Heat Pump vs Gas Boiler: Real UK Running Costs in 2026
Honest 2026 running-cost comparison of air source heat pumps versus modern gas combi boilers — with real UK tariffs, install costs and payback numbers.
I've installed both. Every homeowner I meet in 2026 wants to know the same thing: will a heat pump actually save me money, or is it a five-figure gamble? Here's the real maths using April 2026 UK tariffs.
The headline numbers
For a typical 3-bed semi using 12,000 kWh/year of heating and hot water:
| System | Annual energy cost | Install cost (after grant) |
|---|---|---|
| Modern A-rated gas combi | £948 (12,000 kWh × 7.9p) | £2,600 |
| Air source heat pump (COP 3.2) | £1,031 (3,750 kWh × 27.5p) | £6,500 (after £7,500 BUS grant) |
| ASHP on heat-pump tariff (18p) | £675 | £6,500 |
The heat pump only wins on running costs when you're on a specialist heat-pump tariff (Octopus Cosy, EDF Heat Pump, British Gas HomeEnergy Heat Pump). On a standard variable tariff, gas is still cheaper day-to-day.
Why the COP number matters more than the brochure
Coefficient of Performance (COP) is how many kWh of heat you get per kWh of electricity. Brochures quote COP 4+ tested at 7°C outside and 35°C flow. Real-world UK winter average is closer to 2.8–3.2 on retrofit installs. Ask your installer for their MCS commissioning SCOP figures on comparable homes — not the datasheet number.
Payback maths, honestly
Even on the best heat-pump tariff, the £6,500 net install cost pays back in roughly 24 years against a £2,600 gas boiler swap. That's longer than the heat pump will last. The financial case for switching today only stacks up if:
- Your existing boiler is dead and you'd be spending £2,600+ anyway;
- You have solar PV that can offset daytime electricity;
- You're planning to stay 15+ years and value the carbon reduction.
What most installers won't tell you
Retrofit heat pumps need larger radiators (often K2 or K3 upgrades), a bigger hot water cylinder (200L+), and decent loft insulation. Budget £800–£2,000 extra for those bits — the BUS grant doesn't cover them.
Does home emergency cover apply to heat pumps?
Most cover providers still exclude heat pumps or charge a premium. Our home emergency cover includes plumbing and electrical response even in heat-pump homes; ask about dedicated heat-pump service plans when you get a quote.
My verdict for 2026
If your combi is under 12 years old and working, keep it and re-evaluate in 2029. If it's dying now and you can afford the up-front premium, a heat pump on a specialist tariff is a fair choice — but it isn't the automatic money-saver Instagram makes it out to be. Read our combi vs system vs regular guide if you're leaning back toward gas.
FAQ
Do heat pumps work in cold UK weather?
Yes down to about -15°C, though efficiency drops. Every properly sized MCS install includes cold-weather backup logic.
Is the £7,500 BUS grant guaranteed until 2028?
The scheme is currently funded through March 2028. Don't leave it to the last week — installers get booked up.
Summary
- On standard tariffs, gas is still 25–35% cheaper to run in 2026.
- On a heat-pump tariff, running costs beat gas — but the install premium is 15–25 year payback.
- Retrofit properly (radiators, cylinder, insulation) or don't bother.