What this calculator models
Heat pumps are now the default low-carbon heating technology for UK homes that cannot stay on the gas grid through to 2050. The financial case depends on three numbers most calculators ignore: real SCOP at the design flow temperature for your radiators, real winter electricity tariff (not annual blended), and the capital cost of upgrading your emitters before the heat pump can run efficiently. This calculator surfaces all three. Payback periods of 8-15 years are realistic; sub-7-year claims usually hide one of those three numbers.
Inputs
- Floor area (m²)
- Property type and age band
- Current heating system (gas combi, gas system, oil, LPG, direct electric, storage heaters)
- Current annual heating spend
- Insulation level (loft, walls, floor)
- Glazing type and age
- Existing radiator type and design flow temperature
- Postcode (for regional gas-vs-electricity tariff differential and climate zone)
Outputs
- Modelled payback period (years)
- Annual saving (best case, base case, worst case)
- 10-year cumulative saving
- 25-year NPV
- Total capital cost net of any Boiler Upgrade Scheme contribution
- Tariff-sensitivity table (±20% on gas and electricity)
- SCOP sensitivity (3.0 / 3.5 / 4.0 scenarios)
- Carbon-saving estimate (tCO2e over 25 years)
Typical payback band: 8-15 years for a typical UK home, 12-18 years for older solid-wall stock without prior insulation work, sub-10 years for newer well-insulated detached stock with cheap-tariff arrangements
Best for: Owner-occupiers in homes off the gas grid, or on the gas grid but with at least loft and cavity insulation already in place, considering a boiler swap in the next 5 years.