Replacing millions of gas and electric boilers with controversial heat pumps would cost taxpayers £115bn, a new report has warned.

The Government has repeatedly suggested households replace traditional boilers with heat pumps to reduce carbon emissions and has allocated £450m to its new Boiler Upgrade Scheme. However, this scheme will only allow around 90,000 households to replace their boilers.

Extending the scheme in its current form to all homes on the gas grid would cost the public purse £115bn, the TaxPayers’ Alliance has said. 

The scheme is designed to subsidise homeowners to install low-carbon heating systems – such as heat pumps – by mitigating the cost of installation, bringing the cost closer to that of installing a new gas boiler. However the high upfront costs of the devices means few ordinary households will be able to take advantage of the scheme.

So-called “air source” heat pumps can cost around £10,000 to purchase and install, according to the Eco Experts, an advice site. Even with the grant households would have to spend £5,000 to upgrade, compared to £2,000 to £4,000 for a new gas boiler, according to Checkatrade. 

Heat pumps, which draw heat from the ground or the air, have proven controversial. As well as the cost, there are doubts these systems work efficiently in cold countries like Britain. The machines have also been criticised for the noise generated when running.

Craig Mackinlay, Conservative MP for South Thanet, said the cost was too high for many households. “Spending billions on a technology that clearly isn’t ready is not the right focus for the Government,” he said.

“This money will almost certainly go to the wealthiest households at a time when our primary focus should be on getting bills down for the many. If there’s money available, a wider programme of home insulation would be a better plan and could achieve more in the way of emissions reductions.”