Heat Pump Cost Calculator

The total installed cost of an air source heat pump (ASHP) in the UK in 2025/26 ranges from approximately £8,000 for a small property to £18,000 for a large detached house. This includes the heat pump unit, labour, a hot water cylinder (if needed), and any required upgrades to pipework or radiators. After the £7,500 BUS grant, the net cost to a homeowner is typically between £500 and £10,500 depending on property size.

Ground source heat pumps cost more — typically £15,000–£35,000 — due to the ground loop installation (borehole or trench). They are more efficient but require suitable land or planning consent for a vertical borehole.

• Property size: Bigger homes need larger heat pump units (measured in kW output). A 3-bed semi might need a 7–9kW unit; a large detached may need 12–16kW.
• Existing radiators: Heat pumps work best at lower flow temperatures, which may require larger or additional radiators. Replacing undersized radiators adds £500–£3,000 to the project.
• Hot water cylinder: Most gas boiler homes need a new hot water cylinder, adding £500–£1,500.
• Insulation: Poor insulation increases heat pump running costs because the system has to work harder. Improving insulation first (loft, cavity wall) typically costs £500–£2,500 and significantly improves running costs and comfort.
• Location: Prices tend to be higher in London and the South East.

Heat pump running costs depend on the electricity tariff and the system's Coefficient of Performance (COP) — a measure of efficiency. A well-installed modern ASHP typically runs at a COP of 2.5–4.0, meaning it produces 2.5–4 kWh of heat for every 1 kWh of electricity used.

At current energy prices (April 2026 price cap), running costs for a heat pump are broadly comparable to gas for well-insulated homes. Households replacing oil or LPG — where fuel prices are higher and less stable — typically see the best savings, often £500–£1,200 per year.

Specialist heat pump electricity tariffs (such as Octopus Cosy or similar time-of-use tariffs) can reduce running costs by 15–25% by running the system during cheaper overnight periods.

After the £7,500 BUS grant, payback periods in the UK are typically:

• Replacing oil or LPG in a medium, well-insulated home: 5–10 years
• Replacing gas in a medium, well-insulated home: 10–18 years
• Replacing gas in a poorly insulated home: 18–25+ years (insulation upgrades strongly recommended first)

Heat pumps typically last 15–25 years with minimal maintenance — significantly longer than gas boilers (typically 10–15 years). The long-term economics often favour heat pumps over a 20-year horizon, even in marginal cases.