Profits at British Gas have risen by 31% to £574m for the 12 months to 31 December as gas consumption increased.
The rise in operating profits compared with £439m for the previous year.
British Gas said
gas usage rose by 5% despite the warmest December on record, as 2015
had more normal temperatures compared with a very mild 2014.
However, profits at its parent company, Centrica, fell by 12% to £1.46bn as wholesale gas prices fell sharply.
Last week British Gas - the UK's largest energy supplier - said it was cutting gas prices by 5.1%, the last of the big six energy suppliers to do so.
E.On, EDF, SSE, Scottish Power and Npower have all cut gas prices by similar amounts.