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Air Source Heat Pumps

An air source heat pump is an increasingly popular way of heating your home. It absorbs heat from the air outside and transfers it into your home using electricity. You can use this to heat your space through your central heating system or heat water stored in a hot water cylinder for all your daily needs.

Air Source Heat Pumps

They generate heat at lower temperatures than traditional gas and oil boilers, so you will have to run them for longer periods to heat your home to your chosen temperature. Additionally, having a well-insulated home is advisable to ensure the heat produced by the pump doesn’t leak out.

That said, an air source heat pump could save you sizeable amounts on your heating bill in the long run. It enables you to generate your own renewable heat all year-round, thus lowering your home’s environmental impact, and can reduce your energy bill by up to £240 per year.

In this article, we will ascertain how an air source heat pump works and assess the potential advantages and disadvantages of installing one in your property.

What is an air source heat pump?

An air source heat pump is a heating system that extracts heat from the outside air, increases its temperature using a compressor, and transfers it into the heating system within your home.

It works as follows:

  1. 1
    The air source heat pump extracts heat from the outside air using a refrigerant that absorbs the heat as it passes through the outdoor unit's evaporator coil.
  2. 2
    The refrigerant, now warmed, is compressed by the pump, which raises its pressure and temperature further
  3. 3
    Heat Distribution: The warmed, high-pressure refrigerant is then transferred to your heating system where it condenses and releases heat. This heat is used to warm radiators, power an underfloor heating system, and heat water inside a hot water cylinder. Stored hot water can be used in showers, baths, and taps.

While heat pumps will increase your electricity bill, they produce more heat in kWh than they use in electricity, making them an energy efficient method of heating your home. Conversely gas boilers, especially those installed before 2005, use more energy than they emit into your home. This makes them a far less energy efficient way of heating your home.

Types of air source heat pumps

There are two primary types of air source heat pump: air-to-water and air-to-air. They function in different ways and are compatible with different kinds of heating systems.

Air-to-water

Air-to-water heat pumps extract heat from the outside air and apply it to stored water which can then be used to warm radiators, power underfloor heating or for domestic water needs.

They’re better suited to homes with large radiators or water underfloor heating as they produce less heat than a conventional boiler. As such, they require a medium with a larger surface area to produce heat effectively.

Air-to-air

Air-to-air heat pumps take heat from the outside and release it into your home via a fan system. While these effectively circulate warm air around your home, you will need a separate water-heating system to produce hot water.

In summer, air-to-air heat pumps can be used as cooling systems. They can absorb warm air from outside and transfer it into cool air for your home.

How efficient are air source heat pumps?

Air source heat pumps are efficient heating systems that are capable of producing more energy than they consume.

Their efficiency is measured by calculating their co-efficient of performance (COP). This is done by comparing the heat output from the condenser to the power supplied by the compressor.

Air source heat pumps can yield COPs of 2 to 4, which means for every 1 kWh of electricity used, they produce 2 to 4 kWh of heat. This makes them far more efficient than traditional electric heaters.

In colder weather, an air source heart pump performs less efficiently, as there is less heat in the air to absorb. However, they remain more efficient than electric heating.

How much does an air source heat pump cost?

When calculating the cost of an air source heat pump, several factors need to be considered, including the initial cost of equipment and installation, the operating costs, and maintenance costs.

Initial cost of installation

Upfront costs of installation will be your biggest outlay, with the average air source heat pump installation coming in at around £11,000. The overall cost of installation depends on the size of the heat pump, the size of your property, the status of the building (e.g., whether it is a listed property or a new-build), and how many alterations you need to make to the way you currently heat your property.

operating costs

Operating costs depend on the design of your air source heat pump and how your heating system operates. Factors such as the size of your property, the cost of your electricity (per kWh), and the overall COP of your heat pump.

Using the typical electricity price of 30p/kWh and assuming a COP of 3, your annual bill would come to:

  1. 1
    roughly £700-800 for a 1-bedroom house
  2. 2
    roughly £950-£1,100 for a 2-bedroom house
  3. 3
    roughly £1,300-£1,450 for a house with 4+bedrooms

maintenance costs

An annual service of your air source heat pump will cost between £100 and £300. This may go up if you require replacement parts. Yearly checks are recommended to ensure your pump is functioning correctly and to prevent expensive repairs.

Are there any grants for air source heat pumps?

An air source heat pump is a sizeable financial investment, but thankfully there are some heat pump grants available in the UK. These are limited to one grant per property.

  1. 1
    If you live in England and Wales, you can get £7,500 towards the cost of an air source heat pump through the Boiler Upgrade Scheme.
  2. 2
    For those in Scotland, grants, interest-free loans, or a combination of both are available for the installation of heat pumps. £7,500 is available in grant funding, with an additional £7,500 available as an interest-free loan.
  3. 3
    Northern Irish residents aren’t currently eligible for any grants.

To qualify for a grant, you must own the property you’re seeking to install an air source heat pump in and must be replacing a pre-existing fossil fuel heating system.

You cannot get a grant for a hybrid heat pump system, e.g. a combination of an air source heat pump and a gas boiler. There are certain standards, such as minimum efficiency levels, that your air source heat pump must meet for you to receive your grant. Your installer can advise you on these during the process.

You also cannot get a grant for:

  • Social housing

  • Most new-build properties

  • A property that has already benefitted from government funding for a heat pump or biomass boiler

Do air source heat pumps save you money?

Yes, air source heat pumps can save you money, particularly if you are switching from traditional heating systems like oil, electric, or LPG boilers. Air source heat pumps are highly efficient, producing 2 to 4 kWh of heat for every 1 kWh of electricity consumed. This high efficiency means that, despite a unit of electricity being more expensive than a unit of gas, the overall energy use can be lower.

Exactly how much you save depends on several factors including your air source heat pump’s COP, your electricity rates, and your energy consumption habits.

Additionally, if you are eligible for a grant, that can cover over 70% of the cost of installing your air source pump. This saving combined with the lower operational cost than traditional heating systems means air source heat pumps can save you significant sums of money in the long term.

Is an air source heat pump worth it?

When considering whether to install an air source heat pump, there are several pros and cons to consider:

Pros

  • Effort required during initial installation
    Installing your first air source heat pump is a lot more work than simply replacing your gas boiler. It requires meticulous planning to ensure you reap the benefits. Together with an experienced installer, you must carefully design your heating system and make accurate heat loss calculations to maximise your energy efficiency and minimise your outgoings.
  • Initial cost
    The initial cost of an air source heat pump is not cheap. You can spend up to £15,000 on the installation of your heat pump, while traditional gas boilers cost up to £5,000 to install.
  • Space
    Air source heat pumps require sufficient space outside your home for the external condenser unit. Additionally, you may require indoor space for a hot water cylinder if you choose to heat your water with your air source heat pump. While space is no problem for larger houses with gardens, it can be a stumbling block for people in smaller properties.
  • Lower heat output
    As air source heat pumps produce heat at lower temperatures than gas or oil boilers, you may require larger radiators to get the best out of them. Additionally, you will get better results if your property is well insulated otherwise your property will lose heat rapidly during colder months.
  • Noise
    Some heat pumps can be noisy, like the sound of an air conditioner or heavy rain. While newer models are usually quieter, noise is still a consideration for any prospective purchaser.

What size air source heat pump do I need?

The size of your air source heat pump depends on several factors including the size of your property and how well insulated it is.

Air source heat pumps usually have heat outputs between 5kW and 16kW.

A 100m² property will require a 5kW air source heat pump, while a 200m² property would need a 10kW heat pump. The larger the square footage, the larger the heat pump required.

If your home is well-insulated, it will require less heat energy to maintain the desired temperature. Whereas a poorly insulated property will need a larger heat pump than a well-insulated home with the same square footage.

Other factors such as single-glazed windows and doors, the number of occupants, external climate, and ceiling height can all influence the size of air source heat pump required.

Performing the appropriate calculations alongside an experienced installer can help you decide what size heat pump is appropriate for your space.

Do air source heat pumps work with radiators?

Yes, air source heat pumps work with radiators. You may not need to change your existing radiators when installing your air source heat pump. However, the pipework will most likely require changing.

Also, be mindful that due to the lower heat output of air source heat pumps, investing in larger radiators can help you achieve your home’s desired temperature more efficiently.

It is a misconception that only properties with underfloor heating are suited to heat pumps. Your heat pump engineer will be able to inform you immediately whether your existing radiators can work with a heat pump.

Do air source heat pumps work in winter?

Yes, air source heat pumps can work in winter. While they are most efficient in warm climates, they can still work effectively in colder conditions. In fact, the average air source heat pump has minimum working temperatures of between -10°C and -25°C.

Given the UK’s relatively mild winter climate, external temperatures are not a deal-breaker when it comes to air source heat pumps.

How much does it cost to install an air source heat pump?

An air source heat pump can cost anywhere between £3,000 and £15,000 to install. You may be eligible for a £7,500 grant under the Boiler Upgrade Scheme, so it’s worth checking your eligibility.

While the upfront costs of installation are sizeable, you can save hundreds on your energy bill in the long term.

Are air source heat pumps noisy?

While noise is experienced subjectively, air source heat pumps do generate some noise, particularly from the outdoor unit's fan and compressor.

However, modern models are designed to be much quieter than older versions. Noise levels typically range between 40 and 60 decibels, comparable to the sound of a refrigerator or a normal conversation. Placement of the unit and proper installation are crucial to minimizing noise.

Additionally, some manufacturers offer specific models designed for noise-sensitive spaces. Overall, while not completely silent, most well-installed ASHPs won’t cause significant disturbance.

Do air source heat pumps need servicing?

Yes, air source heat pumps require regular servicing to maintain efficiency and longevity. Annual maintenance is recommended, which includes cleaning filters, checking refrigerant levels, inspecting electrical connections, and ensuring the outdoor unit is free of debris.

Proper servicing helps prevent breakdowns, improves energy efficiency, and extends the lifespan of the system. While some tasks, like cleaning filters, can be done by homeowners, a professional technician should be called in to assess your air source heat pump’s condition.

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Activity History - Last updated: 10 November 2025, Published date:

Reviewer

Mike Rowe

Energy Expert

Mike is a recognised leader in the UK energy sector with over two decades of experience, having run one of the country's most trusted Ofgem-accredited energy comparison platforms before selling in 2019. Today, he advises EnergyComparison.co.uk and works with businesses on the transition to net zero.

Activity History - Expert Reviewed on 11 November 2025 and last checked on 10 November 2025