The owner of SWALEC, SSE, is to freeze household gas and electricity prices.
The group is also carrying out a "legal separation" of its wholesale arm - which includes energy production and storage - from its retail division which sells energy to homes and businesses.
The announcements come as SSE says it's shedding 500 jobs as part of a cost-cutting programme.
The Shadow Welsh Secretary says energy bills in Wales will still rise despite UK Government action to bring them down. During Wales Questions in the Commons, Owen Smith described as 'a con-trick' a cut of £50 a year announced by SSE which owens SWALEC.
He said that reduction wouldn't offset previously announced increases which would mean that Welsh families would still pay higher bills. He added later that,
It is a con-trick for SSE to claim, as their press release this morning does, that the company is cutting its prices. The small reduction being offered only slightly offsets the 8.2% price hike that a million SWALEC customers were hit with in November. The reality is that even after the Government’s changes to green levies, the average household will still be paying £70 more for their energy than last winter.
Wales has the highest gas and electricity bills of anywhere in the UK, yet our biggest energy provider made £350 million profit last year, allowing it to give inflation-busting pay-outs to shareholders and pay its Chief Executive £755,000, while customers struggle to make ends meet.
It can only do this because it operates in a broken market and the only long-term solution is to reform the market so that customers are no longer ripped off. But we also need a short-term answer to sky-high prices which is why Labour would freeze prices for 20 months while we bring in these reforms.
Wales Office Minister Stephen Crabb rejected the accusation and described Labour's price freeze as a proposal which 'has no credibility.'
What we are doing is real practical action that helps families at difficult times and the picture we are seeing in Wales overall is positive.
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.
No matter how hard SSE spin by highlighting a £150m loss in its retail arm, the reality is the company’s overall profit came in at around £350m. The attempt to plead poverty will fall on deaf ears in Wales, where we already have the highest energy bills of anywhere in the UK.
SSE’s profits of £350m have allowed it to give shareholders inflation-busting pay-outs while customers face inflation-busting price hikes. It can only do this because it operates in a flawed market. The group sells its own product to itself and hasn’t got enough serious competition.
A long-term solution is to reform the energy market, which a Labour Government will tackle head on. But we also need a short-term answer to sky-high prices. That’s why Labour is calling on David Cameron to freeze energy prices and address the cost of living crisis facing families across the country.
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.
Shadow Welsh Secretary Owen Smith has sharply criticised the decision by SSE to increase energy prices.
Families in Wales are being particularly hard hit by this increase.
Wales – where there are more than one million SSE customers - already suffers from the highest energy bills and lowest levels of disposable income of anywhere in Britain.
This is nothing more than an act of gross profiteering. People in Wales are clearly being ripped off by this energy company and it needs to stop.
People are already suffering under David Cameron's cost of living crisis and now, thanks to his failure to stand up to the big energy companies, consumers will be hit by ever high bills, with SSE increasing prices by nearly 10%. This is a sign that David Cameron only stands up for the privileged few.
If ever there was proof that Ed Miliband was right and we need a freeze on energy prices, this is it.
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Labour Leader, Ed Milliband, has taken to Twitter to criticise the announcement that SSE, which owns energy supplier SWALEC, will increase its prices by 8.2% from next month.
With so many households already in fuel poverty, how can they justify more prise rises? People just cant afford to pay anymore!
It's the old I feel sorry for as how many become seriously ill over the winter as they cant afford turn the heating on as gas suppliers keep putting prices up.
I was expecting a rise, after all the cold weather is here, so it hasn't come as a surprise at all.
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Utility giant SSE, which owns Welsh energy supplier SWALEC, has announced prices will rise by 8.2 per cent from 15 November.
SSE has around 600,000 electric customers, and 400,000 gas customers in Wales.