Gas Boiler to Heat Pump UK (2026 Guide)
Thinking about replacing a gas boiler with an air source heat pump? This guide explains installation costs, radiator upgrades, running costs, hot water changes, grants, and whether switching makes sense for UK homes.
• Independent UK heat pump researcher
Can You Replace a Gas Boiler With a Heat Pump?
Yes — many UK homes can successfully replace a gas boiler with an air source heat pump, including existing properties with radiators.
However, a heat pump system works differently from a traditional gas boiler. The best results usually depend on:
- Good installation design
- Correct heat pump sizing
- Reasonable insulation standards
- Suitable radiators or underfloor heating
- Lower flow temperatures
Most important thing to understand
A heat pump is not simply a “like-for-like boiler swap”. It is a lower-temperature heating system that works best when the whole setup is designed properly.
If you are still comparing brands, read our Best Air Source Heat Pumps UK guide.
How Much Does It Cost to Replace a Gas Boiler With a Heat Pump?
Most UK homeowners currently pay between £10,000 and £18,000 before grants for a full air source heat pump installation replacing a gas boiler.
With the Boiler Upgrade Scheme grant, many installations end up costing roughly £4,500–£10,500 depending on the property and upgrade requirements.
| Property Type | Typical Installed Cost | Typical Cost After Grant |
|---|---|---|
| Modern 2–3 bed home | £10,000–£13,000 | £4,500–£6,500 |
| 4-bed detached home | £13,000–£18,000 | £6,500–£10,500 |
| Older large property | £16,000+ | £9,000+ |
See our full Air Source Heat Pump Cost UK guide for a more detailed breakdown.
What Changes When You Replace a Gas Boiler?
The biggest difference is how the system delivers heat.
Gas boilers typically run at very high flow temperatures — often 65–75°C. Heat pumps work most efficiently at much lower temperatures, commonly around 35–50°C.
This means a properly designed heat pump system usually focuses on:
- Longer, steadier heating cycles
- Lower radiator temperatures
- More consistent room temperatures
- Higher overall efficiency
Homes with combi boilers usually need larger system changes because heat pumps normally require a hot water cylinder. Read our full Combi Boiler to Heat Pump Guide.
Do You Need New Radiators?
Not always — but radiator upgrades are common when replacing a gas boiler with a heat pump.
Because heat pumps run at lower temperatures, some older radiators may not emit enough heat to warm rooms properly during winter.
Many installations only require a few upgraded radiators rather than a full replacement throughout the house.
Typical upgrades include:
- Larger double-panel radiators
- Additional radiators in colder rooms
- Underfloor heating downstairs
- Smart zoning controls
Read our detailed guide: Do You Need New Radiators for a Heat Pump?
Can You Keep Existing Pipework?
Often yes.
Many UK homes can reuse large parts of their existing heating pipework, especially if the system is already reasonably modern.
However, installers may still recommend changes if:
- Pipework is undersized
- The system sludge levels are high
- Flow rates are insufficient
- The heating layout needs zoning improvements
Older microbore systems sometimes require additional assessment.
What Happens to Hot Water?
This is one of the biggest changes for homeowners switching from a combi boiler.
Most heat pump systems use a hot water cylinder rather than producing hot water instantly like a combi boiler.
This means:
- You usually need space for a cylinder
- Hot water is stored and reheated gradually
- Good system sizing becomes important for larger households
You may also want to read our guide to heat pump costs for larger homes if your property has multiple bathrooms.
Will a Heat Pump Save Money Compared to Gas?
This depends on several factors:
- Your current gas usage
- Electricity tariffs
- Insulation quality
- System design
- Flow temperatures
- Whether solar panels are installed
Gas is still relatively competitive in the UK, so heat pumps do not automatically guarantee lower bills.
However, many well-installed systems achieve strong efficiency levels and provide:
- More stable indoor comfort
- Lower carbon emissions
- Reduced reliance on fossil fuels
- Potential long-term protection from future gas price rises
Read our full guide to Heat Pump Running Costs UK.
Do Heat Pumps Work in Winter?
Yes — modern air source heat pumps are designed to operate during UK winters, including freezing temperatures.
Many systems continue working efficiently well below 0°C, although performance naturally depends on system design and insulation quality.
Cold-weather performance is often strongest with properly sized systems running lower flow temperatures continuously rather than intermittently.
Best Heat Pumps for Replacing a Gas Boiler
Some of the strongest options for UK boiler replacements currently include:
- Daikin Altherma — excellent all-round balance
- Mitsubishi Ecodan — very strong cold-weather reputation
- Vaillant aroTHERM Plus — quiet and efficient
- Viessmann Vitocal — premium controls and performance
Installer quality matters just as much as brand selection.
Compare all major systems in our Best Air Source Heat Pumps UK guide.
When Does Replacing a Gas Boiler Make Sense?
Usually a Good Fit
- Well-insulated homes
- Homes needing a new boiler anyway
- Long-term homeowners
- Properties with modern radiators
- Homes planning wider energy upgrades
Needs More Careful Planning
- Poorly insulated older homes
- Very small properties with no cylinder space
- Homes with very high heat loss
- Undersized radiator systems
- Properties expecting instant high-temperature heating
Gas Boiler to Heat Pump FAQs
Can you replace a gas combi boiler with a heat pump?
Yes. Many UK homeowners are replacing combi boilers with heat pumps, although most systems will require a hot water cylinder.
Do heat pumps work with existing radiators?
Often yes, although some radiators may need upgrading to achieve good performance at lower temperatures.
Will I still have hot water?
Yes. Heat pump systems usually store hot water in a cylinder rather than producing it instantly like a combi boiler.
Is replacing a gas boiler worth it?
For many homes, yes — especially where the boiler already needs replacing or the homeowner wants lower-carbon heating and long-term efficiency improvements.
Our Verdict
Replacing a gas boiler with a heat pump is absolutely possible for many UK homes — but the best results come from proper system design rather than simply swapping one appliance for another.
The most successful installations usually combine good insulation, sensible radiator sizing, quality controls, and experienced installers.