HeatPumpHeat Pump vs Gas Boiler — An Honest Comparison
You'll find plenty of sites claiming heat pumps are always better — or that gas boilers are still the smart choice. The truth is more nuanced. The right answer depends on your home, your budget, and your electricity tariff. Here's the honest head-to-head.
Head-to-Head Comparison
| Factor | Heat Pump (ASHP) | Gas Boiler | Winner |
|---|---|---|---|
| Upfront cost | £10,000 (after £7,500 BUS grant) | £2,000 – £3,000 | Gas boiler |
| Running cost (standard rate) | ~£918/yr | ~£884/yr | Draw |
| Running cost (off-peak tariff) | £281 – £375/yr | ~£884/yr | Heat pump |
| Annual maintenance | £100 – £200/yr | £60 – £100/yr | Gas boiler |
| Lifespan | 20 – 25 years | 12 – 15 years | Heat pump |
| Carbon emissions | ~75% lower than gas | ~2.7 tonnes CO2/yr | Heat pump |
| Heating comfort | Slow, steady, even warmth | Fast, on-demand heat | Depends on preference |
| Hot water | Needs cylinder (no instant) | Combi = instant, no cylinder | Gas boiler (convenience) |
| Government support | £7,500 BUS grant + 0% VAT | None (likely restrictions coming) | Heat pump |
| Future-proofing | Aligned with net zero targets | Phase-out expected late 2020s | Heat pump |
Total Cost of Ownership Over 20 Years
Upfront cost only tells part of the story. When you factor in running costs, maintenance, and replacement, the long-term picture shifts:
| Cost Element | Heat Pump (20yr) | Gas Boiler (20yr) |
|---|---|---|
| Installation | £10,000 (after grant) | £2,500 + £2,500 (replacement at yr 13) |
| Running costs (off-peak) | £375 x 20 = £7,500 | £884 x 20 = £17,680 |
| Maintenance | £150 x 20 = £3,000 | £80 x 20 = £1,600 |
| 20-year total | £20,500 | £24,280 |
On an off-peak tariff, the heat pump saves roughly £3,780 over 20 years — and you haven't needed a replacement. At the standard electricity rate, the numbers are closer: about £28,360 for the heat pump vs £24,280 for gas, making gas cheaper by around £4,000 over two decades.
Key insight: The electricity tariff is the single biggest factor in whether a heat pump saves you money. On standard rate, gas wins on running cost. On off-peak, heat pump wins convincingly. See our running costs guide for the full tariff breakdown.
When a Heat Pump Is the Right Choice
- You're off the gas grid: If you're on oil, LPG, or electric heating, a heat pump almost always saves money. The comparison isn't even close — see our heat pump vs oil boiler guide.
- Good insulation: Well-insulated homes (cavity walls, 270mm loft insulation, double or triple glazing) need smaller heat pumps and get better efficiency. If your EPC is C or above, you're in good shape.
- Off-peak electricity tariff: Economy 7, Octopus Cosy, or Octopus Agile make heat pumps significantly cheaper to run than gas. This is the number one lever for running cost savings.
- Long-term view: If you plan to stay in your home for 10+ years, the lower running costs and longer lifespan make a heat pump the better financial investment.
- Environmental priority: A heat pump cuts your heating carbon footprint by roughly 75%. As the electricity grid gets cleaner, this gap will widen further.
- New build or major renovation: If you're already doing significant building work, adding a heat pump is far cheaper and less disruptive than a standalone retrofit.
When a Gas Boiler Still Makes Sense
We're not going to pretend heat pumps are right for everyone. Here's when gas might be the more practical choice:
- Poor insulation and no budget to improve it: A heat pump in a draughty, single-glazed house will need to be oversized, expensive to buy, and expensive to run. Insulate first, then reconsider.
- Very tight budget: A new gas boiler costs £2,000-£3,000. Even with the BUS grant, a heat pump is £2,500-£7,500 out of pocket. If cash flow is your primary constraint, a gas boiler buys you time.
- You cannot get an off-peak tariff: Without off-peak electricity, heat pump running costs are roughly the same as gas. The financial case weakens significantly.
- Near retirement age in a short-stay home: If you're planning to sell within 5 years, you may not recoup the higher upfront cost — though a heat pump can add to property value.
- No space for a hot water cylinder: Heat pumps need a cylinder for hot water. If you currently have a combi boiler and literally cannot fit a cylinder, a gas replacement may be more practical.
Reality check: Gas boilers are a mature, reliable, well-understood technology. There is nothing wrong with replacing a broken gas boiler with a new one if your circumstances don't suit a heat pump right now. But if your boiler has 5+ years of life left, start planning for a heat pump — the transition is easier when you have time to insulate and research.
The Comfort Difference
This is something most comparison sites ignore, but it matters for daily life:
Gas boilers heat up fast. You turn the thermostat up and feel warmth within 15-20 minutes. The flip side: the temperature cycles — warm, then cooling, then the boiler fires again. Some people find this uncomfortable.
Heat pumps heat slowly and steadily. Most are designed to run almost continuously at low output, maintaining an even temperature 24/7. There's no "blast of heat" — instead, the house stays at a consistent, comfortable temperature. Many heat pump owners say their home feels more comfortable than with a gas boiler, but it requires a mindset shift: you leave the system on and let it manage itself rather than turning it on and off.
The key difference with hot water: a gas combi boiler gives you instant, unlimited hot water. A heat pump heats a cylinder, which takes 1-2 hours to reheat once depleted. For most households this is fine — a 200-litre cylinder provides 2-3 baths or several showers. But large families who use enormous amounts of hot water may need to plan slightly more.
Related Guides
Running Costs
Full tariff-by-tariff breakdown of annual running costs.
Installation Costs
How much a heat pump costs to install in 2026.
BUS Grant Guide
Get £7,500 towards your heat pump.
Heat Pump vs Oil Boiler
If you're on oil, this one's a no-brainer.
Frequently Asked Questions
Is a heat pump worth it if I have mains gas?
It depends on your situation. If you can get an off-peak electricity tariff and your home is reasonably insulated, a heat pump will save money over its 20-year lifespan. If you are on a tight budget, your home is poorly insulated, and you cannot switch tariff, a new gas boiler may be more practical in the short term — though gas boiler sales will eventually be restricted.
Will gas boilers be banned?
The UK government plans to phase out new gas boiler installations in new-build homes from 2025 and is expected to introduce restrictions on gas boiler replacements in existing homes during the late 2020s. However, a complete "ban" is unlikely — more probable is a combination of incentives (grants, tariffs) and regulations that make heat pumps the default choice.
Can I switch from a gas boiler to a heat pump?
Yes. Most homes with existing gas central heating (wet radiator systems) can switch to an air source heat pump. The process typically takes 2-5 days. You may need some radiator upgrades and a hot water cylinder, but the existing pipework is usually reusable.
How noisy is a heat pump compared to a gas boiler?
Modern air source heat pumps produce 40-55 dB at 1 metre — similar to a fridge or quiet conversation. They are virtually silent indoors. Gas boilers produce 40-50 dB, so the difference is minimal. Ground source heat pumps are even quieter as the compressor is indoors. See our heat pump noise guide for details.
What about hydrogen boilers?
The UK government has scaled back hydrogen heating plans. The hydrogen village trials in Redcar and Ellesmere Port were both cancelled. While hydrogen-ready boilers are being sold, a national hydrogen heating network is now considered unlikely. Heat pumps are the government-backed solution for decarbonising home heating.