Choosing between an air source heat pump and a gas boiler is not just about which technology sounds newer. It affects your installation cost, running costs, comfort, hot water and what your home needs in the future.
In a London home, the answer depends on the property. A well-insulated house with some outdoor space may suit a heat pump. A home with a working gas central heating system may still be better served by a modern condensing boiler. This guide explains the key differences, so you can decide with confidence.
There is no single winner. A heat pump suits homes that are well insulated, have space for an outdoor unit and can work with lower-temperature heating, and it may qualify for a government grant. A modern gas boiler can be a simpler, lower-cost choice when your existing system is in good condition and a like-for-like replacement is all you need. A professional survey is the only reliable way to decide.
Heat Pump vs Gas Boiler at a Glance
Air source heat pump |
Gas boiler |
|
| How it works | Uses electricity to move heat from outdoor air into your home | Burns gas to heat water |
| Efficiency | Often produces around 3 units of heat per unit of electricity under good conditions | Modern condensing boilers are rated at around 90% or higher on paper |
| Hot water | Usually needs a hot water cylinder | Combi boilers heat water on demand, with no cylinder |
| Outdoor space | Needs space for an outdoor unit | None needed |
| Radiators | Works best with lower flow temperatures, so some radiators may need upgrading | Works with most existing radiators |
| Upfront cost | Usually higher, but grants may be available | Usually lower |
| Carbon emissions | Lower | Higher, as it burns gas |
What is an Air Source Heat Pump?
An air source heat pump takes heat from the outdoor air and moves it into your home. An air-to-water system sends the heat into a wet central heating system, such as radiators and a hot water cylinder. An air-to-air system releases the heat directly into rooms, like a reversible air conditioner.
A heat pump does not create heat by burning fuel. It moves heat using electricity, so it can deliver several units of heat for each unit of electricity it uses. Real-world efficiency depends on the system design, the operating temperatures and the property, so look at the design for your own home rather than the headline figure.
What is a Gas Boiler?
A modern condensing gas boiler burns gas to heat water for your radiators and taps. Air Hive UK supplies and fits combi, system and regular boilers, and offers boiler replacement, servicing and repairs for homes and businesses.
A boiler is often the simpler option if your home already has a suitable central heating system. A like-for-like replacement usually involves fewer changes than switching to a heat pump. Even so, it is worth thinking about your long-term heating needs before replacing an old boiler with another one.
Efficiency: How to Compare Fairly
Efficiency figures need careful reading.
- Boilers: A condensing boiler can reach high efficiency when it is designed and set up correctly, especially if the return water temperature is low enough.
- Heat pumps: Efficiency is shown as COP (efficiency at a given moment) or SCOP (efficiency across a whole heating season). Performance is lower on very cold days.
- Prices matter too: Electricity usually costs more per unit than gas. A system that is more efficient may not always be cheaper to run, because of the difference in energy prices.
The question for you is not which is more efficient on paper. It is what each system will cost to install and run in your own home.
Is Your Home Ready for a Heat Pump?
A professional survey is the best way to find out. Key points include:
- Heat loss: The system must be sized to your home’s real heating needs. Too large or too small can affect comfort, performance and cost.
- Insulation: Good insulation in the loft, walls and windows makes low-temperature heating work better. Many London homes, such as Victorian houses with solid walls, lose heat quickly.
- Radiators: Heat pumps usually run at lower flow temperatures than boilers, so some rooms may need bigger radiators or other changes.
- Outdoor space: The outdoor unit needs airflow and a suitable position. Think about noise, access, appearance and the distance to neighbours.
- Hot water: An air-to-water system needs a hot water cylinder, which takes up space. Combi boilers do not need one.
- Electricity supply: Your electrical supply and consumer unit may need checking or upgrading.
How Much Does a Heat Pump Cost to Install?
There is no fixed price. A project may include the outdoor unit, a hot water cylinder, controls, pipework, electrical work, new radiators and insulation improvements. The cost depends on the size of the property, access, the system size and how much of your existing system can be kept.
Government Grants: The Boiler Upgrade Scheme
The Boiler Upgrade Scheme (BUS) is available in England and Wales and is run by Ofgem. According to Ofgem, it currently provides:
- £7,500 towards air-to-water, ground source and water source heat pumps
- £2,500 towards air-to-air heat pumps, for residential properties only
- £9,000 towards air-to-water or ground source heat pumps in eligible off-gas-grid properties, from 21 July 2026 until 31 March 2027
Most London homes are on the gas grid, so the higher £9,000 grant usually will not apply. Grants are applied for by your installer, who must be MCS certified, so always ask to see their certificate and registration details before you book. Eligibility rules can change, so check the latest details on GOV.UK or the Ofgem website.
Do You Need Planning Permission?
In England, many air source heat pump installations on houses are covered by permitted development rights, so they do not need planning permission if certain conditions are met. Since 29 May 2025, the rules are more flexible: the old one-metre boundary rule has been removed, the size limit has been increased, detached houses can have up to two units and air-to-air heat pumps are included.
The main conditions include a noise limit and the use of the MCS 020(a) noise calculation. Other rules may apply if your property is:
- a flat or maisonette, which usually has different rules
- a listed building
- in a conservation area
Leasehold properties may also need permission from the freeholder. Always check the rules for your own property with your local council before you commit.
A Practical Decision Guide
A heat pump may suit you if:
- You want to reduce fossil fuel heating and carbon emissions.
- Your home can be made suitably energy efficient.
- You have a suitable place for the outdoor unit.
- You can afford a larger upfront cost, or may qualify for a grant.
- You plan to stay in the property for the long term.
- Your home can work with lower-temperature heating.
A modern boiler may suit you if:
- Your existing central heating is in good condition.
- You need a simple, like-for-like replacement.
- You have little or no outdoor space.
- You use a lot of hot water at once, or want a combi with no cylinder.
- A heat pump would need major changes to your home.
For many homeowners, a professional survey is more useful than comparing headline prices.
Air-to-Air Heat Pumps and Air Conditioning
Many modern split-system air conditioners are also air-to-air heat pumps. They heat as well as cool, which makes them popular in London homes where rooms need cooling in summer and extra heat in winter. Air Hive UK offers air conditioning installation in London, including split, multi-split and ducted systems.
An air-to-air system does not heat your hot water or radiators, so it suits a different job from an air-to-water heat pump. Whether it can replace your boiler depends on how your home is heated.
A London Homeowner Example
Imagine a London home with an older gas boiler, average insulation and several radiators. The first question should not be “Which heat pump should I buy?” It should be “How much heat does this property really need?”
A survey can look at heat loss, radiator sizes, hot water needs, where the outdoor unit could go and the electrical supply. You can then compare the cost of a new boiler with the cost and benefits of switching. If your home is a flat, a terrace or a period property, practical issues such as noise, space and permissions also matter.
Common Mistakes to Avoid
- Choosing on purchase price alone: The lowest upfront cost may not be the lowest cost over the life of the system.
- Ignoring heat loss: A heat pump must be sized correctly. Guessing the size can affect performance.
- Assuming your radiators will work as they are: Some may need upgrading for lower-temperature heating.
- Forgetting hot water: Air-to-water systems need a properly designed hot water cylinder.
- Counting on a grant without checking eligibility: BUS has rules for the property, the technology and the installer.
- Not checking the installer’s credentials: For grants, the installer must be MCS certified. For gas work, they must be Gas Safe registered.
Getting Advice From Air Hive UK
Air Hive UK is based in Hounslow and works across West London and Greater London. Our Gas Safe registered engineers offer boiler replacement and servicing in London, and our heating systems and boiler installation in London service covers radiators, controls and full central heating systems.
If you are comparing options, a survey of your home is a better starting point than a generic online quote. Contact us for friendly advice.
Frequently Asked Questions
Which is better, a heat pump or a gas boiler?
It depends on your home. Insulation, radiators, space, hot water needs and budget all matter. A heat pump can be a good low-carbon option, while a modern boiler can still make sense when your existing system is in good condition.
Can an air source heat pump replace a gas boiler?
Yes, a correctly sized air-to-water heat pump can provide heating and hot water. A survey should check heat loss, radiators, hot water needs, the outdoor unit position and the electrical supply first.
How much does a heat pump cost to install in the UK?
It depends on the system size, hot water needs, radiators, electrical work and how complex the job is. A survey gives you a realistic quote for your home.
Is the Boiler Upgrade Scheme still available in 2026?
Yes, in England and Wales. It currently offers £7,500 for air-to-water heat pumps and £2,500 for air-to-air heat pumps. Eligibility rules apply, and your installer must be MCS certified.
Do I need planning permission for an air source heat pump?
Often not for an unlisted house in England, if the permitted development conditions are met. Flats, listed buildings and conservation areas can be different, so check with your local council.
Are heat pumps suitable for London homes?
They can be, but not for every home. Insulation, heat loss, radiator sizes, outdoor space, noise and planning rules all need checking first.
Can I get a grant for a hybrid system with a heat pump and a gas boiler?
BUS grants are generally not available for hybrid systems that keep a gas boiler alongside the heat pump. Check the latest scheme rules before you plan.
Final Thoughts
The choice between an air source heat pump and a gas boiler should be made for your property, not for whichever technology sounds newer or cheaper. A heat pump can be an excellent choice for the right home. A modern boiler can still be sensible when a simple replacement is all you need.
The best first step is a proper assessment of your heat loss, insulation, radiators, hot water needs, outdoor space and budget. If you would like advice, Air Hive UK can help you compare your options.
