The scheme had a budget of £150m to fund 30,000 heat pump installations in its first year.
But latest figures released by regulator Ofgem show that in the first 12 months under 10,000 households received their £5000 subsidy voucher.
That means £90m of unspent budget will now be returned to the Treasury.
The scheme has another two years to run with £300m allocated over the period to drive the fitting of heat pumps.
Mike Foster CEO of the trade body the Energy and Utilities Alliance, said: “It takes a certain type of genius to fail to give away £150m of taxpayers’ money and this wretched scheme looks like it has done just that.
“When will the Government actually listen to the people, the majority of whom simply cannot afford a heat pump, subsidised or not.”
He added: “There was a time when a Conservative Government took pride in being fiscally prudent with taxpayers’ money. Now they just ladle out the cash on a green spending spree.
“What makes this profligacy even worse is that insulation measures could save more carbon, keep bills down and provide a sound economic investment for the Treasury.”
Last month The House of Lords’ Environment and Climate Change Committee called for an urgent overhaul of the BUS in order to expand uptake and to improve public awareness of the incentive.
It recommended rethinking the level of assistance provided to lower income homes that would be unable to install a heat pump even with the grant funding offered.
The committee also warned about the urgent need for upskilling and expanding the installer base to ensure heat pumps are being effectively run in different property types.