When heat pump wins clearly
Off-gas-grid (oil, LPG, electric storage): payback 5–7 years, savings £1,000–£1,700/year.
Long-term ownership (10+ years): heat pump lifespan 20+ vs boiler 10–15 means avoiding 1–2 boiler replacements.
Eligible for BUS grant (England/Wales) or HES Cashback (Scotland): grant covers the install-cost gap.
Decent insulation already in place: SCOP 3.0+ delivers strong running-cost performance.
Carbon-conscious: heat pump 4.7× lower carbon intensity per kWh of heat at 2026 UK grid factors.
When gas boiler can still win
On mains gas, well-insulated home, staying 3–5 years: short-horizon financial maths can favour boiler.
Hard-to-retrofit listed building: planning friction + heritage-spec costs can push heat pump to £15,000+.
Ineligible for BUS grant (existing heat pump, social-rented tenant, etc.): full £8,000–£14,000 cost.
Very small flat with no outdoor unit space: flat space constraints sometimes make installation impractical.
Grant uncertainty: BUS scheme runs to 2028 and is subject to change — boilers don't have grant-cliff risk.
Side-by-side at typical UK 3-bed semi
Install cost: heat pump £10,800 before grant / £3,300 after = £3,300 net. Gas boiler £2,500–£4,500.
Annual heating + hot water (12,800 kWh/year): heat pump £930 (Cosy tariff) vs boiler £1,180 = £250 saving.
Lifespan: 20 years vs 12 years. Over 25 years, expect 1–2 boiler replacements (£3K–£9K).
Maintenance: heat pump ~£100/year service. Gas boiler ~£100/year service. Equivalent.
Comfort: heat pumps run gentler heat (45–55 °C flow) — reported equally comfortable in EST 2024 trial (n=750).
FAQ
Will my gas bill go up if I keep the boiler?
Likely yes. The Climate Change Committee projects rising gas costs through 2030 as the UK transitions away from gas heating. Switching to a heat pump locks in electricity-based running costs which are projected to fall as the grid decarbonises.
Can I keep my boiler as backup?
Some installers offer hybrid setups, but hybrid systems do NOT qualify for the £7,500 BUS grant. If you want a backup, an electric immersion heater built into the heat pump cylinder is a more grant-friendly approach.
Which has more reliable parts availability?
Gas boilers — well-established UK service network. Heat pumps are catching up rapidly; major brands (Daikin, Mitsubishi, Vaillant, Samsung) have UK parts depots, but rare-fault repair times can run 2–4 weeks vs same-week for a boiler.
What about hot water performance?
Heat pumps deliver hot water at 50–60 °C (same as combi boilers), with anti-Legionella cycles weekly raising temperature briefly to 60+ °C. Hot water storage capacity is 180–300 litres typical (vs combi boilers' on-demand hot water).
Sources
- Energy Saving Trust 2024 UK Heat Pump Trial
- Climate Change Committee — UK net-zero pathway
- Ofgem energy price cap data
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Continue your research with these locally-sourced UK heat pump articles.
Oil Boiler or Heat Pump? UK 2026 honest comparison.
1.5M UK homes still heat with oil. Switching to a heat pump saves £1,500–£2,500/year and pays back in 4–6 years. Detailed cost comparison, BUS grant priority, and regional patterns.
LPG Boiler or Heat Pump? UK 2026 honest comparison.
~400,000 UK homes heat with LPG. Switching to a heat pump saves £1,300–£2,000/year and pays back in 4–6 years. Detailed cost comparison, BUS grant priority, regional patterns.
Storage Heaters or Heat Pump? UK 2026 strongest payback.
1.2M UK homes use electric storage heaters. Switching to a heat pump saves £900–£1,800/year and pays back in 3–5 years — the strongest UK conversion case. £7,500 BUS grant applies.