Heat Pump vs Gas Boiler 2025: Costs, EPC Impact & Which to Choose
The heating system is one of the biggest factors in your EPC score. Switching from a gas boiler to an air source heat pump can add 10–30 EPC points — but it is not the right choice for every home. Here is how to decide.
At a Glance: Side-by-Side Comparison
| Factor | Air Source Heat Pump | New A-Rated Gas Boiler |
|---|---|---|
| Installation cost | £8,000–£16,000 (less £7,500 BUS grant) | £1,500–£3,500 |
| Annual running cost* | £800–£1,500 | £900–£1,800 |
| EPC score impact | +10 to +30 points | +5 to +15 points (if replacing old boiler) |
| Lifespan | 20–25 years | 10–15 years |
| Carbon emissions | Very low (runs on electricity) | Moderate (gas combustion) |
| Works with existing radiators? | Needs larger radiators in some rooms | Yes, drop-in replacement |
| Works in poorly insulated homes? | Reduced efficiency — insulate first | Yes |
| Government grant available? | Yes — £7,500 BUS grant | No (unless ECO4 eligible) |
| Ofgem approval required? | MCS-certified installer required | Gas Safe registered engineer |
* Running costs assume a 3-bed semi, 2025 energy prices. Ofgem price cap from January 2025: electricity 24.5p/kWh, gas 6.24p/kWh (typical unit rates, may vary by tariff).
EPC Score: How Each System is Rated
The EPC calculation (SAP 10.2) uses a carbon emissions factor for each fuel type. Because electricity has a much lower carbon factor than gas under the current grid mix, heat pumps score very well on the environmental impact section of the EPC — and this flows into the energy efficiency score too.
Old gas boiler (G or F rated)
An inefficient older boiler — say a non-condensing model from the 1990s — can be the single biggest drag on your EPC. Replacing it is always worth doing.
Replacing with a new A-rated condensing boiler: typically +5 to +15 points.
New A-rated condensing boiler
A modern condensing gas boiler achieves around 90–95% efficiency. For many D-rated properties, this alone can push into the top of band D or into C.
Score improvement vs old boiler: +8 to +15 points. Best for: well-insulated homes where heat pump isn't viable.
Air source heat pump (ASHP)
ASHPs move heat from outside air into the home using electricity. Because electricity's carbon factor has fallen as renewables grow, SAP now favours electric heating heavily.
Score improvement vs old gas boiler: +15 to +30 points. Best for: well-insulated homes, properties looking to reach Band B or above.
Get a Fixed-Price Boiler Quote
A new A-rated condensing boiler can cut your heating bills by up to 30%. BOXT offers fixed-price quotes online with next-day installation available.
New boiler: typical savings £200–£400/year vs old inefficient model
Get a Fixed QuoteCompare Heat Pump Quotes
An air source heat pump can add 15–30 EPC points and qualifies for the £7,500 Boiler Upgrade Scheme grant. Compare quotes from MCS-certified installers.
£7,500 Boiler Upgrade Scheme grant available — reduces install cost to £2,000–£8,000
Compare Heat Pump QuotesThe £7,500 Boiler Upgrade Scheme (BUS)
The Boiler Upgrade Scheme (BUS) provides a £7,500 upfront grant towards the cost of an air source heat pump, taken directly off the installation invoice. The grant is applied by the installer — you never see the money, it just reduces your bill.
BUS eligibility checklist
Property is in England or Wales (separate scheme for Scotland)
Property has a current, valid EPC (not rated F or G for cavity wall / loft insulation deficiencies that could be cheaply fixed)
Installer is MCS-certified
Property does not have an existing heat pump installed
Application must be made by the installer, not the homeowner
After the £7,500 grant, a typical ASHP installation costs £2,000–£8,000 net depending on property size. The scheme is due to run until March 2028, though the budget is reviewed annually.
When a Gas Boiler Still Makes More Sense
Heat pumps are not the right answer for every home. Stick with a new gas boiler if:
Your home is poorly insulated
Heat pumps work at lower flow temperatures (around 45°C vs 70°C for a boiler). In a leaky, poorly insulated home, this means you run it for longer hours to maintain comfort — wiping out the efficiency gains. Sort your insulation first.
You have a short tenure
If you are selling within 2–3 years, the upfront cost of a heat pump (even after the grant) is hard to recoup versus a new boiler. New boilers have a clear, demonstrable impact on the EPC and can be factored into the asking price.
You have a high-pressure system you rely on
Heat pump systems typically need a separate hot water cylinder. If you have a combi-boiler setup in a small property, the pipework changes can be disruptive and costly.
Your electricity supply is restricted
ASHPs draw 2–5kW continuously in cold weather. Older properties with single-phase 60A supplies may need an electrical upgrade. Your installer should check this before quoting.
Finance Your Home Improvements
Energy improvements like solar, insulation, and boiler replacement can cost £2,000–£15,000. Compare personal loans from top UK lenders — get a quote in minutes with no impact on your credit score.
Estimated improvement cost: £2,000–£8,000 for heat pump after BUS grant
Compare Loan RatesFrequently Asked Questions
Does a heat pump always improve your EPC rating more than a boiler?
In most cases, yes — because the SAP calculation currently favours electricity over gas due to lower carbon intensity. An ASHP typically adds 15–30 EPC points vs 5–15 for a new A-rated gas boiler. However, the exact gain depends on your current system and property characteristics.
How much does an air source heat pump cost after the BUS grant?
After the £7,500 Boiler Upgrade Scheme grant, a typical ASHP installation costs £2,000–£8,000 depending on property size and required work (radiator upgrades, hot water cylinder, etc.). A new gas boiler costs £1,500–£3,500 all-in.
Are heat pump running costs cheaper than gas?
It depends on the electricity-to-gas price ratio. At current Ofgem price cap rates (electricity ~24.5p/kWh, gas ~6.24p/kWh), a heat pump with a COP of 3 (producing 3 units of heat per unit of electricity) costs roughly 8p/kWh of heat — slightly more than gas at around 7p/kWh. The gap narrows as the electricity price cap falls and the grid decarbonises.
What EPC rating do I need to qualify for the Boiler Upgrade Scheme?
Your property must have a valid EPC. If the EPC recommends loft or cavity wall insulation as a low-cost measure, you must install that first (or have a valid exemption) before applying for BUS. There is no minimum EPC band requirement.
How long does a heat pump last?
A well-maintained air source heat pump lasts 20–25 years, roughly twice the lifespan of a gas boiler (10–15 years). Over a 20-year period, you would typically replace a boiler once, while the heat pump runs for the full term — an important factor when calculating total cost of ownership.
Can a heat pump work with my existing radiators?
Sometimes. Heat pumps work at lower flow temperatures, so existing radiators may need to be 20–50% larger to deliver the same heat output. A heat pump installer will do a room-by-room heat loss calculation and identify which, if any, radiators need upgrading. Underfloor heating is ideal for heat pumps.
See What Your EPC Says About Your Heating System
Your EPC lists your current heating system rating and the estimated score gain from upgrading. Look up your property's certificate for free.
Look up your EPC rating for free