What is a heat pump COP?

COP = Coefficient of Performance = heat output ÷ electricity input. A modern air-source heat pump (ASHP) runs at 2.8–3.5 COP averaged over a UK heating season (the seasonal version is called SCOP). For every 1 kWh of electricity it pulls in roughly 3 kWh of heat. Ground-source heat pumps (GSHP) hit 3.5–4.5 SCOP but cost double to install.

What is the BUS grant?

The Boiler Upgrade Scheme (England & Wales) gives £7,500 toward an air-source or ground-source heat pump installation, replacing a fossil-fuel boiler. Scotland has the Home Energy Scotland Grant (up to £7,500 + £7,500 interest-free loan). Both schemes require MCS-certified installs and EPC C+ ratings. Confirmed running through 2028.

Are heat pumps cheaper to run than gas boilers?

Depends on the price ratio. A heat pump with SCOP 3.0 needs electricity to be no more than 3× the gas price per kWh to break even. UK gas is ~6p/kWh and electricity ~28p/kWh — a 4.7× ratio, so a heat pump is currently more expensive on standard tariffs. With a heat pump tariff (Octopus Cosy ~13p/kWh off-peak) it's roughly equal to gas. EU and US rates vary widely.

Will my house need new radiators?

Often yes. Heat pumps run at lower flow temperatures (35–55°C vs 60–80°C for gas), so you need larger surface area to deliver the same heat. About 30–50% of older UK homes need at least some radiator upgrades. Underfloor heating is ideal. A good MCS install includes a heat-loss calculation per room and recommends upgrades.

Is a heat pump worth it in 2026?

After the BUS grant a heat pump install is typically £6K–£10K out of pocket vs £2.5K–£4K for a new gas boiler. Running cost parity is achievable on a heat pump tariff. Carbon savings are immediate and large (~3 tonnes CO₂/year vs gas). With UK gas prices rising and electricity decarbonising, the long-term economics favour heat pumps. For early adopters it's a 10–15 yr financial decision and a good environmental decision.

♨️ Heat Pump vs Gas Boiler Calculator

15-year total cost comparison of an air-source heat pump versus a gas boiler. Includes UK BUS grant, fuel prices, maintenance and CO₂ savings.

Annual Heat Demand (kWh)UK avg ~12,000 kWh. Small flat ~6K, large house 18K+.

Currency

♨️ Heat Pump (ASHP)

Install Cost

Government Grant

SCOP (efficiency)

Electricity price (per kWh)

Annual servicing

🔥 Gas Boiler

Install Cost

Boiler Efficiency (%)

Annual servicing

Gas price (per kWh)

Annual fuel inflation (%)

⚠️ Estimate only. Real SCOP depends on radiator size, insulation, weather and installer skill. Get an MCS heat-loss survey before committing. Heat-pump-specific tariffs (Octopus Cosy, OVO Heat Pump Plus) can dramatically improve running costs not modelled here. Not financial advice.

Heat Pump vs Gas Boiler — The Decision in 2026

The economics of replacing a UK gas boiler with an air-source heat pump (ASHP) depend on three numbers: the install cost gap (after grants), the electricity-to-gas price ratio, and the SCOP (seasonal efficiency) you'll actually get. Get all three right and a heat pump matches or beats gas on lifetime cost. Get them wrong and you'll pay more.

Install Costs (UK May 2026, fully fitted)

New combi gas boiler: £2,500–£4,000
System gas boiler with cylinder: £3,500–£5,500
Air-source heat pump (8–12 kW): £10,000–£16,000 (before grant)
Ground-source heat pump: £18,000–£35,000 (before grant)
Boiler Upgrade Scheme (BUS) grant: £7,500 toward ASHP/GSHP

So a typical UK install gap is £6K–£8K extra for a heat pump after the grant.

Running Cost Maths

To produce 12,000 kWh of heat in a UK home with average kit:

92% efficient gas boiler: 12,000 ÷ 0.92 = 13,043 kWh of gas × 6p = £783/year
SCOP 3.0 heat pump: 12,000 ÷ 3.0 = 4,000 kWh of electricity × 28p = £1,120/year on standard tariff
Same heat pump on Octopus Cosy off-peak (~13p/kWh): ~£520/year — beats gas decisively

The Tariff Lever

Heat-pump tariffs are the killer feature. Octopus Cosy charges ~13p/kWh during three off-peak windows when the heat pump can do most of its work charging a buffer tank or running flow temps higher. OVO Heat Pump Plus caps electricity at gas-equivalent prices for verified heat-pump users. With these tariffs, heat pump running costs match or undercut gas.

Will a Heat Pump Work in My House?

Insulation: EPC C or better is best; D is workable; E or worse — fix insulation first
Radiators: 30–50% of homes need at least some larger rads (heat pumps run cooler flow temperatures)
Outdoor space: ~1 m × 1 m ground space + 1 m clearance for ASHP outdoor unit
Hot water: a hot-water cylinder is required (combi boilers without one need replacement plumbing)
Power supply: single-phase usually fine; check with installer

Carbon Savings

A typical heat pump cuts heating-related CO₂ by ~70%. UK gas emits 0.182 kg CO₂/kWh; UK grid electricity is now ~0.21 kg CO₂/kWh and falling. So 12,000 kWh of heat from gas → 2.4 tonnes CO₂; from a SCOP 3.0 ASHP → 0.84 tonnes — a ~1.6 tonne annual saving. Over 15 years that's ~24 tonnes — equivalent to taking a car off the road for 6 years.

What This Calculator Doesn't Include

Radiator/cylinder upgrade costs (often £500–£3,000 for older homes)
Heat-pump-specific electricity tariffs (Octopus Cosy, OVO Heat Pump Plus)
Solar PV synergy (free daytime electricity boosts heat pump economics massively)
Future gas price rises (Ofgem cap rose ~50% over 2021–2024)
Property value uplift / EPC rating improvement

⚠️

Important Note: Always commission an MCS heat-loss survey before ordering a heat pump — undersized units cycle and underperform; oversized units waste money. Get three MCS-certified quotes. The BUS grant requires the installer to apply on your behalf. Pair with our Solar Panel Calculator if you're considering both — together they transform running costs.

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