Gas Boiler to Heat Pump UK (2026 Guide)
Thinking about replacing a gas boiler with an air source heat pump? Understand installation costs, the £7,500 grant, radiator and hot-water changes, and how your potential running costs could compare.
- Updated for 2026
- Current grant information
- Independent homeowner advice
Can You Replace a Gas Boiler With a Heat Pump?
Yes. Many UK homes with gas central heating can switch successfully to an air-to-water heat pump, including existing properties using radiators.
But it is not normally a like-for-like appliance swap. A good conversion considers the property’s heat loss, radiator output, flow temperature, hot-water requirements, controls and the design of the whole heating system.
If you currently have a gas combi boiler, the change can be more noticeable because most air-to-water heat-pump systems use stored hot water rather than producing it instantaneously.
How Much Does It Cost to Replace a Gas Boiler With a Heat Pump?
Energy Saving Trust currently gives around £12,000 as a typical air source heat pump installation cost. Your actual quotation can be lower or higher depending on the property and the work needed to adapt the heating system.
Important cost factors include:
- Property size and calculated heat loss
- Heat-pump capacity
- Radiator or underfloor-heating requirements
- Whether a hot-water cylinder needs to be installed or replaced
- Pipework changes
- Electrical work
- Outdoor-unit location and access
- Controls and commissioning
| Cost point | Current figure |
|---|---|
| Energy Saving Trust typical air source heat pump installation | Around £12,000 |
| Standard Boiler Upgrade Scheme grant | £7,500 |
| Simple worked example using £12,000 installation cost | Around £4,500 after grant |
The £4,500 figure is simply a worked example using the Energy Saving Trust benchmark. It is not a guaranteed installation price. Your contribution depends on the actual quotation, eligibility and what work the property requires.
What Could a Heat Pump Cost for Your Home?
A national average can only take you so far. Your likely installation cost and available support depend on factors such as your property type, number of bedrooms and the heating system you are replacing.
Use our calculator to answer a few questions about your home and get a more relevant indication of the costs and grant support that may apply.
Check Your Heat Pump Costs & Grant →For a fuller explanation of installation pricing, see our Air Source Heat Pump Cost UK guide.
Compare Up to 3 Heat Pump Installers Near You
Tell us a little about your property to see installer options available in your area.
Free to use with no obligation
Can You Get the £7,500 Heat Pump Grant When Replacing Gas?
For eligible properties in England and Wales, the Boiler Upgrade Scheme currently provides £7,500 towards an air-to-water heat pump.
Replacing a mains-gas boiler does not by itself prevent you from receiving the standard £7,500 grant, provided the property and proposed installation meet the wider scheme requirements.
What about the £9,000 heat pump grant?
The temporary £9,000 level of support is different. It applies to qualifying off-gas-grid properties currently heated by oil or LPG that meet the scheme requirements.
If your home is connected to mains gas and you are replacing a gas boiler, that additional £1,500 uplift does not apply. The relevant BUS amount for an eligible air-to-water installation is normally £7,500.
See our full Heat Pump Grants UK guide for the current scheme rules.
What Changes When You Replace a Gas Boiler?
The biggest difference is not simply the appliance supplying the heat. It is how the whole heating system is designed and operated.
A heat pump generally delivers heat more gradually and works most efficiently when the home can be heated using relatively low water temperatures.
Gas boiler heating
- Existing systems may have been designed around higher water temperatures
- Can deliver relatively short, intense periods of heating
- Combi boilers can provide hot water without a cylinder
- Radiator sizes may have been selected around boiler temperatures
Heat-pump heating
- Usually performs best with lower system temperatures
- Often uses longer, steadier heating periods
- Air-to-water systems normally use stored domestic hot water
- Radiator output needs to be checked against the new design
The key point
A heat pump should be designed as a complete heating system rather than treated as a direct boiler replacement. Heat loss, emitters, flow temperature, controls and hot-water requirements all affect performance.
If you currently have a combi boiler, see our dedicated Combi Boiler to Heat Pump guide.
Do You Need New Radiators?
Not necessarily. Some existing radiators can work well with a heat pump, while others may need to be enlarged or replaced.
The important question is whether each radiator can provide enough heat for its room at the proposed system flow temperature.
You may be able to keep them when…
- Existing radiators are already generously sized
- The property has manageable heat loss
- The design works at an appropriate flow temperature
- Individual rooms already have sufficient emitter capacity
Upgrades may be needed when…
- Radiators are too small for the room heat loss
- Some rooms require substantially more heating output
- The proposed lower flow temperature reduces emitter output too far
- The existing heating system is poorly balanced or designed
It is entirely possible for an installation to keep some existing radiators while upgrading others.
Read Do You Need New Radiators for a Heat Pump? for a fuller explanation.
Compare Up to 3 Heat Pump Installers Near You
Tell us a little about your property to see installer options available in your area.
Free to use with no obligation
Can You Keep Your Existing Heating Pipework?
Sometimes. Existing pipework does not automatically need replacing because a heat pump is being installed.
The installer needs to establish whether the current system can provide the required water flow and whether its condition and layout are suitable for the proposed design.
Additional work may be recommended where:
- Pipework is too restrictive for the required flow
- Parts of the system are in poor condition
- There is significant sludge or contamination
- The existing layout causes poor hydraulic performance
- Changes are needed to accommodate new equipment
What about microbore pipework?
Microbore does not automatically make a property unsuitable for a heat pump. Its size, length, layout and the required flow rates need to be considered as part of the complete system design.
What Happens to Your Hot Water?
This can be one of the biggest practical changes, particularly if you are replacing a combi boiler.
An air-to-water heat pump normally heats domestic hot water and stores it in a cylinder rather than producing hot water instantaneously as it is used.
Cylinder space
You will normally need a suitable location for a hot-water cylinder if your property does not already have one.
Household demand
The cylinder should be sized around actual hot-water use, including household size, bathrooms and typical shower or bath demand.
Recovery
Stored hot water needs time to reheat, so system design and controls should reflect how the household uses hot water.
A properly designed installation should provide appropriate hot-water capacity for normal household use, but the cylinder should be selected for the household rather than assumed purely from bedroom count.
If you have a larger property, see our Heat Pump Cost for a 4-Bed House UK guide.
Will a Heat Pump Cost Less to Run Than Your Gas Boiler?
Not automatically. Heat pumps can deliver several units of useful heat for every unit of electricity they use, but electricity currently costs substantially more per kWh than mains gas.
For the Ofgem price-cap period from 1 October to 31 December 2026, the average Direct Debit unit rates are:
| Fuel | Average unit rate |
|---|---|
| Electricity | 26.32p/kWh |
| Gas | 7.97p/kWh |
These are national average Direct Debit price-cap rates. Your actual tariff and regional rates may differ.
Whether your heat pump costs less to run than your current gas boiler depends on factors including:
- Your current gas consumption
- The efficiency and condition of the existing boiler
- The heat pump’s seasonal efficiency
- Flow temperature
- Property heat loss
- Radiator and emitter sizing
- Hot-water use
- Controls and weather compensation
- Your electricity tariff
- Whether you continue paying a gas standing charge for another gas appliance
How Could Your Gas Boiler Running Costs Compare With a Heat Pump?
Generic averages cannot tell you whether your particular home is likely to spend more or less on heating.
Use our calculator to compare your existing heating with an air source heat pump using information about your home and current heating system.
Compare Gas vs Heat Pump Running Costs →For the methodology and a more detailed explanation of tariffs, seasonal efficiency and system design, see our Heat Pump Running Costs UK guide.
Do Heat Pumps Work in Winter?
Yes. Air source heat pumps are designed to operate in cold weather and can continue heating homes when outdoor temperatures fall below freezing.
However, available output and efficiency change as outdoor temperature changes. The system therefore needs to be sized against the property’s calculated design heat loss rather than simply selected from the nominal output of the old boiler.
Good cold-weather performance depends on the complete design, including:
- Correct heat-pump sizing
- Suitable emitters
- Appropriate flow temperatures
- Correct controls
- Good installation and commissioning
Read our detailed guide: Do Heat Pumps Work in Winter UK?
How Should You Choose a Heat Pump?
There is no single model that is automatically best for every gas-boiler replacement.
Rather than choosing on brand name alone, compare:
System design
The proposed unit needs to suit the property’s heat loss, emitter design and hot-water requirements.
Operating temperatures
Understand the proposed design flow temperature and how it affects radiator output and efficiency.
Noise and siting
Consider outdoor-unit sound characteristics and whether the proposed position is suitable for the property.
Controls
Appropriate controls and weather compensation can help the system maintain stable and efficient operation.
Warranty and support
Check the manufacturer’s current warranty requirements and what support is available through the installer.
Installation quality
Good design, commissioning and installation can matter at least as much as choosing between reputable brands.
See our Best Air Source Heat Pumps UK comparison for a dedicated look at current systems.
When Does Replacing a Gas Boiler With a Heat Pump Make Sense?
Often worth investigating when…
- Your boiler is already approaching replacement
- The home has manageable heat loss
- Radiators can provide enough output at suitable temperatures
- You have or can create space for required hot-water equipment
- You qualify for the Boiler Upgrade Scheme
- You want to move away from fossil-fuel heating
Needs more careful planning when…
- The property has particularly high heat loss
- There is little space for a hot-water cylinder
- Existing emitters are substantially undersized
- Major pipework changes may be required
- Your main objective is a guaranteed reduction in energy bills
- The proposed design relies on high flow temperatures without explaining the efficiency implications
For a broader assessment of the pros and cons, read Are Heat Pumps Worth It?.
Compare Up to 3 Heat Pump Installers Near You
Tell us a little about your property to see installer options available in your area.
Free to use with no obligation
Gas boiler to heat pump FAQs
Can you replace a gas combi boiler with a heat pump?
Yes. A gas combi boiler can be replaced with an air-to-water heat pump, although the new system will normally need stored hot water, so space for an appropriate cylinder is an important consideration.
How much does it cost to replace a gas boiler with a heat pump?
Energy Saving Trust currently gives around £12,000 as a typical air source heat pump installation cost. Eligible properties in England and Wales can currently receive £7,500 through the Boiler Upgrade Scheme. Your actual quotation depends on the property and the heating-system changes required.
Do heat pumps work with existing radiators?
Often, yes. Each radiator should be checked against the room’s calculated heat loss and the proposed system flow temperature. Some may already be suitable while others may need upgrading.
Will I still have hot water?
Yes. Most air-to-water heat-pump systems heat domestic hot water and store it in a cylinder. The cylinder should be sized around the household’s expected demand.
Is a heat pump cheaper to run than a gas boiler?
Not necessarily. The result depends on factors including your existing gas use, boiler efficiency, the heat pump’s seasonal efficiency, flow temperature, electricity tariff, heat loss and hot-water demand. Our calculator can help you compare the two using information about your own home.
Can I get the £7,500 grant if I currently have gas?
Eligible properties in England and Wales can currently receive £7,500 towards an air-to-water heat pump through the Boiler Upgrade Scheme. The temporary additional £1,500 support applies to qualifying off-gas-grid properties currently heated by oil or LPG, not mains-gas boiler replacements.
Related guides
Combi Boiler to Heat PumpSee what changes when moving from instantaneous hot water to a heat-pump system.
Air Source Heat Pump Cost UKUnderstand installation costs and the main factors that can change your quotation.
Heat Pump Grants UKCheck the current support available for eligible heat-pump installations.
Heat Pump Running CostsUnderstand tariffs, seasonal efficiency and the factors affecting actual heating costs.
Do You Need New Radiators?Learn how radiator sizing and flow temperature can affect a boiler-to-heat-pump conversion.
Best Air Source Heat Pumps UKCompare current systems and the factors that matter when choosing an air source heat pump.
Sources and verification
This guide uses current UK information from primary and established consumer-energy sources. Grants, installation costs and energy prices can change, so check current information before making a financial decision.