British Gas has announced a 5% cut in its electricity prices with immediate effect.
The move comes a day after EDF Energy announced plans to cut its gas tariff by the same percentage owing to low energy use during the mild winter.
The price cut will add pressure on the other major suppliers to cut their tariffs owing to the fall in wholesale prices.
British Gas said the average annual domestic bill would fall by £24.
"We want to keep prices as low as possible for our customers. Household budgets are stretched, and we are doing everything we can to help our customers keep their bills down," said Ian Peters of British Gas.
"This price reduction means British Gas is once again offering the cheapest standard electricity, on average, of any major supplier."
The price cut comes after a 16% rise in electricity prices and an 18% rise in gas prices for British Gas customers in August.
The company said that 5.3 million customers on variable tariffs, including those on dual-fuel deals, would benefit from the price cut.
The reduction comes into effect ahead of the EDF gas price cut which comes into force on 7 February. The EDF change is set to cut the typical annual bill by £38.
British Gas said that it was not changing its gas charges because, although there had been some short-term falls in the cost of gas, the longer term trend in wholesale prices was upward. It said it bought its energy in advance.
The company said it was too early to predict what would happen to prices in the future.