Heat Pump Cost Calculator
How it works
The estimator combines property size, current heating fuel and insulation level to size a heat pump (kW), estimate install cost, and project annual running cost using a realistic SCOP of 3.0–3.6. The £7,500 BUS grant is applied automatically. Off-gas homes (oil, LPG, electric) almost always save money; on-gas savings depend on tariff.
Worked example
3-bed semi, currently gas, EPC C: 7kW heat pump, £11,500 install − £7,500 grant = £4,000 net. Running on Cosy tariff: ~£950/yr vs £1,100 gas. Saves ~£150/yr; payback on net cost ~25 years (longer than the lifetime). Real wins are in off-gas oil/LPG homes saving £600–£1,200/year.
Who should use this
- •Off-gas homes on oil, LPG or electric heating
- •Owners doing a deep retrofit with new radiators
- •Anyone replacing a boiler in a well-insulated home
Common mistakes
- ×Installing without a proper room-by-room heat loss survey
- ×Keeping undersized radiators — heat pumps run cooler so radiators must be larger
- ×Not switching to a heat-pump tariff after install
- ×Choosing a system based on price alone rather than MCS installer reputation
Frequently asked questions
Do I need underfloor heating?▾
No — properly sized radiators work fine. UFH is a bonus, not a requirement.
Will it heat the house in -5°C?▾
Yes. UK heat pumps are rated to -7°C minimum and most operate down to -15°C, just less efficiently.
Is the £7,500 grant guaranteed?▾
BUS is funded to 2028 with £1.5bn allocated. First-come-first-served via MCS installers.