If you've been trying to work out whether to replace your boiler with another one or switch to a heat pump, you are not alone — and the noise around this decision is deafening. Most of it comes from people with something to sell. What follows is what the installed data actually says, pulled from OMEGA's own fleet of air-source heat pumps across Essex, Suffolk, Kent and Cambridgeshire, alongside the gas boilers we still install every week.
Heat pump vs gas boiler — what the upfront cost looks like
| System | Upfront | Lifespan |
|---|---|---|
| Condensing gas boiler (combi, 30kW) | £2,800–£3,500 | 10–15 years |
| System boiler + unvented cylinder | £3,800–£4,800 | 10–15 years |
| Air-source heat pump (5-7kW) + cylinder | £11,000–£14,000 | 15–20 years |
| Heat pump after £7,500 BUS grant | £3,500–£6,500 | 15–20 years |
Once you apply the £7,500 Boiler Upgrade Scheme (BUS) voucher, the upfront gap between a heat pump and a system boiler shrinks to around £2,000 on an average 3-bed semi. On some of the installs we quote, the heat pump is genuinely cheaper to buy than a new gas system — something that would have sounded far-fetched two years ago.
Running costs — what each one actually costs to heat your home
This is the bit that trips most people up in the pub. Heat pumps run on electricity, which costs more per unit than gas. But they move around 3 kWh of heat for every 1 kWh of electricity they use (a COP of 3.0–3.5 in a well-sized UK install), so the comparison that matters is pence per useful kWh of heat delivered into your radiators.
| System | Effective p/kWh of heat |
|---|---|
| Condensing boiler (92% efficient) | ~7.6p |
| Air-source heat pump, standard tariff (COP 3.2) | ~8.8p |
| Air-source heat pump, Octopus Cosy (COP 3.2) | ~4.4p |
On a standard electricity tariff, a heat pump runs roughly 15% more per useful kWh than gas. Switch to a dedicated heat-pump tariff — Octopus Cosy, British Gas Heat Pump, E.ON Heat — and it's around 40% cheaper. In other words, the tariff you pick after install matters more than the technology itself. That is a huge thing to miss, and most installers never mention it.
When a heat pump is the smarter choice
- EPC-rated D or above homes with decent insulation already in place. A properly insulated 3-bed semi on a heat-pump tariff runs at roughly £950 a year for heating and hot water combined.
- Any home off the gas grid. Oil and LPG are both more expensive than running a heat pump even on standard electricity — so the switch pays back faster.
- New builds and extensions. The marginal cost against a gas system is smaller, and you usually end up with underfloor heating in the same project, which is where a heat pump genuinely thrives.
- Households that already have solar PV. Heat pumps pair with rooftop generation far better than gas ever could — a typical 4 kWp array offsets roughly 35% of annual heat demand.
When a gas boiler is still the right call
- EPC F and G homes with draughty fabric. A heat pump in a leaky Victorian house will struggle on the coldest days and the running-cost savings evaporate — fix the fabric first, then talk pumps.
- Tight budgets without BUS eligibility. If the grant doesn't apply to your property, the payback stretches to 12–15 years, which may be longer than you want to commit.
- Tenants and short-term occupants. Heat-pump paybacks play out over many years — if you're moving in three, a good A-rated combi is the rational call.
- Homes with no outdoor setback for the external unit. Mid-terrace houses with only a narrow back garden often lack the clear airflow the unit needs to run efficiently.
The £7,500 Boiler Upgrade Scheme, plain-English
The Boiler Upgrade Scheme pays £7,500 towards an air-source or ground-source heat pump install. It's funded through Ofgem and available to homeowners in England and Wales. Your installer handles the voucher — you never fill in a form yourself. Eligibility takes about thirty seconds to check.
- You own the property (or you're the landlord).
- You have a valid EPC less than 10 years old.
- No outstanding loft or cavity wall recommendations on the EPC — if there are, they need doing first, and they usually qualify for ECO4 or GBIS anyway, so it's a sequencing thing not a blocker.
- The installer is MCS-certified. OMEGA is MCS-registered, TrustMark-registered, and works to PAS2030.
Your next step — a free 45-minute survey
If you'd like real numbers for your house — heat-loss calculation, BUS eligibility, and honest side-by-side running costs for both options — a home energy survey is the quickest way to get them. Book online or call free on 0800 229 4094, Monday to Saturday. No cost. No obligation. No pressure.
Want to find out how much you could save?
Book a free 45-minute survey. We'll check every active grant, measure your home, and give you a written quote — with no obligation to proceed.
No cost. No obligation. No pressure.