Heat Pump vs Gas Boiler
Comparing air source heat pumps and gas combi boilers for UK homes in 2026.
Quick Comparison Table
| Feature | Air Source Heat Pump | Gas Combi Boiler |
|---|---|---|
| Installation cost | £7,000–£14,000 Minus £7,500 BUS grant = £0–£6,500 net | £2,500–£4,000 No grant available |
| Annual running cost | £800–£1,200 3-bed semi, 12,000 kWh/yr heat demand | £600–£800 Same property |
| Efficiency (SCOP / ErP) | 300% (SCOP 3.0 typical) Delivers 3 kWh heat per 1 kWh electricity | 90–94% (A-rated) Loses 6–10% to flue |
| Carbon emissions | 0.6–0.8 kg CO₂e per kWh heat Grid electricity (2026 mix) | 2.0 kg CO₂e per kWh heat Direct fossil fuel combustion |
| Lifespan | 15–20 years (20+ with maintenance) | 10–15 years |
| Best for | Well-insulated homes, underfloor heating, low-carbon goals | Existing radiator systems, budget-constrained, on-demand hot water |
Installation Costs
As of 2026, a typical air source heat pump installation for a 3-bedroom UK home costs £7,000–£14,000 including the outdoor unit, indoor buffer tank, pipework, and radiator upgrades if needed. The UK government's Boiler Upgrade Scheme (BUS) provides a £7,500 grant (no means-testing), bringing the net cost down to £0–£6,500.
A gas combi boiler replacement costs £2,500–£4,000 installed. No government grant is available for gas boilers. With the BUS grant, a heat pump's upfront cost is competitive with or lower than a gas boiler in many cases.
Running Costs
Running costs depend on energy prices, which fluctuate. Using 2026 UK average rates (24p/kWh electricity, 6p/kWh gas):
- Heat pump (3-bed semi, 12,000 kWh/yr heat)
- £960/year electricity (assuming SCOP 3.0)
- Gas boiler (same property)
- £720/year gas (assuming 90% efficiency)
Heat pumps currently cost £200–£400 more per year to run than gas boilers at standard tariffs. However, heat-pump-specific electricity tariffs (e.g. Octopus Cosy) offer lower rates (15–18p/kWh off-peak), which can reduce the running cost gap to near zero.
Efficiency & Performance
Heat pumps are 300% efficient (SCOP 3.0 typical for UK climate), meaning they deliver 3 kWh of heat for every 1 kWh of electricity consumed. Gas boilers are 90–94% efficient (A-rated condensing models), meaning 6–10% of the gas energy is lost to the flue.
In energy terms, heat pumps are more efficient. However, because electricity is more expensive per kWh than gas in the UK, the cost efficiency depends on tariffs.
Carbon Emissions
Heat pumps powered by the 2026 UK grid (which is ~60% renewable/nuclear) emit 0.6–0.8 kg CO₂e per kWh of heat delivered. Gas boilers emit 2.0 kg CO₂e per kWh of heat, as they burn fossil fuel directly.
A heat pump reduces a typical 3-bedroom home's heating emissions by 60–70% compared to a gas boiler. As the UK grid decarbonises further, heat pump emissions will approach zero.
Which Should You Choose?
Choose a heat pump if:
- Your home has good insulation (EPC rating C or better)
- You want to reduce carbon emissions
- You're willing to switch to a lower-rate electricity tariff
- You qualify for the £7,500 BUS grant
- You're installing underfloor heating or oversized radiators
Choose a gas boiler if:
- Your home is poorly insulated and you can't afford retrofit
- You need on-demand instant hot water
- You're on a tight budget (even with the grant, some heat pump installs exceed £6,500 net)
- You have existing radiators that would be expensive to upgrade
Related Guides
Sources
- UK Government Boiler Upgrade Scheme (BUS) guidance, 2026. gov.uk
- Energy Saving Trust, "Heat Pumps: A Guide for Homeowners", 2026. Accessed June 2026.
- Ofgem, "Default Tariff Cap" (Q2 2026 rates: 24.5p/kWh electricity, 6.04p/kWh gas).
- MCS, "Heat Pump Performance Data" (SCOP 2.8–3.2 typical for UK climate, 2023–2026).
- UK BEIS, "Greenhouse Gas Reporting: Conversion Factors 2026" (grid electricity 0.19 kg CO₂e/kWh, gas 0.18 kg CO₂e/kWh fuel).
- Which?, "Heat Pump Installation Costs" (£7,000–£14,000 range, 2025–2026 survey).
- Octopus Energy, "Cosy Octopus" tariff structure (15p/kWh off-peak for heat pump customers, 2026).
Last reviewed: 2026-06-27