WELSH households face the misery of being hit by more than £100 extra on their energy bills by the end of the year – on top of the £140 hike they have already faced since Christmas.
The price rises predicted by experts will come as a hammer blow to pensioners and others on low incomes.
The news comes just weeks after energy industry bodies refused to appear before an Assembly committee to explain why customers in Wales pay higher prices than in England.
Welsh householders pay on average 10 per cent more for power than their counterparts in England.
Many in Wales are already being hit hard by rising food, transport and petrol costs amid widespread concern over the economy.
The pain will be increased by the likelihood of increases this autumn, just as householders switch on the heating.
The average annual bill in Wales has gone up by around £140 since December, but the price energy companies pay for gas and electricity has soared by a further 26 per cent since then.
This is likely to be passed on to households later this year, with experts predicting a further 10 per cent rise to the average family’s annual energy bill – taking it to more than £1,200.
Joe Malinowski of The Energyshop, a comparison website, said that, as the rise in cost for householders had not kept up with the rise in wholesale prices, consumers were “looking at further increases and misery throughout 2008”.
He added: “The price of energy is going to be very high this winter and people are going to need to be well prepared for the bills coming through their doors at the beginning of next year.”
Energy companies set their prices lower for some households than for others, with direct debit payers and those who manage their bills online paying around £200 a year less than those who do not.
Mr Malinowski recommended: “Unless you take these two measures you are almost destined to pay four-figure sums for your energy this year.”
Households in South Wales who pay for electricity by direct debit are charged an average of £409 a year, compared to just £379 on average across Great Britain.
Welsh families who use pre-payment meters face an even stiffer financial penalty. Those in South Wales pay an average of £448, compared to £411.
Historically, suppliers have blamed the higher prices on problems of distribution over certain areas of Wales.
According to the website The Energyshop, Npower is the most expensive company for those paying their bills by direct debit while Scottish Power, which distributes electricity in North Wales, is costliest for householders paying by cash or cheque.
Those using a pre-payment meter pay even more, although earlier this month Chancellor Alistair Darling said the UK Government would push energy companies to reduce bills for those using meters.