Heat Pump Boiler: Replacing Your Boiler With a Heat Pump
A heat pump boiler does the same job as a gas or oil boiler. It heats your radiators, underfloor heating and hot water. The difference is that instead of burning fuel, a heat source pump moves warmth out of the outside air and into your home, which is why it is far more efficient. Most UK homes replace their boiler with an air source heat pump costing £8,000 to £14,000 fitted, and the £7,500 Boiler Upgrade Scheme grant takes a big chunk off.
Quick Answer
A heat pump boiler is a heat pump fitted in place of a gas or oil boiler. It heats your radiators and hot water by drawing warmth from the outside air rather than burning fuel, producing about 3 to 4 units of heat per unit of electricity. A typical install costs £8,000 to £14,000, or £500 to £6,500 after the £7,500 Boiler Upgrade Scheme grant.
Prices as of early 2026, based on UK MCS-certified installer quotes.
Fact-checked by John Rooney, Solar Energy Editor. Editorial policy
What is a heat pump boiler?
Strictly speaking there is no such thing as a "heat pump boiler". People use the phrase because they want the thing that replaces their boiler and does what their boiler did. That thing is a heat pump. In nine out of ten UK homes it is an air source heat pump, sometimes called an air heat pump or a heat source pump.
A gas boiler burns fuel to make heat, so it can never give back more energy than it uses. A heat pump does not make heat, it moves it. A fan draws in outside air, a refrigerant absorbs the warmth even on a cold day, and a compressor concentrates that warmth and passes it to your heating system. Because it is moving energy rather than burning it, a good heat pump delivers 3 to 4 units of heat for every unit of electricity it uses. A gas boiler at its best returns about 0.9 units of heat per unit of gas.
For your day to day life nothing much changes. You still set a thermostat, you still get hot water from a tap, and the unit indoors looks broadly like the cylinder and controls you already have. The only visible difference is a unit outside the house, similar in size to an air conditioning condenser.
Heat pump vs a gas boiler
The headline trade is a higher upfront cost for lower running costs, far lower carbon, and a system that lasts longer. The table below sets the two side by side.
| Gas Boiler | Heat Pump | |
|---|---|---|
| Efficiency | Up to ~92% | 300–400% (SCOP 3–4) |
| Upfront cost | £2,000–£3,500 | £8,000–£14,000 (£500–£6,500 after grant) |
| Grant available | None | £7,500 Boiler Upgrade Scheme |
| Typical lifespan | 10–15 years | 15–20 years |
| Flow temperature | 60–70°C | 35–50°C (steady, gentle heat) |
| Carbon | High (burns fossil fuel) | Low, and falls as the grid greens |
The lower flow temperature is the main thing that makes a heat pump feel different. It heats your home with a steadier, gentler warmth rather than short bursts of very hot water. To deliver that comfort some homes need one or two radiators upsized, which a heat loss survey identifies. For a full money comparison see heat pumps vs boilers.
Hybrid heat pump and boiler systems
A hybrid system keeps your existing gas or oil boiler and adds a smaller heat pump alongside it. The heat pump does most of the heating across the year, and the boiler steps in only on the coldest days or for a fast hot water boost. It is a genuine middle ground for homes that are not yet insulated well enough to run on a heat pump alone, or where a full radiator upgrade is not practical right now.
The trade-off is that you keep a fossil fuel bill and a second appliance to maintain, and from 2026 hybrid installs are not eligible for the full £7,500 Boiler Upgrade Scheme grant in the way a standalone heat pump is. For most homes a properly sized standalone heat pump is the better long term answer, but a hybrid can be a sensible stepping stone.
What does it cost to swap a boiler for a heat pump?
A typical air source heat pump runs £8,000 to £14,000 fully installed in 2026. Where you land depends on the size of your home, the brand, and whether your radiators or hot water cylinder need upgrading. The £7,500 Boiler Upgrade Scheme grant is taken off by your installer at the point of install, so most homes pay £500 to £6,500 net.
| Home Size | Heat Pump Size | Cost Before Grant | Net After £7,500 Grant |
|---|---|---|---|
| 1–2 bed flat or small house | 4–6 kW | £8,000–£10,000 | £500–£2,500 |
| 3 bed semi (typical) | 6–8 kW | £9,000–£12,000 | £1,500–£4,500 |
| 4–5 bed detached | 8–12 kW | £11,000–£14,000+ | £3,500–£6,500+ |
For the full breakdown including running costs against gas, oil and LPG, see our heat pump cost guide and the heat pump grants you can claim.
Will it be cheaper to run?
For most homes leaving oil, LPG or electric heating, yes. A 3-bed home spends roughly £700 to £1,100 a year running a heat pump, dropping to £500 to £900 on a specialist heat pump tariff such as the Cosy Octopus tariff. Against mains gas the gap is narrower and depends on your home, but good insulation and a correctly sized system tip it in the heat pump's favour, and pairing with solar panels lowers the bill further. Whether it stacks up for your home comes down to insulation and sizing, which is covered in are heat pumps worth it.
Heat Pump Boiler FAQ
What is a heat pump boiler?
A heat pump boiler is a heat pump fitted to replace a gas or oil boiler. It heats your radiators, underfloor heating and hot water by drawing warmth from the outside air rather than burning fuel. It produces about 3 to 4 units of heat per unit of electricity, compared with under 1 unit from a gas boiler.
Can a heat pump replace my gas boiler?
Yes. A correctly sized air source heat pump can fully replace a gas or oil boiler in most UK homes, heating both your home and hot water. It works best in homes insulated to EPC C or better with correctly sized radiators. A heat loss survey confirms whether any radiators need upgrading.
Is a heat source pump the same as a heat pump?
Yes. Heat source pump and air heat pump are everyday names for an air source heat pump. They all describe the same appliance that moves warmth from the outside air into your heating system instead of burning fuel.
What is a hybrid heat pump boiler?
A hybrid system keeps your existing gas or oil boiler and adds a smaller heat pump. The heat pump does most of the heating across the year, and the boiler steps in only on the coldest days. It suits homes that are not yet ready to run on a heat pump alone, though it keeps a fossil fuel bill and is not eligible for the full £7,500 grant the way a standalone heat pump is.
How much does it cost to swap a boiler for a heat pump?
An air source heat pump costs £8,000 to £14,000 installed in the UK. After the £7,500 Boiler Upgrade Scheme grant, most homes pay £500 to £6,500 net. A typical 3-bed semi needs a 6 to 8 kW unit costing £9,000 to £12,000 before the grant.
Is a heat pump cheaper to run than a gas boiler?
For homes leaving oil, LPG or electric heating, almost always. Against mains gas the gap is narrower and depends on insulation and sizing, but a well-designed system on a heat pump tariff such as Cosy Octopus, ideally paired with solar, runs cheaper than a gas boiler for many homes.
Do I need new radiators to replace my boiler with a heat pump?
Often not all of them. Heat pumps run at a lower flow temperature than boilers (35 to 50°C versus 60 to 70°C), so some radiators may need upsizing to give the same warmth. A heat loss survey determines which, if any, need changing. High-temperature heat pumps can run up to 75°C for older setups.
Still weighing it up? See whether heat pumps work in winter, how noisy they are, and what installation involves.
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Related Guides
Heat Pump vs Boiler
Cost, running costs, lifespan and carbon compared, plus hybrids.
Air Source Heat Pumps
Cost, best brands, running costs, and pros and cons for UK homes.
Heat Pump Cost
Full price breakdown by type and home size, plus running costs.
Are Heat Pumps Worth It?
Honest verdict by home type, running costs, payback and pros and cons.
Heat Pump Grants
The £7,500 Boiler Upgrade Scheme, Scotland grants, and 0% VAT.
Heat Pump Installation
The process, timeline, and cost of installing a heat pump.
Heat Pumps
Air source & ground source heat pumps: costs, BUS grant up to £7,500.
Sources
- GOV.UK: Boiler Upgrade Scheme (BUS)
- Energy Saving Trust: Air Source Heat Pumps
- MCS: Certified Products & Installers
Last updated: July 2026
John Rooney is the founder of Solar Info and has been covering the UK solar energy market since 2023. He researches every battery and inverter brand against manufacturer datasheets, MCS and Ofgem data, and feedback from the MCS-certified installers in our directory before publishing.
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