The House of Commons Library has published a stark assessment of Britain’s housing stock: roughly a third of homes are still rated EPC D or below. That is not a footnote in a policy paper, it is a direct drain on household budgets and a drag on the UK’s net-zero timeline.
As reported by The House of Commons Library, the data confirms what anyone who has stood in a draughty Victorian terrace already knows: the fabric of our homes is failing us. The UK has some of the oldest and leakiest housing stock in Europe, and the gap between the best and worst performing homes is widening.
What EPC D or below means for your bill
An EPC rating of D or below translates directly into higher energy costs. For a typical 3-bed semi using 12,000 kWh of gas and 2,900 kWh of electricity per year, moving from an EPC D to a C can save around £300 annually. Going from an F to a C can save more than £1,000. Those are not theoretical figures, they are based on standard assumptions used by the Energy Saving Trust and Ofgem.
The catch is that most households in the D-or-below bracket are on standard variable tariffs, which means they are already paying more per unit than those on fixed deals. The price cap will rise again in October 2025, adding roughly £63 to the average bill. For an EPC F home, that increase is proportionally larger because more energy is wasted.
Who qualifies for help, and who doesn’t
The Great British Insulation Scheme and the Boiler Upgrade Scheme are the two main government programmes currently open. The former targets low-income households and those in the least efficient homes (EPC D or below) with free or heavily subsidised loft and cavity wall insulation. The latter offers a £7,500 grant toward an air-source heat pump, but only if your home has an EPC C or above, which excludes the very homes that need it most.
This is a policy contradiction. The homes that would benefit most from a heat pump are the ones that cannot get the grant because their fabric is too leaky. The government’s own analysis, cited by the House of Commons Library, acknowledges that upgrading the building envelope first is essential. Yet the grant criteria have not been adjusted.
What it costs to fix, and what it saves
Retrofitting a typical 3-bed semi from EPC D to C costs somewhere between £5,000 and £15,000 depending on the measures needed: loft insulation (£500–£1,000), cavity wall insulation (£1,000–£2,500), solid wall insulation (£8,000–£15,000), and double glazing (£4,000–£8,000 for a full set). The payback period varies. Loft insulation pays for itself in under two years. Solid wall insulation can take 10–15 years.
But the calculation changes when you factor in rising energy prices and the value added to the property. Estate agents and surveys consistently show that homes with EPC C or above sell for 5–10% more than equivalent D-rated properties. That is a real return, not a hypothetical one.
What to do next
If your home is EPC D or below, start with the cheapest, fastest measures: loft insulation, draught-proofing, and a smart thermostat. Check eligibility for the Great British Insulation Scheme on gov.uk. If your home is already C or above, the Boiler Upgrade Scheme is open until 2028, but book an installer now because demand is high. The deadline for the current phase of the scheme is 31 March 2027.
The House of Commons Library has laid out the problem in black and white. The solution is not a mystery. It is a matter of who acts first, and how quickly.
Frequently Asked Questions
Loft insulation and draught-proofing are the most cost-effective measures. Loft insulation typically costs £500–£1,000 and can pay for itself within two years through lower bills. Draught-proofing windows and doors costs under £200 and can save around £60 a year.
Not under the current Boiler Upgrade Scheme, which requires an EPC C or above. However, if you first upgrade your insulation and achieve a C rating, you can then apply for the £7,500 grant. Some installers may offer alternative funding, but the government grant is the most generous option.
