Heat pump calculator
Heat pump vs gas boiler calculator for the UK
Compare an air-source heat pump with a gas boiler using UK unit rates, Boiler Upgrade Scheme grants, and your heat demand.
A heat pump wins when its COP is high enough to beat the old fuel after install cost and grants.
Before
Boiler running cost
After
Heat pump running cost
Your heat-pump payback
Change heat demand, gas price, electricity price, COP, installed cost, and BUS grant.
Decision signal
Not worth it yetThe default case does not recover the upfront cost. Use this as a negotiation or wait signal.
Annual saving
-£37
Simple payback
No payback
10-year net
-£5,370
This does not pay back with these assumptions. Try a lower upfront cost, higher usage, or better tariff spread.
Before vs after annual cost
lower is better| Decision number | Default | Why it matters |
|---|---|---|
| Upfront / net cost | £5,000 | The amount the savings must recover. |
| 5-year net | -£5,185 | Useful if you may move or replace equipment early. |
| 10-year net | -£5,370 | The long-run money signal after upfront cost. |
Old cost = useful heat / boiler efficiency x gas price. Heat-pump cost = useful heat / COP x electricity price.
Default values are source-backed planning benchmarks, not quotes. For the most accurate result, replace them with your own bill, tariff, vendor quote, grant, and usage numbers.
Before you buy
Use the calculator as a quote filter
1. Enter your real tariff
Use your bill or supplier app, not a sales estimate.
2. Add the actual quote
Net of grants, rebates, discounts, and installation extras.
3. Share the link
Keep everyone comparing the same assumptions.
Trust layer
- -No signup wall before the answer.
- -Sources are visible at the bottom of every calculator.
- -The result warns users when the math does not pay back.
Quick answers
Common questions
Is this heat pumps calculator exact?
It is a planning estimate, not a quote. Replace the defaults with your actual quote, tariff, usage, and incentive numbers before buying.
Why does payback change so much when I move the sliders?
Big energy purchases are sensitive to usage, local energy prices, upfront cost, and incentives. A small change in those assumptions can move payback by years.
Should I use this before talking to vendors?
Yes. The calculator gives you a neutral baseline so you can compare vendor claims against source-backed math.
Sources for this page
- Ofgem energy price cap, UK domestic electricity and gas unit-rate benchmarks.
- Boiler Upgrade Scheme, Heat-pump grant values for England and Wales.
- ENERGY STAR heat pump criteria, COP definition for heat-pump efficiency calculations.