment obligations".
But E.ON also warned, "There remains a risk, however, that increases in network charges or wholesale energy costs for example could force a price increase".
The announcement followed the Government's shake-up of green levies on Monday.
Read: E.ON 'does not expect to raise prices in the next 18 months'
Energy supplier E.ON will increase prices by an average of 3.7% from January 18.