Air Source Heat Pumps: How Many EPC Points and What’s the Real Cost?

If you own rental property with a gas boiler and need to reach EPC Band C before October 2030, an air source heat pump is likely the single most impactful upgrade you can make. No other improvement shifts the SAP calculation as dramatically — and with the £7,500 Boiler Upgrade Scheme (BUS) grant still available, the economics have never been more favourable for landlords.

This guide covers the real-world SAP gains, the true costs after grant funding, which properties are suitable candidates, and how to navigate the installation and reassessment process.

Why heat pumps have the biggest EPC impact

The Standard Assessment Procedure (SAP) — the methodology behind every EPC — heavily weights a property’s primary heating system. When you switch from a gas boiler to an air source heat pump, three things change simultaneously in the SAP model:

• Fuel type shifts from gas to electricity: The SAP calculation uses carbon emission factors for each fuel type. As the electricity grid has decarbonised, the emission factor for electricity has dropped significantly, making electric heating far more favourable in SAP terms than it was a decade ago.
• Efficiency multiplier increases: A modern condensing gas boiler operates at roughly 90% efficiency. An air source heat pump typically achieves a Coefficient of Performance (CoP) of 2.8 to 3.5 — meaning it produces 2.8 to 3.5 units of heat for every unit of electricity consumed. SAP recognises this dramatically higher efficiency.
• Hot water generation improves: If the heat pump also provides domestic hot water (which most do), the SAP gain is compounded because both space heating and water heating calculations benefit.

The net effect is that a heat pump installation can be worth more SAP points than loft insulation, cavity wall insulation and double glazing combined — depending on the property.

Typical SAP point gains

The exact number of SAP points you gain depends on the property type, size, current insulation levels and the existing heating system. Based on industry data and our analysis:

To put that in context: if your property is currently Band D with a SAP score of 58, a heat pump installation alone could push it to 73 or above — comfortably into Band C (which starts at 69). For properties sitting at the lower end of Band D (55–60), a heat pump may be the only realistic single measure that gets you over the line.

The £7,500 BUS grant

The Boiler Upgrade Scheme has been available to landlords since 2022. It provides a £7,500 voucher towards the installation of an air source heat pump, applied as a discount at the point of installation. You do not receive cash — the installer claims the grant directly from Ofgem and deducts it from your invoice.

Key eligibility requirements:

• The property must have a valid EPC (less than 10 years old)
• The EPC must not have outstanding recommendations for loft insulation or cavity wall insulation — if it does, you must install those first
• The property must currently have a fossil fuel heating system (gas, oil or LPG) being replaced
• The installer must be MCS-certified (Microgeneration Certification Scheme)
• The property must not have previously received a BUS voucher

For a complete breakdown of the grant process, eligibility and how to claim, see our dedicated guide: The £7,500 Boiler Upgrade Scheme for Landlords.

Real costs after grant

Let’s look at the numbers honestly. The average cost of an air source heat pump installation in England is approximately £13,200, though this varies significantly by property type and system size:

Crucially, this out-of-pocket spend counts towards the £10,000 cost cap if you are tracking towards an exemption. A medium-system installation at £5,700 after grant effectively uses more than half your cap in one high-impact measure.

Which properties are heat pump candidates?

Not every gas boiler property is an ideal heat pump candidate. The best candidates are:

• Properties with adequate insulation: A heat pump works best in a well-insulated building. If your property has uninsulated solid walls and single glazing, address those first — otherwise the heat pump will be oversized, more expensive to install, and less efficient to run.
• Properties with space for the outdoor unit: An air source heat pump requires an outdoor unit roughly the size of a large washing machine. It needs adequate airflow and should be positioned away from neighbouring windows.
• Properties with a wet radiator system: Heat pumps work with existing radiators, though you may need to upgrade some radiators to larger sizes to compensate for the lower flow temperatures.
• Properties currently on mains gas: The BUS grant specifically targets fossil fuel replacement. If your property has electric storage heaters, it is not eligible.

For broader improvement strategies beyond heat pumps, see our guide on how to improve your rental property’s EPC rating.

Finding an MCS-certified installer

Using an MCS-certified installer is not optional — it is a mandatory requirement for BUS grant eligibility, and it is also the only way to ensure the installation is recognised by the SAP assessor when you commission your new EPC.

To find certified installers:

• Search the MCS website (mcscertified.com) by postcode to find registered installers in your area
• Get at least three quotes — prices vary significantly between installers and there is currently strong demand
• Check that the installer has experience with rental properties and understands the BUS grant application process
• Ask for references from previous landlord clients, not just owner-occupier installations

The installer will handle the BUS grant application through Ofgem’s portal on your behalf. You do not need to apply directly. The voucher is typically issued within three to four weeks and is valid for three months.

The EPC reassessment process

Installing a heat pump does not automatically update your EPC. You must commission a new EPC assessment after the installation is complete. This is a separate process from the installation itself:

• Wait until the installation is fully commissioned and you have the MCS certificate and Building Regulations completion certificate
• Book an accredited Domestic Energy Assessor (DEA) — not the heat pump installer
• Ensure the assessor has access to all documentation: MCS certificate, product data sheets (showing the CoP), and any insulation certificates
• The new EPC will be lodged on the national register, replacing your previous certificate

The new assessment typically costs £60–£120 and takes 45–90 minutes on site. It is well worth doing promptly after installation so you have the improved rating on record.

Check your property’s EPC rating to see your current SAP score, heating type and recommended improvements.