Families moving into brand new government-funded homes are facing electricity bills up to four times the amount they believed they would pay, an investigation has found.
The properties, built under affordable housing schemes, were issued with Energy Performance Certificates that estimated annual costs of between £400 and £500 for heating and hot water.
But according to research by BBC One's Rip Off Britain, hundreds of families have had to pay treble or quadruple that amount.
The problem is being blamed on a heating system that some estates are now replacing, the programme said. Called an exhaust air source heat pump, the system works by taking the heat from waste air leaving the property and pumping it back into the home to provide heating and hot water.
Swedish manufacturers NIBE claim it is both effective and economic and replaces the need for a gas boiler. But after surveying the system, which is thought to be in 15,000 UK homes, an independent heating expert told the programme he does not believe the main pump is big enough to heat most UK homes.
Instead, he said it relies on its extremely costly back up electric immersion heater - leading to higher bills.
Sam Claussen, who lives on an estate in St Neots, ended up owing £1,500 to her energy supplier - an amount she could not pay. She said: "It became absolutely clear that this system was far from economical and was in fact costing us a fortune to run. Over Christmas it very quickly became £10 a day, and I was horrified."
Ms Claussen's housing association has paid over £45,000 to help tenants with their unexpectedly high bills and are taking steps to remove the system from all the homes on the estate. The investigation found residents on a further 13 estates across the UK were reporting the same problem
NIBE told researchers the problems were almost always due "to poor specification, installation or maintenance, and not the systems themselves". The company said it never sold the system "on the basis of cost" and that independent research demonstrates the efficiency and effectiveness of the system in the UK.
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