The average heat pump runs at £1,100–£1,800/year in a poorly insulated UK home, here is what that means for your bills
If your home has uninsulated cavity walls, single-glazed windows, or no loft insulation, you are likely wondering whether a heat pump is a realistic option. The short answer is that it can work, but the running costs will be higher than in a well-insulated property.
Energy Saving Trust data shows that a heat pump in a poorly insulated three-bedroom semi-detached home typically costs between £1,100 and £1,800 per year to run (Energy Saving Trust, 2026). By comparison, a gas boiler in the same property would cost around £900–£1,200 annually. The gap narrows if you have a time-of-use electricity tariff that offers cheaper overnight rates.
Actual running costs depend on three main factors: the size of your property, the heat pump’s Seasonal Coefficient of Performance (SCOP), and your electricity tariff. A higher SCOP means lower running costs. The £7,500 Boiler Upgrade Scheme (BUS) grant remains available in 2026 and can reduce the upfront installation cost significantly (GOV.UK, 2026).
Quick numbers heat pump performance and grant eligibility in a poorly insulated home
| Metric | Poorly insulated home (estimated) | Well-insulated home (reference) | Source |
|---|---|---|---|
| Annual running cost (£) | £1,100–£1,800 | £600–£900 | Energy Saving Trust, 2026 |
| System efficiency (SCOP) | 2.5–3.0 | 3.5–4.5 | MCS, 2026 |
| Grant eligibility (BUS) | Eligible | Eligible | GOV.UK, 2026 |
| Minimum EPC rating required for BUS | No minimum | No minimum | Ofgem, 2026 |
| Typical heat loss (kW) for a 3-bed semi | 10–14 kW | 5–8 kW | BRE, 2026 |
You do not need an EPC Band C to get a heat pump grant
The Boiler Upgrade Scheme does not require a minimum Energy Performance Certificate (EPC) rating for your property in 2026 (GOV.UK, 2026). This is a common misconception. However, the installer must be MCS-certified and must complete a room-by-room heat loss calculation before installation.
If the calculated heat loss exceeds what the heat pump can deliver, the installer may refuse to proceed or recommend insulation upgrades first. The Great British Insulation Scheme closed on 31 March 2026. It funded insulation measures only and never covered windows or glazing.
The direct answer a heat pump can work in a poorly insulated UK home, but you will likely need a larger unit and higher flow temperatures
Yes, a heat pump can heat a poorly insulated home, but it will run at lower efficiency and higher cost than in a well-insulated property. The SCOP in a poorly insulated home typically falls to 2.5–3.0, compared to 3.5 or higher in a well-insulated home (Energy Saving Trust, 2026).
To compensate for higher heat loss, the installer may specify larger radiators or underfloor heating to operate at lower flow temperatures, as required by the MCS 022 standard (MCS, 2026). The heat loss calculation will determine the required heat pump output in kilowatts and whether your existing pipework can handle the flow rate.
What size heat pump do I need?
How to check if your property qualifies for a heat pump grant in 2026 (even with poor insulation)
Three key eligibility steps apply for the Boiler Upgrade Scheme. First, your property must be in England or Wales. Second, the installer must be MCS-certified. Third, your existing fossil-fuel heating system must be removed and replaced (GOV.UK, 2026).
The grant is applied by the installer, not by you. You choose an MCS-registered firm, and they deduct the £7,500 from your quote. A valid EPC is not required for BUS eligibility, though the installer may request one to help assess heat loss. Be aware that some installers may decline to quote if the property has no loft insulation or single glazing, as the system may not meet their performance guarantees.
The one certification you must check before hiring an installer
MCS (Microgeneration Certification Scheme) certification is mandatory for any installer claiming the Boiler Upgrade Scheme grant (GOV.UK, 2026). TrustMark covers customer protection but does not replace MCS for grant eligibility. Gas Safe Register is irrelevant for heat pumps; installers should be MCS-certified and also registered with NICEIC or NAPIT for electrical work (NICEIC, 2026).
To verify a company’s certification, use the MCS online installer database at mcscertified.com before signing any contract. This is the only way to guarantee you can claim the grant.
How to find a reliable heat pump installer
What happens if your home has no loft insulation or cavity wall insulation
You can still get a heat pump, but the installer’s heat loss calculation will likely flag a need for insulation upgrades first. Under the ECO4 scheme, low-income households may qualify for free insulation before a heat pump installation (Ofgem ECO4 guidance, 2026). The Great British Insulation Scheme closed on 31 March 2026. It funded insulation measures only and never covered windows or glazing.
While you can proceed without insulation, you will face higher running costs and may void any performance warranty offered by the installer. In practice, most MCS-certified installers will recommend addressing the worst insulation gaps before committing to a heat pump installation.
Frequently Asked Questions
Yes, a heat pump can work in a poorly insulated home. Energy Saving Trust data shows running costs of £1,100–£1,800 per year for a 3-bed semi, higher than in a well-insulated home.
The running cost is typically £1,100–£1,800 per year for a 3-bed semi-detached house with poor insulation, according to the Energy Saving Trust (2026). This compares to £900–£1,200 for a gas boiler.
No, you do not need a minimum EPC rating to get the Boiler Upgrade Scheme grant in 2026 (GOV.UK). The installer must be MCS-certified and carry out a heat loss calculation.
A heat pump costs £1,100–£1,800 per year to run, while a gas boiler costs £900–£1,200 in the same poorly insulated 3-bed semi (Energy Saving Trust, 2026). The gap can shrink with a time-of-use electricity tariff.
The Seasonal Coefficient of Performance (SCOP) for a heat pump in a poorly insulated home is typically 2.5–3.0, compared to 3.5–4.5 in a well-insulated home (MCS, 2026). A higher SCOP means lower running costs.
Yes, the Boiler Upgrade Scheme is available for poorly insulated homes in 2026 (GOV.UK). There is no minimum EPC rating required, but the installer must confirm the system can heat your home.
