The Complete Guide to Air Source Heat Pumps

As the government looks to eliminate traditional gas and oil boilers, air source heat pumps are one of the leading eco-friendly alternatives to consider.

But with most UK homeowners more familiar with boilers, air source heat pumps can be confusing to get to grips with.

The WhatPrice team is here to demystify air source heat pumps (ASHPs) before you take the plunge and purchase one.

In this post, we’ll explain what ASHPs are, how much they cost and what you should expect if you plan on relying on one to heat your home.

What is an air source heat pump?

An air source heat pump (ASHP) is a low-carbon heating system. It works by extracting heat from the outside air to heat your home and in some cases, your heat hot water too.

Many people compare ASHPs to how a fridge works but in reverse. That’s because instead of taking heat out of the fridge, an air source heat pump draws heat out of the air and uses it to heat your home. The clever technology is extremely efficient, to the point that an air source heat pump can even extract heat from the outside air during cold spells.

There are several well-known brands which serve the air source heat pump market in the UK including Daikin, Grant, Hitachi, LG, Mitsubishi Electric, NIBE, Samsung and Vaillant.

Various heat pump types and also sizes exist, even within the air source category of the market.

However, something that all newly installed ASHPs have in common is their excellent efficiency. Overall, it is thought that air source heat pumps emit 70% less carbon emissions than a gas boiler. As well as being far greener, this can also save you money too.

How does it work?

The idea behind air source heat pumps is that they make use of heat that exists within the outside air by transferring this to the inside of our home. Depending on the ASHP type, this can mean supplying your heating, hot water and underfloor heating directly from this extracted outside heat.

Air source heat pumps are classed as low-carbon and renewable energy systems. For every 1 kWh of electricity used, a modern ASHP can generate 3-4 kWh of heat.

Unlike boilers which can often raise the indoor temperature quickly with bursts of heat, air source heat pumps provide a more ambient and consistent level of heating. While this can take some getting used to, a major advantage of switching to a heat pump is the ability to get off the gas network.

What is the difference between air-to-air and air-to-water systems?

When you’re new to heat pump technology, understanding the different types can be confusing.

The main thing you need to know is that there are two different types of air source heat pumps including air-to-air and air-to-water systems.

How these systems differ is based on how they distribute heat throughout your home, and also the type of heating they provide.

We’ve summarised the main differences here:

Air-to-air heat pumps

• Extracts heat from outside air
• Does not provide hot water
• Can also provide air conditioning
• Cheaper and simpler to install
• Ideal for open plan or small properties
• Less suitable for homes with wet heating systems

Air-to-water heat pumps

• Extracts heat from outside and transfers it to water
• Can heat radiators, hot water and underfloor heating
• Often replaces a boiler in most cases
• Requires a hot water cylinder
• Doesn’t provide air conditioning
• More expensive to install

If you’re thinking of getting an ASHP, it’s good to research each type to help select the best air source heat pump for your property and overall usage needs.

Is an air source heat pump right for my home?

Air source heat pumps are a modern way of heating your home. But as for whether an ASHP will be suitable, this will depend on the age of your property. Plus, its size, insulation levels and any existing plumbing features.

Property types best suited for heat pumps

• New build properties
• Renovated properties which now benefit from excellent insulation
• Off-grid properties
• Homes with underfloor heating

The most suitable properties for heat pumps are those which are either newly built, or have received significant upgrades to modernise them.

If your property doesn’t meet the required criteria, it will require upgrades before a heat pump can be installed.

Space and location requirements

Your property will need to accommodate an outdoor condenser unit and an indoor hot water cylinder. In some cases, the outdoor unit can be wall mounted which can provide a solution for flats or smaller homes.

Integration with existing heating systems

Air source heat pumps are compatible with:

• High output/double panel radiators
• Hot water cylinders
• Smart controls
• Solar panels
• Underfloor heating

Overall, heat pumps are a modern way of heating your home and hot water. Therefore, older or inefficient properties are more likely to require upgrades to ensure your system is compatible.

It’s also worth noting that you don’t have to get underfloor heating installed if you get a heat pump. However, underfloor heating is extremely compatible with heat pump technology.

Advantages and disadvantages of air source heat pumps

Thinking of switching to an air source heating system?

We’ve covered some of the top benefits and considerations you should know about before you go ahead.

Benefits of switching to a heat pump

Heat pumps are environmentally friendly: Air source heat pumps extract heat from the air outside your property, which is a far greener way of heating your home than traditional fossil fuels.

Lower energy bills: Heat pumps have lower running costs compared with a traditional gas boiler. Getting off the gas network means you won’t have to worry about the rising prices of gas anymore.

Safer than gas: Gas boilers can present risks such as explosion or carbon monoxide poisoning. Heat pumps don’t run on gas and also don’t require combustion to work, making them much safer for your property.

Embraces the future: Technology continues to evolve and there will come a point when boilers become obsolete, especially as gas boilers are already being phased out. Switching to a heat pump now helps future-proof your property.

Can offer heating and cooling: Model dependent, many heat pumps are capable of working in reverse meaning they can heat as well as cool your home.

Can boost property value: Our research has found that adding a heat pump to your home can boost its value from between 1%-10%.

Common drawbacks and limitations

Higher upfront cost: Priced between £11,000 to £16,000, air source heat pumps are considerably more expensive than a traditional boiler. However, various grants are available which can greatly reduce the cost of getting a heat pump installed.

Unsuitable for poorly insulated properties: ASHPs will struggle if your home’s energy efficiency hasn’t been upgraded. That said, measures such as loft insulation, thermal rendering or new windows can lower your energy bills regardless.

You may also need to replace your radiators and pipework: Heat pumps require compatible radiators and pipework to work properly. If upgrades to the rest of your system are needed, this will increase the cost.

It’s more complicated to install a heat pump than a boiler: Installing a heat pump for the first time is a considerable undertaking. It takes a small team up to 5 days to complete.

You need enough space: Air source heat pumps will require a hot water cylinder if your property doesn’t already have one (i.e. if you’re switching from a combi boiler). The external condenser unit needs to be installed outside, which may be an issue for smaller properties without adequate space.

Heat pumps are a learning curve: You will need to familiarise yourself with all of the controls and get comfortable adjusting the settings.

Noise, aesthetics and performance concerns

It used to be the case that heat pumps were noisy. However, modern heat pumps have been improved so that they operate at much quieter levels. The typical noise produced by a heat pump is between 40dB and 60dB.

To give an idea of this noise level, a pile of leaves rustling produces around 20dB. The noise levels produced by fireworks can be up to 140dB.

So when understanding the noise levels of an ASHP, a good comparison is the hum of a fridge which isn’t considered loud. Additional measures can also be taken to reduce the noise, including choosing a strategic installation location or adding some acoustic treatment around the outdoor unit.

Where performance is concerned, heat pumps are designed to offer gradual yet continual heat throughout your home, rather than the sudden bursts of heat like a boiler. Air source heat pumps also represent the very latest in heating technology, meaning they are designed to offer exceptional performance and overall reliability.

How efficient are air source heat pumps?

The whole reason why heat pumps came to be is that a more efficient and greener way of heating our homes was needed.

Modern gas combi boilers can be up to 94% efficient. If you think that sounds impressive, air source heat pumps can offer a whopping 300%-400% efficiency.

Overall, heat pumps are 3-5 times more efficient than gas boilers because they work in a different way. Crucially, heat pumps transfer heat from the outside air rather than generating heat through combustion.

In other words, an air source heat pump will make use of the air outside your property to power your central heating system.

Seasonal performance and SCOP explained

The two main ways of measuring the energy efficiency of a heat pump include COP (Coefficient of Performance) and SCOP (Seasonal Coefficient of Performance).

In short, a higher SCOP score for a heat pump denotes better energy efficiency.

SCOP Value	Efficiency Rating	Equivalent COP	Verdict
4.0	A+++	1 kWh → 4 kWh heat	Excellent efficiency
3.5	A++	1 kWh → 3.5 kWh heat	Good efficiency
3.0	A+	1 kWh → 3 kWh heat	Minimum efficiency
<2.5	Below A+	Less efficient	Underperforming

For context, a heat pump can expect to achieve a SCOP score of 3-5, whereas a boiler equivalent would score 0.9.

The greater the number, the more your energy bills will be reduced.

How they perform in cold weather

Rest assured that heat pumps are designed to heat your home all year round, including during winter.

However, the COP (Coefficient of Performance) will reduce when the outside temperatures are colder. That’s because there is less thermal heat to be extracted from the air compared with warmer months.

Most modern heat pumps are designed to work in extreme temperatures as low as -20°C. Features such as inverter technology, enhanced vapour injection and defrost cycles can all assist a heat pump as it runs during cold weath

Tips for maximising efficiency

Before getting a heat pump, you should check the energy efficiency of your property to ensure it’s adequately insulated. Newer homes often benefit from upgraded energy efficiency measures as standard, but this isn’t the case for older properties. Simply put, your heat pump will have to work harder and will cost more to run if your property isn’t well insulated.

Your heat pump installer will advise that you keep your system running all the time. That’s because air source heat pumps work best when they maintain a steady indoor temperature, rather than being switched on and off again.

You’ll also need to adjust the controls to ensure the system is running optimally, including based on the outside temperature.

Also, you will need to keep an eye on the heat pump to ensure the outdoor unit is free from debris and the indoor filter will require regular cleaning. Both of these actions are essential to maximise the efficiency of your heat pump.

Air source heat pump costs

Air source heat pumps cost between £11,000 and £16,000. However, when the Boiler Upgrade Scheme (BUS) has been applied, this reduces the cost to around £3,500 to £8,500.

It’s certainly the case that the cost of an ASHP is more expensive than a gas boiler. But, it’s also important to add some perspective. For instance, heat pumps have a typical lifespan that’s twice as long as a boiler. Heat pumps are also cheaper to run while also being better for the environment.

By getting off the gas network, you can also avoid any further worry about the rising costs of energy bills. Over the long term, this could prove to save you money.

Installation costs and what affects pricing

The supply and installation of an air source heat pump will be included in your quotation. As noted above, the typical price range for a heat pump is £11,000 to £16,000.

But, if you qualify for the boiler upgrade scheme (BUS), you can expect to pay between £3,500 and £8,500 for the cost of an ASHP with installation included.

The factors which can impact how more an air source heat pump costs include:

• Accessibility around your property
• Electrical installation
• Existing heating system
• Heat pump brand
• Heat pump size
• Home insulation levels
• Hot water cylinder
• Installer experience & accreditations
• Property location
• Property size
• Radiator and pipework compatibility
• Smart controls
• Unexpected issues
• Warranty period

Since every air source heat pump installation is bespoke, you should ask about what to expect in terms of costs and the overall work required as you collect quotes from installers.

Running costs compared to gas boilers

While a heat pump typically costs between £800 and £1,800 per year to run, this often works out considerably cheaper than gas boilers.

At the time of writing, the average UK household with a gas boiler pays between £2,067 and £2,612 per year in running costs.

Repair and maintenance costs

Air source heat pumps (ASHPs) require an annual service. Rates can vary depending on the installer, but the typical cost for heat pump servicing is between £150 to £300.

Unlike boilers, it is safe to carry out some maintenance work yourself on the heat pump including removing debris and cleaning the indoor air filters. Doing so can save you money while also helping to ensure your heat pump is running efficiently.

Heat pump warranties can vary between 2-10 years. However, if you ensure yours has good coverage, then the cost of any defects should be included.

Otherwise, air source heat pumps can cost between £500 to £2,000 to repair if any of the main components such as the compressor or fan require total replacement.

Lifespan and long-term value

Modern heat pumps have a lifespan of 20 to 25 years, which far exceeds the 10-15 year average lifespan of a traditional gas boiler.

On the whole, air source heat pumps yield faster returns, requiring 5-10 years to pay themselves off. But, if you qualify for a heat pump grant scheme such as BUS, you may recoup your investment even sooner.

Either way, by getting off gas, you’ll ultimately avoid paying future gas bills. In particular, the energy price hikes are still yet to return to pre 2021 levels, which was the year when wholesale prices first began to rise.

Our research also suggests that installing an air source heat pump can add between 1% to 10% to the value of your property. Since heat pumps are a modern way of heating and cooling your home, they can potentially be very attractive to buyers. In the coming years especially, gas and oil boilers will be phased out. So, if you’ve already done the work to convert your property to a heat pump system, this eliminates the need for the new owners to have to pay for this themselves.

Funding and financial incentives

Due to their eco-friendliness, the government has been keen to push heat pump technology by offering money to help cover the installation costs. Financial incentives are also being offered elsewhere to encourage homeowners and businesses to move to greener heating methods.

The current heat pump financial schemes you could be eligible for include:

• Boiler Upgrade Scheme (BUS)
• ECO4
• Home Energy Scotland
• Local Authority grants (ECO4 Flex)

All of the above schemes will give up to £7,500 towards the cost of the heat pump. The Home Energy Scotland grant can also be combined with an optional loan, which will provide up to £15,000 of financial support.

Businesses with commercial premises may also want to look into the 0% VAT relief scheme for heat pumps which is set to run until 2027.

What to expect during installation

Getting a heat pump installed is a major but manageable undertaking.

A heat pump for house installation requires a small team of people, including a lead installer, support installers and an electrician.

This collaborative effort ensures your heat pump installation will not only be subject to lots of expert input, but that there will be plenty of people on hand to keep you in the loop about the status of the job.

Assessment and planning

Before the practical work begins to remove your boiler and install an air source heat pump, a pre-installation assessment will be carried out. In essence, this involves performing a heat loss calculation and site inspection. The results will then allow for a bespoke design of your ASHP based on the most appropriate unit site, flow temperatures and controls.

Installation timeline and disruption

Most air source heat pumps take 2-5 days to install. In some cases, your radiators may need changing and a hot water cylinder will need to be installed if your property doesn’t already have one.

As you might expect, the more work that is required to make your system configured for a heat pump, the longer the job will take.

Since your old boiler will be removed to install a heat pump, your central heating system will need to be turned off. However, your installer should prioritise making the hot water cylinder functional so that you aren’t without hot water. Likewise, space heaters should be provided if required.

Regulations and permissions

In the vast majority of cases, air source heat pumps (ASHPs) do not require planning permission. That’s so long as they comply with the permitted development criteria.

In England, a heat pump must be installed according to MCS planning standards. This requires that the heat pump be located more than 1 metre from the property boundary. It cannot be installed on a pitched roof and should also not be near the edge of a flat roof.

In Scotland, only one heat pump is permitted on one piece of land. It must be installed at least 100 metres away from another dwelling. If the property is located in a conservation area, the heat pump cannot be visible from the road.

However, in Wales, all heat pump installations require planning permission.

Finally, you will need to inform your local district network operator (DNO) that you are installing a heat pump. Usually, your installer will handle this on your behalf so do check with them before going ahead.

Living with an air source heat pump

It can take a bit of getting used to an air source heat pump (ASHP). But once you understand how it works, an ASHP can prove to be a very efficient and cost-effective method of heating your home.

Daily use and smart controls

Air source heat pumps can be controlled using smart thermostats. Compared to the controls on a boiler, heat pump smart controls have more settings to navigate. However, they provide advanced features to ensure thermal comfort throughout your home and can even be programmed differently for when you will be away on holiday.

One of the main things to know about air source heat pumps is that they will generate consistent background warmth rather than sudden blasts of heat. It’s best to keep the heating on low continuously rather than turning the heat pump on and off.

The smart thermostat can also be used to establish different thermal zones within your property. Internal room temperatures can then be adjusted accordingly depending on the room type.

It’s also good to know that heat pumps require hot water to be stored in a cylinder rather than produced on demand as is the case with a combi boiler. But, it’s also possible to schedule reheats of the tank if you will be using lots of hot water.

Maintenance tips

Air source heat pumps require a certain level of maintenance throughout the year to maintain their performance and overall efficiency.

If you’ve been used to getting an annual service for your boiler, you’ll also need to arrange a similar check of your heat pump at least once a year. While you can schedule a traditional boiler service at any time, the best time to service a heat pump is before peak cooling or heating seasons throughout the year.

A heat pump will also require the following maintenance actions:

Every 1-3 months: Clean the indoor filter of the air source heat pump. Having a clean indoor filter is important to maintain airflow, efficiency and indoor air quality. Doing so can also reduce strain on the wider heat pump system and promote its lifespan.

Annually: Remove any dirt or grime from the evaporator and condenser coils.

As required: Conduct regular visual inspections. Ensure the heat pump isn’t blocked and that the condensate drain is flowing freely. Schedule a repair if the heat pump is making any unusual noises.

How to care for your system in winter

In the winter, it’s essential to check for debris such as snow, ice or leaves which may build up around the outdoor unit.

There is also such a thing as heat pump covers which can help protect your heat pump during the colder months. However, it is important that the heat pump cover is specifically designed so that the airflow is not restricted.

Common questions and misconceptions

It’s normal to have questions about new technology, especially when most of us are so used to traditional boilers instead.

Keep reading to discover air source heating explained where we tackle common questions and misconceptions.

Do they work in winter?

If you have visions of being freezing in winter due to your heat pump only working in summer, you’ll be relieved to know that heat pumps are designed to work all year round.

While the efficiency of a heat pump can reduce in cold temperatures, this doesn’t mean it doesn’t work. In fact, heat energy can still be extracted by an air source heat pump even during winter.

In extreme cold snaps, many air pumps have a backup system which can be triggered to ensure your home still experiences thermal comfort.

To help your air source heat pump perform at its best during more challenging weather conditions, insulating your home is essential. Also, it’s important to choose the right heat pump type and size for your home.

Are heat pumps noisy?

Heat pumps do make a noise, but the sound is mostly compared to that of a fridge. The typical noise levels generated by a heat pump fall between 40dB-60dB.

New technology is emerging all the time, meaning quieter heat pumps are available. Alternatively, you can also have acoustic enclosures added around your heat pump for a nominal cost.

Another consideration is where you install your heat pump, as its location can also make any potential noise less bothersome.

Can they fully replace a gas boiler?

With an air source heat pump how it works can seem unfamiliar. This is especially the case if you’ve been used to gas boilers until now.

Heat pumps are indeed designed to replace your gas boiler so that you can switch to a more eco-friendly system to power your hot water, radiators or underfloor heating.

During the installation, your old boiler will be removed. If you currently have a combi boiler, then you may need a hot water cylinder installed.

Since heat pumps are a newer technology, it can seem like a big step to have to get rid of your boiler. But as heat pumps become more commonplace, it will become easier to wrap your head around, especially as any neighbouring properties also make the switch as gas and oil boilers are phased out.

Are they suitable for flats or small homes?

Yes. Heat pumps aren’t just great for larger properties, as they can also be installed in smaller properties including bungalows or flats.

The only caveat is to ensure your property can facilitate a heat pump in terms of the space requirements. When you arrange for a quote, your engineer should visit your property to be able to confirm whether your property is suitable for a heat pump.

In the coming years, it is likely that heat pump technology will become more commonplace as the government looks to move away from the current reliance on fossil fuels to power our homes. So, you should also expect to see even more options for smaller properties and flats in the near future.

How to choose a trusted installer

One of the best ways to avoid problems with your heat pump is to ensure the installation is carried out by a highly competent professional.

As a minimum, the engineer should be part of the Microgeneration Certification Scheme (MCS). MSC accreditation is also a requirement if you receive any government funding for a new heat pump such as the Boiler Upgrade Scheme (BUS) grant.

MCS heat pump installers should also be registered with a consumer protection scheme such as RECC or HIES.

Similar to any other kind of home improvement work you are looking at having done, it’s important to take your time to research the company. Ideally, they should have a professional website with plenty of online reviews to back up the quality of their work.

When comparing quotes and offers, you may also want to ask the following questions:

• Are you MSC certified?
• Are you a member of RECC or HIES?
• How many heat pumps have you installed?
• Have you done a full heat loss calculation for my home?
• Is my home insulated enough for a heat pump?
• Do I need to upgrade my radiators to get a heat pump?
• What type and size of heat pump do you recommend and why?
• Will you handle plumbing and electrical work, or use subcontractors?
• What warranties are included (for the unit and workmanship)?
• Do you offer servicing, maintenance and emergency support?
• Will you register the installation for warranty and incentives on my behalf?

These questions might seem a lot to think about, but choosing the right installer can offer peace of mind since heat pumps are a costly investment.

Air source heatpumps FAQs

Still have questions about getting an air source heat pump system installed in your property? We’ve answered some of the top queries below.

For anything else, be sure to check out our other heat pump cost guides and blogs.