This comparison is most useful when you separate running cost from installation cost.
A fair gas-vs-heat-pump test compares useful heat delivered, not raw fuel units.
All figures in this article are broad estimates. Energy prices, fuel quality, installer design, weather, grants, and household habits can change the result, so use the numbers as a planning guide rather than a guarantee.
Worked example + break-even check (illustrative)
Example only: 13,000 kWh useful heat demand. Gas boiler efficiency 89%, gas price 7.2p/kWh. Annual gas fuel cost = (13,000 ÷ 0.89) × 0.072 = about GBP1,052.
Heat pump at SCOP 3.3 with electricity at 27p/kWh gives annual cost = (13,000 ÷ 3.3) × 0.27 = about GBP1,064.
In this scenario the result is effectively tied on annual fuel spend, so grants, equipment lifetime, comfort, and carbon become the practical decision drivers.
Comparison table: what usually changes the result
These are directional planning signals, not quote-level guarantees.
| Condition | Likely running-cost direction | What to verify |
|---|---|---|
| Old gas boiler + strong heat pump design | Favors heat pump | Real-world boiler efficiency, projected SCOP |
| Cheap gas tariff + high electricity tariff | Favors gas boiler | Tariff options and time-of-use eligibility |
| Upgraded emitters + lower flow temperatures | Improves heat pump economics | Design flow temp and commissioning target |
Decision checklist
Have you tested high/medium/low SCOP assumptions?
Have you priced the project net of confirmed grants?
Have you compared maintenance and repair risk for the existing boiler?
Have you linked your result to the methodology page so assumptions are transparent?
Key sources
Use Ofgem and DESNZ sources for UK market context and policy updates.
Use CRU and SEAI sources for Ireland tariff and retrofit context.
Official data can set realistic ranges, but your own tariff and meter history should drive the final calculation.
Common mistakes to avoid
- Using boiler nameplate efficiency as annual real efficiency.
- Skipping a break-even sensitivity check.
- Not separating running costs from full-lifecycle economics.
Conclusion
Gas vs heat pump can be close on annual running cost, so treat borderline outcomes carefully.
Use sensitivity ranges and keep the methodology visible when sharing results.