Boiler Replacement Cost Calculator

Compare old vs new boiler efficiency. Calculate installation cost, annual savings and payback period.

Last updated: April 2026 · Source: GOV.UK — Boiler Upgrade Scheme

£

Install Cost

£2,800.00

Annual Saving

£246.81

Payback

11.3 years

10yr Net Saving

-£331.91

Old boiler: ~65% efficient. New A-rated: ~94%. Efficiency improvement: ~31%.

Disclaimer

This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.

How It Works

If your gas boiler is over 10-15 years old, replacing it with a modern condensing boiler or a heat pump can significantly reduce your energy bills. A new A-rated condensing gas boiler costs £2,000-£4,000 installed and operates at 90-94% efficiency compared to 60-80% for many older boilers.

The Boiler Upgrade Scheme (BUS) provides grants of £7,500 towards the cost of an air source or ground source heat pump, making them a viable alternative to a straight boiler replacement. To qualify, your home must have an EPC rating of D or better (or you must install insulation improvements first), and the scheme applies to England and Wales only.

This calculator compares the costs and savings of three options: replacing with a new gas boiler, installing an air source heat pump with the BUS grant, or installing a ground source heat pump with the grant. It factors in installation costs, annual running costs, maintenance and the projected payback period for each option.

Example: Replacing a 20-year-old boiler (65% efficiency)

  1. Current annual gas cost (65% boiler): £1,130
  2. New gas boiler (93% efficiency): £790/year — saving £340
  3. New boiler cost: £3,000, payback: 8.8 years
  4. ASHP (COP 3, with BUS grant): cost £4,500, running £980/year
  5. ASHP saving vs old boiler: £150/year at current tariffs
  6. ASHP payback: ~30 years (improves with solar/low tariff)

Source: GOV.UK — Boiler Upgrade Scheme

Frequently Asked Questions

What does the Boiler Replacement Cost Calculator do?
Compare old vs new boiler efficiency. Calculate installation cost, annual savings and payback period. All calculations are performed in your browser using official UK rates and thresholds.
Does this reflect the current energy price cap?
This calculator uses representative energy prices. The Ofgem energy price cap changes quarterly — check Ofgem's website for the latest cap level applicable to your region and payment method.
Can I save money by switching tariff?
Potentially yes. The energy market offers various fixed and variable tariffs. Use a comparison site authorised by Ofgem (such as Ofgem's own comparison tool) to check if switching could save you money.