How a Heat Pump Affects Your EPC Rating
A heat pump almost always improves an EPC rating, but by how much depends on your property. Here is how the SAP assessment works and what to realistically expect.
A heat pump almost always improves an EPC rating, but the size of the improvement varies significantly depending on the property type, the previous heating system, and the flow temperature the heat pump is designed to operate at. Understanding how the EPC assessment works — and what specifically a heat pump changes in the calculation — helps set realistic expectations before installation.
How EPCs are calculated
EPC ratings are produced using SAP (Standard Assessment Procedure), a methodology defined by DESNZ and currently at version SAP 10.2. SAP calculates the energy efficiency of a dwelling based on its construction, insulation levels, heating system, hot water system, lighting, and ventilation. The output is an energy efficiency score from 1 to 100, which corresponds to EPC bands G (1–20) through A (92–100).
The SAP score incorporates both the energy consumption of the heating system and the carbon emissions associated with that energy source. Under SAP 10.2, electricity has a carbon factor of approximately 136 gCO₂/kWh, significantly lower than gas (215 gCO₂/kWh). This means switching from gas to electric heating — including heat pumps — improves the carbon score component of the EPC, even before the efficiency advantage of the heat pump is considered.
What a heat pump changes in the SAP calculation
When an EPC assessor updates a property's assessment following a heat pump installation, the changes to the SAP calculation include:
- •Heating fuel type changes from gas/oil/LPG to electricity — lower carbon factor
- •Heating system efficiency changes from approximately 90% (condensing boiler) to the heat pump's SCOP — typically 250–400%
- •Hot water system may also change if a new heat pump hot water cylinder is installed
- •SAP 10.2 applies a "seasonal performance factor" for heat pump systems that reflects real-world seasonal efficiency
Typical EPC improvement from a heat pump
| Property type / previous heating | Typical EPC before | Typical EPC after heat pump | Band change |
|---|---|---|---|
| 3-bed semi, gas boiler, average insulation | D (55–65) | C (69–78) | D → C |
| 3-bed semi, gas boiler, good insulation | C (70–75) | B (80–86) | C → B |
| 4-bed detached, oil boiler, poor insulation | E (35–45) | D (55–65) | E → D |
| 2-bed flat, gas boiler, average insulation | C (68–74) | B (80–87) | C → B |
| Victorian terrace, gas boiler, solid walls | E (40–50) | D (55–68) | E → D or D → C |
These are indicative ranges — the actual outcome depends on the specific property's SAP inputs. The key insight: the improvement from D to C (or E to D) is very common for gas-heated homes; the improvement from C to B is achievable but depends more on the property's insulation level than the heating system alone.
Why insulation matters for EPC improvement
A heat pump in a poorly insulated property will improve the EPC band (because the fuel switch and efficiency improvement are recorded in SAP), but the property will still have a relatively low absolute score because of its high heat loss. The EPC improvement from the heat pump is "portable" — it applies regardless of insulation level — but to move from band D to band B, most properties also need insulation improvements alongside the heat pump.
If your goal is specifically to reach EPC C for a future sale or mortgage purposes, getting a pre-installation EPC assessment by an accredited assessor will tell you exactly how many SAP points the heat pump will add, and whether any insulation improvements are also needed to reach the target band.
Getting your EPC updated after installation
Your existing EPC (if you have one) is valid for 10 years. After a heat pump installation, you need to commission a new EPC assessment to record the improvement — the old EPC will not automatically update. A new EPC assessment costs approximately £60–120 from an accredited domestic energy assessor (DEA). The MCS certificate from your installation provides the documentation the assessor needs to record the heat pump in the SAP calculation.
If you plan to sell your property, re-mortgage, or access any incentives tied to EPC band, getting an updated EPC promptly after installation is important. The EPC also affects the property's marketability — estate agents and portals increasingly display EPC band prominently, and the research on EPC C versus EPC D sale price premiums (4–6% in recent studies) creates a concrete financial incentive.
SAP 11: the upcoming update
SAP 11, the next major update to the EPC methodology, was under consultation as of 2025–2026. SAP 11 is expected to further reduce the carbon factor for electricity (reflecting grid decarbonisation) and may change how heat pump seasonal performance is modelled. When SAP 11 is adopted, properties with heat pumps may see their EPC scores improve automatically relative to gas-heated equivalents, even without further physical changes. The direction of travel favours early heat pump adopters.
Sources
- •DESNZ, SAP 10.2 — Standard Assessment Procedure for the energy rating of dwellings (GOV.UK)
- •Rightmove, EPC and property value research (2024)
- •Savills, Green premium research: EPC and house prices in England and Wales (2025)
- •DLUHC, EPC guidance for domestic properties (GOV.UK)
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Disclaimer: Prices and specifications correct as of April 2026. Always get a professional heat loss assessment before purchasing. We are not installers and do not provide heating advice.