Gas boiler replacement:
do it now, or wait for the heat pump?
UK households face a once-in-a-generation choice. Gas boilers cost £2,500-£3,500 installed. Heat pumps cost £10,000-£14,000, but the £7,500 Boiler Upgrade Scheme (BUS) grant covers most of the gap. Plus heat pumps use 3.2× less primary energy per kWh of heat. The calculator stacks the maths over 10 years.
Current boiler age (years)
New gas boiler installed cost (£)
Annual gas bill (£)
Annual heating demand (kWh)
Heat pump installed cost (£)
Electric rate (£/kWh)
Replace with a heat pump now.
Strong 10-year savings + your current boiler is at end-of-life. Apply for the £7,500 BUS grant before installing.
HP payback (years)
2.6
on upfront delta
10-yr saving (HP)
£3,347
vs new gas
10-year total
COP 3.2 (typical UK air-source heat pump, EN 14511 SCOP). BUS grant £7,500 from Ofgem (England & Wales, March 2026). Excludes insulation upgrade costs (often required for heat pump to perform, check your EPC).