Energy company SSE Power - which has around 1 million SWALEC customers in Wales - says fuel bills will be cut by around £50 a year on average.
Prices are due to drop from March 24th following a government decision to change green levies.
SSE says it will cost less to supply people with energy in 2014/15 and those on variable tariffs will see their rates cuts by 3.5%.
That means the annual bill for a typical dual fuel customer, averaged across all regions, will come down from £1,224 to £1,174 says SSE.
Unlike some other energy providers SWALEC customers with fixed and capped price tariffs will also have their rates cut by the same amount.
Families in Wales are having to cut down on buying food because they can't afford their energy bills.
That's according to Consumer Futures who says that one in five Welsh households are struggling with fuel bills and three quarters are worried about future costs.
The research also claims that 89,000 households in Wales have fallen behind with fuel payments in the last year.
Shadow Welsh Secretary, Owen Smith, has accused Swalec owner SSE of 'spin' by claiming to have reported a £150m loss. He criticised the energy group for 'selling its own product to itself,' a reference to its wholesale and retail divisions.
The group managing director of SSE's retail business, which owns Swalec, has defended the level of the company's dividend payments to shareholders, while raising prices for consumers.
It comes as the energy giant announces a £115.4m loss in its retail supply business during the six months to 30 September, compared with a £48.3 million operating profit a year earlier.
Will Morris, group managing director of SSE's retail business, said: "Some politicians and media commentators have claimed recently that we value our shareholders more than our customers.
"Or to put it another way, we're focussed on paying them a dividend on their shares, regardless of what that means for our customers.
"Nothing could be further from the truth."
He added: "Without the investment made by shareholders, we couldn't afford to build the infrastructure or buy the equipment needed to deliver what customers need."
Energy giant SSE, which owns Swalec, has revealed it made a loss of £115.4 million in its retail supply business, just weeks after announcing a hike in household bills.
The company insisted it was battling "difficult" energy market conditions.
The group, which has more than nine million customers and is the UK's second largest generator of electricity, blamed the performance on rising costs of wholesale energy, environmental and social policies and distribution.
Its overall underlying group profits fell 11.7% to £354 million in the six months to September 30.
The first half loss in its retail supply arm compares with a £48.3 million operating profit a year earlier.
SSE was the first of the major suppliers to announce a tariff rise, saying last month that it would lift prices by an average of 8.2% from Friday.