Heat Pump vs Gas Boiler — 15-Year Cost Comparison (UK 2026)
Last reviewed: 13 May 2026
The actual 15-year total-cost-of-ownership comparison between a well-installed air source heat pump and a new gas boiler — capital cost, running cost, servicing — using verified UK figures and current tariffs.
In short
Across 15 years for a typical UK 3-bed semi, the all-in cost of a well-installed heat pump on a heat-pump-specific tariff lands at approximately £21,000–£25,000. The equivalent gas-boiler path — accounting for the typical boiler replacement at year 10–13 — lands at approximately £24,500–£25,500. A well-installed heat pump on a heat-pump tariff is roughly £3,500–£4,000 cheaper than gas over 15 years. But the comparison flips sharply with two specific failures: a heat pump left on the standard variable tariff runs ~£2,000–£3,500 above gas, and an underperforming heat pump (SCOP 2.5) on the standard tariff runs ~£8,500–£10,500 above gas. The technology category doesn’t determine the outcome — the install quality and tariff choice do.
On this page
- The 15-year framework
- Capital cost over 15 years
- Running cost over 15 years
- Servicing over 15 years
- The four-scenario total
- Why “well-installed” matters so much
- What happens after year 15
- Future Homes Standard — context for new-build buyers
- What the comparison rests on
- What this means for homes in Reading
The 15-year framework
A 15-year horizon is the standard comparison frame for residential heating because it covers roughly one full boiler replacement cycle (boilers typically last 10–15 years per the major UK manufacturers’ own guidance — Worcester Bosch, Baxi, Vaillant, Glow worm, Ideal) and the lower bound of a typical heat pump lifespan (15–20 years).
What’s in the comparison:
- Capital cost — the install at year 0, plus any replacement within the 15-year window
- Running cost — annual fuel cost across the period
- Servicing — annual service contracts
- Standing charges — daily charges (applied identically to both systems where both have electricity supply)
What’s not in the comparison: the opportunity cost of the upfront capital, property-value impact (covered in our property value guide), comfort or convenience differences, or carbon and environmental considerations beyond the financial.
Capital cost over 15 years
Heat pump path
| Item | Cost |
|---|---|
| Median UK ASHP install (2026, per Nesta/Ofgem BUS data) | £13,041 |
| BUS grant deduction | −£7,500 |
| Net install cost at year 0 | £5,541 |
| Heat pump replacement within 15 years | £0 (within design lifespan) |
| 15-year heat-pump capital total | £5,541 |
A heat pump installed in 2026 sits within its 15–20 year design lifespan for the full 15-year horizon. No replacement assumed during the period.
Gas boiler path
| Item | Cost |
|---|---|
| New gas boiler install (2026) | £3,000 |
| Boiler replacement at year 10–13 (manufacturer-stated 10–15 year lifespan) | £3,000–£4,000 |
| 15-year gas-boiler capital total | £6,000–£7,000 |
The gas-boiler path assumes one replacement within the 15-year horizon, which aligns with manufacturer guidance from the big 5 UK boiler manufacturers. Some boilers last 20+ years, but doing so usually involves rising repair costs in the later years.
Capital comparison
| 15-year capital | |
|---|---|
| Heat pump (net of BUS grant) | £5,541 |
| Gas boiler (incl. one mid-period replacement) | £6,000–£7,000 |
Counterintuitive result: heat pump capital is at or below gas-boiler capital across 15 years. The “heat pumps are expensive” framing usually rests on the year-0 sticker price (£13,041 before grant) without netting the £7,500 BUS grant and without acknowledging that gas boilers need replacing within the horizon.
Sensitivity: Without the BUS grant, heat pump capital sits at £13,041 vs gas £6,000–£7,000 — a ~£6,000 disadvantage. The grant is the lever that flips the capital arithmetic. The grant runs to 2030 per current regulations; installing in 2026–2030 captures the grant for the full 15-year window.
Running cost over 15 years
Using Q2 2026 Ofgem price cap figures (24.67p/kWh electricity standard variable; 5.74p/kWh gas) and a typical 3-bed semi annual heat demand of 17,700 kWh (per BEAMA):
Heat pump on heat-pump-specific tariff
- 5,060 kWh annual electricity (17,700 ÷ SCOP 3.5)
- Effective tariff rate ~17–20p/kWh (E.ON Next Pumped or British Gas Heat Pump with smart-controlled timing)
- Annual: £900–£1,000
- 15-year: £13,500–£15,000
Heat pump on standard variable tariff
- Same 5,060 kWh annual electricity
- 24.67p/kWh standard variable
- Annual: £1,250
- 15-year: £18,750
Gas boiler
- 19,667 kWh annual gas (17,700 ÷ 90% efficiency)
- 5.74p/kWh
- Annual: £1,130
- 15-year: £16,950
What the running-cost comparison shows
| Scenario | 15-year running cost |
|---|---|
| Heat pump, well-installed, heat-pump tariff | £13,500–£15,000 |
| Heat pump, well-installed, standard tariff | £18,750 |
| Heat pump, underperforming (SCOP 2.5), standard tariff | £26,000+ |
| Gas boiler (Ofgem standard variable) | £16,950 |
The well-installed heat pump on a heat-pump tariff runs ~£2,000–£3,500 below gas across 15 years. The standard-tariff heat pump runs ~£1,800 above gas. The underperforming-and-on-standard-tariff case runs ~£9,000 above gas.
The single largest lever in the heat pump vs gas comparison: tariff choice. The £4,000–£5,000 swing between standard tariff and heat-pump tariff over 15 years is bigger than the swing from most install-quality variables combined. A homeowner who installs a heat pump and stays on the standard variable tariff is losing the value the system is designed to deliver.
A note on price trajectory
The flat-rate assumption above is the conservative baseline. The directional signal: UK electricity supply is increasingly decoupling from gas as renewable share grows. By 2030, around 36% of UK generation is forecast to be under Contracts for Difference (fixed-price renewable contracts) — more than double the 2026 share. Gas prices, by contrast, remain exposed to wholesale market volatility and face structural pressure from declining North Sea supply.
If the realistic 15-year scenario includes a 1.5–3% real-terms rise in gas prices and 0–1% real-terms rise in electricity prices, the heat pump’s running-cost advantage widens by roughly £1,500–£3,000 over the period. We’ve kept the body arithmetic at flat-rate to avoid layering forecasts onto verified current figures.
Servicing over 15 years
- Heat pump annual service: £150–£300
- 15-year heat pump servicing: £2,250–£4,500
- Gas boiler annual service: ~£100
- 15-year gas boiler servicing: £1,500
Heat pump servicing runs higher per year — the gap (£50–£200/year, ~£750–£3,000 over 15 years) is real and offsets some of the running-cost saving.
The four-scenario total
Capital + running + servicing across 15 years:
| Scenario | Capital | Running | Servicing | 15-year total |
|---|---|---|---|---|
| Heat pump well-installed + heat-pump tariff | £5,541 | £13,500–£15,000 | £2,250–£4,500 | £21,300–£25,000 |
| Heat pump well-installed + standard tariff | £5,541 | £18,750 | £2,250–£4,500 | £26,500–£28,800 |
| Heat pump underperforming + standard tariff | £5,541 | £26,000+ | £2,250–£4,500 | £33,800–£36,000 |
| Gas boiler (standard variable, one mid-period replacement) | £6,000–£7,000 | £16,950 | £1,500 | £24,450–£25,450 |
The two scenarios most worth focusing on are the top one (heat pump done right) and the bottom one (gas continued):
- Heat pump well-installed + heat-pump tariff: ~£21,000–£25,000 over 15 years
- Gas boiler continued: ~£24,500–£25,500 over 15 years
A well-installed heat pump on the right tariff runs roughly £3,500–£4,000 cheaper than gas across the 15-year horizon.
The other two scenarios (heat pump well-installed on standard tariff, or underperforming heat pump on standard tariff) are warnings about what happens when the install is right but the tariff isn’t, or when the install itself is poorly done. Both are addressable problems — neither is inherent to the technology category.
Why “well-installed” matters so much
The four-scenario table makes the magnitude of “well-installed and well-tariffed” visible. The difference between the best heat pump scenario (£21,000) and the worst (£36,000) is £15,000 over 15 years — for the same property, with the same heat pump category, just different decisions about install quality and tariff.
The drivers of “well-installed”:
- A thorough heat-loss survey (per our installation process guide)
- Proper system sizing (not oversized “to be safe,” not undersized)
- Design at a low enough flow temperature to achieve SCOP 3.5+ — typically 45–50°C rather than 55°C
- Refrigerant choice that fits the property (R290 for higher flow temperatures, R32 for lower)
- Controls commissioning depth — weather compensation curve tuned to your specific property
- A 12-month review to refine controls based on real-world performance data
The drivers of “well-tariffed”:
- A smart meter capable of half-hourly readings (free from your supplier)
- A heat-pump-specific tariff (currently E.ON Next Pumped, British Gas Heat Pump, EDF Heat Pump Tracker — covered in our heat-pump tariffs guide)
- Smart controls that time the heat pump’s load into the tariff’s off-peak windows
None of these are technically difficult. They are addressable variables. The arithmetic above is the magnitude of the cost difference they make over 15 years.
What happens after year 15
The 15-year horizon is the standard comparison frame, but it actually understates the heat pump’s longer-term advantage:
- The gas boiler has typically been replaced once by year 15; a second replacement falls at year 20–25 at unknown future prices
- The heat pump is still within its design lifespan (15–20 years); the second decade runs at zero capital cost
- Heat-pump-specific tariffs will be materially better-developed by year 15 (2041)
- Gas price-trajectory sensitivity widens — by year 20, the running-cost gap could easily be £400–£600 a year in the heat pump’s favour
Energy Saving Trust and Ofgem 20-year projections suggest a well-installed heat pump saves approximately £3,900 vs gas across 20 years — directionally consistent with extending the 15-year arithmetic.
Future Homes Standard — context for new-build buyers
The Future Homes Standard (FHS) bans fossil-fuel heating in new-build homes from 2025, with legislation laid in December 2026 and a full transition completed by December 2027. New homes built from that date have heat pumps (or, in rare cases, district heating or alternative low-carbon systems) — no gas boilers.
There is no equivalent ban on existing homes. Earlier proposals for a 2035 phase-out of gas boiler sales were dropped, and there’s currently no confirmed legislative date for ending gas boiler sales to existing properties. The government’s position has been explicit: “will not force anyone to rip out a working boiler.”
The practical implication for Reading homeowners with existing properties: the gas boiler vs heat pump decision remains a choice, not a deadline. The 15-year arithmetic above is the financial input to that choice; the personal preferences (carbon, comfort, technology preference, install disruption) are the others.
What the comparison rests on
The 15-year arithmetic depends on four major assumptions. Each is transparent and each is verifiable:
- BUS grant available at year 0. The £7,500 BUS grant runs until 2030 per current regulations. Homeowners installing 2026–2030 capture the grant for the full 15-year window. Post-2030, the capital picture depends on what (if anything) replaces the BUS scheme.
- Achieved SCOP 3.5 for well-installed heat pump. Conservative real-world target (HeatpumpMonitor.org installs average 3.87 across 252 monitored systems). Underperforming installs at SCOP 2.5 are the failure case, identifiable at 12-month review.
- Tariff choice — heat-pump-specific vs standard variable. The £4,000–£5,000 swing across 15 years between the two is the single largest lever in the comparison. Active choice, not a default.
- Boiler replacement at year 10–13. Aligns with manufacturer-stated typical lifespans from Worcester Bosch, Baxi, Vaillant, Glow worm, Ideal. Some boilers last 20+ years but with rising repair costs in the later years.
Plus the implicit flat-rate price assumption, with the sensitivity discussion above showing how it cuts.
The arithmetic is not a forecast. It’s a structured comparison of two paths under stated baseline assumptions, with the sensitivities made transparent.
What this means for homes in Reading
Reading housing-stock distribution maps onto the 15-year comparison in roughly the following way:
Modern estates in Lower Earley, Woodley, and the western expansion areas typically deliver the best heat pump outcomes — installs tend toward the lower end of the cost range; SCOP after commissioning tends to land at 3.7–4.0; running costs sit at the cheap end of the heat-pump-tariff range. The 15-year heat-pump-vs-gas advantage in these properties is typically £4,000–£5,500.
Inter-war semis in Tilehurst, Earley, Whitley, and parts of Caversham are the typical case. Installs are middle-of-range; SCOP after radiator upgrades and proper commissioning lands at 3.5–3.8; 15-year advantage typically £3,000–£4,500.
Victorian and Edwardian terraces in central Reading and lower Caversham have higher heat demand and may need R290 systems to deliver useful efficiency at higher flow temperatures. Install costs sit at the upper end (more radiator work); SCOP after careful design lands at 3.2–3.6; running costs scale up proportionally with heat demand. 15-year arithmetic typically still favours the heat pump but by a smaller margin — £1,500–£3,000 — and the calculus is more sensitive to install quality.
For all property types in Reading, the tariff-switching lever is identical — £200–£350 a year, ~£4,000–£5,000 over 15 years. This is the single most reliable cost-reduction step a Reading homeowner can take post-install.
The 15-year horizon also captures the long-term policy direction: while there’s no ban on existing-home gas boilers, the government policy direction (Net Zero target, Warm Homes Plan, ongoing BUS scheme + Future Homes Standard) all point toward electrified heating becoming the default. A heat pump installed in 2026 is on the right side of that trajectory for the next 15+ years.
Related guides
- How much does a heat pump cost in 2026? — the capital-cost picture that feeds this comparison.
- How much does a heat pump cost to run? — the running-cost picture that feeds this comparison.
- Heat pump payback period — the honest answer — the simpler single-question version of this 15-year analysis.
- Heat-pump electricity tariffs compared — the deep look at the single biggest lever in the comparison.
Get a quote and a 15-year projection for your specific Reading home
Headline figures set expectations; only a property-specific design lands an accurate 15-year picture. Our free in-home survey includes a full heat-loss calculation, design SCOP for your specific system, a written quote with the £7,500 BUS grant deducted, and a 15-year cost projection comparing your specific property’s heat pump scenario against continuing with gas.
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