As gas consumption has increased, British gas profits have risen by 31% to £572m for the 12 months to 31 December.
The rise in operating profits compared with £439m from the previous year.
Although December was the warmest on the records, British Gas said that gas usage rose by 5%, as 2015 had more normal temperatures compared with a very mild 2014.
As the wholesale gas prices fell sharply, it left the parent company, Centrica, profits decrease by 12% to 1.46bn.
UK’s largest energy supplier, British Gas, said last week they will be 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 their gas prices by similar amounts.”
After the 57% drop in wholesale gas prices last year, energy suppliers have been under pressure to pass on savings to customers.
However, Centrica’s chief executive, Iain Conn, stressed that the drop in wholesale costs had been passed on to customers and the rise in profit was not because of the fall in commodity.
“The reason the profits went up in 2015 versus 2014 actually is very simple – it’s about the weather and about consumption,” he told the BBC.
“We saw a very mild 2014 and we saw a more normal 2015 and therefore the amount of energy that our customers used went up and therefore the actual total profit went up.”
Since last summer, the competition and markets authority has been conducting a wide-raging investigation into UK’s Energy suppliers.
Between years 2009 and 2013, it estimated that consumers overpaid by £1.2bn.
Ann Robinson, director of consumer policy at uSwitch.com, said: “British Gas has cut standard gas prices three times in the last past year, but it should now go further and reduce electricity bills too.”
Because of other costs make up higher metering costs and government levies. Such as transport and distribution.
Centrica is also a major producer of natural gas oil as well as selling energy through British gas.
“The company wrote down the value of its oil and gas assets and power stations by £2.4bn.”
Those charges contributed to a statutory operating loss of £857m, although that was lower than the £1.137bn for 2014.
Centrica’s shares, have rose 3.7% to 199.5p in early trading on Thursday, they has fallen by a third in the past 12 months.
resulting in a full-year dividend of 12p a share – down from 13.5p for 2014. The company has proposed a final dividend of 8.43p.
Earlier this month, British Gas announced 500 job cuts, mostly in its energy efficiency business.