The Treasury is weighing cuts to home insulation and heat pump funding. The Chancellor has received an open letter from more than 300 green businesses, manufacturers, installers, energy companies, warning that such a move would be a catastrophic own goal for household bills and net zero. This is not a theoretical debate. It is about whether the UK finally tackles the worst housing stock in western Europe, or leaves millions of homes leaking heat for another decade.
As reported by E3G, the letter specifically warns against cutting programmes that fund cavity wall insulation, loft insulation, and heat pump installations, the very measures that reduce energy bills and improve EPC ratings. The timing is brutal: energy prices remain high, the Great British Insulation Scheme is only halfway through its 2027 window, and the Boiler Upgrade Scheme has finally started to gain traction with homeowners.
Who qualifies, and who doesn’t
The two main grants at risk are the Great British Insulation Scheme (GBIS) and the Boiler Upgrade Scheme (BUS). The Great British Insulation Scheme closed on 31 March 2026. It funded insulation measures only and never covered windows or glazing. The BUS offers £7,500 off an air-source heat pump for any home in England and Wales, regardless of income.
But the letter from businesses, including Kingspan, Worcester Bosch, and Octopus Energy, argues that both schemes need long-term certainty to build supply chains and train installers. Without it, the UK will repeat the pattern of the 2010s: stop-start funding that destroys installer confidence and leaves homeowners stranded with half-finished work or no options at all.
Ofgem data shows GBIS had installed measures in only about 150,000 homes by mid-2024, far short of the 300,000 target. The BUS has been more successful, with applications rising 45% in 2024, but the Treasury could still cap or reduce the grant value.
What it costs a typical 3-bed semi
For a 3-bed semi-detached house with an EPC rating of D, the Energy Saving Trust estimates that cavity wall insulation saves around £300 a year, loft insulation saves another £200, and a heat pump can cut heating costs by 20-30% compared to an old gas boiler. Without grants, cavity wall insulation costs roughly £500-1,000 and a heat pump installation £10,000-15,000.
The catch is that the Treasury sees these as upfront costs to the taxpayer, not long-term savings to households. That is a false economy. Every pound spent on insulation reduces the UK’s gas import bill, lowers carbon emissions, and cuts pressure on the NHS from cold homes. The businesses’ letter makes this point explicitly: retrofit creates jobs, reduces fuel poverty, and boosts local economies.
What homeowners should do now
The letter does not guarantee the Chancellor will listen. But it signals that the industry is united and watching. For homeowners, the safest move is to apply for grants while they exist. GBIS and BUS both require an accredited installer; you can find one through the Microgeneration Certification Scheme (MCS) database or the Energy Saving Trust’s local installer search.
The Great British Insulation Scheme closed on 31 March 2026. It funded insulation measures only and never covered windows or glazing. If you have a home with an EPC rating of D or lower, or you are replacing an old gas boiler, start the process now. A full home energy assessment from a certified assessor costs about £100-200 and will tell you exactly which grants apply. That £200 could unlock thousands in savings.
Do not wait for a government press release. The businesses have done their part. Now it is up to you to claim what is available before the Treasury decides otherwise.
Frequently Asked Questions
For a typical 3-bed semi-detached house, cavity wall insulation costs between £500 and £1,000 without grants. The Great British Insulation Scheme closed on 31 March 2026. It funded insulation measures only and never covered windows or glazing.
The Boiler Upgrade Scheme offers £7,500 off an air-source heat pump installation for any home in England and Wales, regardless of income. This reduces the typical cost from £10,000-15,000 to around £2,500-7,500, and can cut heating costs by 20-30% compared to an old gas boiler.
The scheme covers cavity wall, loft, and solid wall insulation, but funding is uncertain as the Treasury considers cuts, only about 150,000 homes had been upgraded by mid-2024 against a 300,000 target.
The Treasury is weighing cuts to the Great British Insulation Scheme and Boiler Upgrade Scheme, but over 300 green businesses including Kingspan and Octopus Energy have warned this would be a 'catastrophic own goal' for bills and net zero. No final decision has been made, but homeowners should apply for grants now while they exist.
Loft insulation saves around £200 a year for a typical 3-bed semi-detached house with an EPC rating of D. The Great British Insulation Scheme closed on 31 March 2026. It funded insulation measures only and never covered windows or glazing.
