Britain's bitterly cold winter boosted the profits of British Gas owner Centrica after the company raised tariffs by 6% in December.
The rise in profits, from £345 million in the same period last year, is likely to spark anger despite the company pledging to halt further tariff hikes.
Campaigners have called for the company to go further and cut prices.
Centrica chief executive Sam Laidlaw said: "With our customers using more gas to stay warm during the unusually cold winter, we're doing everything we can to help them keep their energy costs under control and make bills simpler and clearer."
More top news
Tonight a band of cloud and rain will spread into Scotland and Northern Ireland.
Greenpeace has obtained leaked documents which reveal how much the US has been pushing the EU on the TTIP trade agreement.
Appeals court clears the way for case against U.S. Army Sergeant and former Taliban prisoner Bowe Bergdahl to resume.