Npower became the latest energy supplier to cut prices when it announced a 5 per cent fall in gas tariffs today.
The big-six supplier said prices for standard and capped gas charges will fall from February 1, while it will also waive cancellation fees on fixed-price deals for the next two months to allow customers to switch tariffs and take advantage of the price drop.
The German-owned company has become the fourth supplier to announce energy price cuts this week. British Gas cut bills for more than five million customers by making an instant average cut of 5% in its standard electricity tariff.
Southern Electric and Swalec owner SSE said it would cut the price of household gas by 4.5% from March 26, while French-owned rival EDF cut gas prices by 5% from February 7. Other operators are expected to follow suit.
Although four of the big six suppliers have announced cuts, none has reduced both gas and electricity prices.
All six put prices up in recent months following increases last winter, blaming rising wholesale costs, and there have been loud calls for cuts after recent falls in wholesale prices.
Paul Massara, chief commercial officer at RWE Npower, said: "It's obviously no coincidence that several energy companies have announced price reductions this week and we do not apologise for joining them.
"We are now at a point where costs, at least in the short term, can justify a price cut and we want to make sure that npower customers always get competitive deals."
Npower said the cut would come in soon enough to "get a real benefit before the spring".
The reduction will reduce the average annual dual fuel bill by £39 to £1,149.
Adam Scorer, director of policy and external affairs at Consumer Focus, said: "These cuts will not compensate for the big rises in 2011, they will not transform the energy market or significantly lessen the burden on hard-pressed consumers.
"Scottish Power and E.ON customers will expect to see their suppliers rapidly follow suit given the speed from other suppliers.
"If companies are more prepared to cut prices quickly when wholesale markets allow, if they fully embrace Ofgem's market reforms and they mean what they say about earning consumer trust, then the rehabilitation of energy companies may be possible. But there's a long road to travel first."