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The ultimate guide to air source heat pumps

Understanding air source heat pumps for your home

When upgrading any aspect of your home heating, it can only be a good thing to gain a full and thorough understanding of every single option available. And whilst you probably know about the basic merits of radiators and heated towel rails, air source heat pumps are one vice that probably aren’t so universally recognised or appreciated.

We’re looking to change that, so we’ve put together a guide covering how air source heat pumps work, what are the upfront costs of an air source heat pump as well as running bills, and how they can impact on the overall operations of your home heating.

Can they work alongside radiators? Act alone as an energy efficient heat source indoors or outdoors? Or be teamed with your existing central heating system to deliver sufficient hot water and a generally impressive heat output?

What are the pros and cons of air source heat pumps?

We’ll answer all these questions and more in this, our Ultimate Guide to Air Source Heat Pumps.

What is an air source heat pump?

Pair of grey air source heat pumps

Generally, the vast majority of home heating systems generate heat via the burning of fuel, or conversion of electricity. Air source heat pumps differentiate greatly, as they don’t actually generate heat.

Instead, an air source heat pump will transfer heat from the outdoors to inside a building or the other way around.

It does so by making use of a refrigerant system that features a condenser and compressor to absorb heat in one area and release it in another space.

For domestic properties, an air source heat pump will soak up heat from the air outside and release it within the home via hot water-filled radiators, underfloor heating, hot air or as a hot water supply.

Essentially, air source heat pumps can operate in the same manner that a traditional gas boiler does. They can keep your home nice and cool in the summer, toasty warm in the colder winter months, and provide hot water up to optimal temperatures of 80°C.

Furthermore, they perform in an economically friendly manner, as they don’t feed off fossil fuels and thus don’t give off any carbon emissions.

So, how do air source heat pumps operate?

How do air source heat pumps work?

A good way to think about the way air source heat pumps actually work, is to imagine them performing in the opposite way to a fridge, thus heating your home as opposed to cooling it.

The air from outside travels over a conglomeration of tubes containing refrigerant fluid. This heats the refrigerant up, transforming it from a liquid into a gas.

At this point, the gas journeys through a compressor to enhance the pressure and ramp up the heat. The compression process harbours similarities to topping up the air pressure in car tyres, with the air hose heating up simultaneously.

From there, the warm, compressed gases make their way into a heat exchanger, shrouded by water or cool air. The refrigerant will then shift its heat to the cool air or water, all the while warming it up. This energy is then distributed around the indoor space to deliver a heat output.

Whilst your home is warming up, condensation leads the refrigerant to return to a cool liquidated state before the cycle begins again.

What types of air source heat pumps are there?

There are two main types of air source heat pumps, broadly defined as air-to-heat and air-to-water models.

We’ve already touched on how the air-to-heat air source heat pumps operate – largely like a refrigerator does in reverse.

In the case of air-to-water heat pumps, the process is slightly different. Heat is gathered from the outside air before being fed into your wet central heating system.

Considering that the heat distributed is cooler than that typically provided by a conventional boiler, you might find it is necessary to fit underfloor heating, bigger radiators, or more designer radiators to make up the heat output deficit.

One of the most attractive aspects of air-to-water heat pumps for potential buyers though, is that they qualify under the government-led Renewable Heat Incentive (RHI). This could offset the cost of purchasing multiple supporting heating components, for instance.

This scheme essentially contributes cash towards the running costs of renewable heating in homes.

As such, air-to-water heat pumps are particularly popular options for new-build properties. They can also prevent large-scale potential disruption to your home’s aesthetic and massive future outlays by including the air source heat pump within the initial building specifications.

The retrofitting of underfloor heating can be an extremely timely, invasive and expensive practice, for instance, as explained in our Ultimate Guide to Underfloor Heating.

Meanwhile, there is one more type of air source heat pump to touch on, despite its design and way of working rendering it far less conducive to efficient home heating efforts than its counterparts.

Air-to-air heat pumps simply take heat from the outside air and use fans to spread it throughout your home. The big drawback with these systems, and a deal breaker for most, is their inability to produce hot water.

Do air source heat pumps need electricity to run?

Grey air source heat pump nearby white back door and window

All types of air source heat pumps need electricity to run. However, the way they operate ensures they will generate more heat than the amount of electrical energy they consume, effectively making them far more energy efficient than traditional electric home heating means.

Just how much more efficiently they perform will relate specifically to which make and model you opt for, and you can gain a deeper insight in our blog on The Ins And Outs Of Modern Electric Heating.

To measure the efficiency of an air source heat pump, or put more simply, how much heat energy it delivers per kW of electricity, the pump itself will usually be referred to as a SCOP, which is an acronym for Seasonal Coefficient of Performance.

Typically, this will be displayed as a simple number that refers to the level of heat energy produced in kilowatts per every 1kW of electricity utilised.

As an example, should an air source heat pump boast a SCOP of 3.2, it indicates that 3.2kW of heat will be emitted per every 1 kW of electricity it saps.

What is the difference between air source heat pumps and ground source heat pumps?

There are several standout differences between air source heat pumps and ground source heat pumps, and the main one sticks out like the thumb you clobbered with a hammer whilst putting together one of our radiator covers.

That is, of course, the way they source their heat. As each moniker would suggest, air source heat pumps take heat from the air, whilst ground source versions will make like Paul Weller, and go underground to consume inherent heat.

Ground source heat pumps would tend to deliver a slightly more efficient performance than their air source counterparts as well. Making use of the SCOP measurement method aforementioned, air source heat pumps will usually garner a SCOP rating in the 3.4 region, whilst ground source heat pumps will generally be in the 4.2 range.

With regards to installation, it’s more of a rigmarole to fit ground source heat pumps, with significant invasive groundwork required to provide a suitable foundation. Either a large surface area will need to be dug up, or a deep borehole created to store the system pipes underground. Unless you’re qualified to carry out this sort of work yourself, you’ll experience much higher initial installation costs for ground source heat pumps, as no such efforts are involved in fitting air source options.

However, the Renewable Heat Incentive Scheme does offer bigger rewards for ground source models, so you can expect to see a better return on your investment for selecting that type. Whilst the figures are subject to change and it can be a volatile barometer, the use of ground source heat pumps would allow the owner to claim 21.16p per kW of energy used, according to the latest published statistics from the Ground Source Heat Pump Association. By contrast, air source heat pumps fetch RHI payments of 10.85p per kW at this time, but as stated, these values are prone to fluctuation. Our UK Heat Pump Grants blog features a more detailed account of government incentives as it pertains to various heat pumps, while this also more information in this air source heat pump guide from the Energy Saving Trust.

How much do air source heat pumps cost?

Heating engineer with white gloves tending to air source heat pump

Sensibly, pricing will be at the very forefront of concerns for most would-be buyers of air source heat pumps. And rightly so, considering they represent a very significant investment.

Generally, a good quality air source heat pump will cost somewhere in the vicinity of £7,000. But when factoring in installation costs too, you probably won’t be getting much change out of £10,500.

But don’t forget to consider the RHI payments you’d be eligible for once the system is up and running, and also think to compare the cost of this type of heating system with other renewable energy vices.

Plus, the fact that from April 2022, the government plans to provide homeowners in the UK and Wales with £5,000 subsidies to swap gas boilers for air source heat pumps (more on this later).

A working, fully installed ground source heat pump can cost between £14,000 and £20,000, whilst biomass boilers tend to start at £15k and have a similar price ceiling to ground source heat pumps. And whilst the most commonplace of heating systems in gas combi boilers are also comfortably the cheapest to buy at between £1,500 and £3,500, they’ll cost more to run year after year and time after time.

If you’re lost, you can look and you will find that once fitted, air source heat pumps are likely to cost around £750 per year to run, which is comfortably cheaper than a standard gas combi boiler would (£900 – £1,000).

Add in the money you would receive under the government’s Renewable Heating Incentive scheme, and the impact an air source heat pump can have on your heating bills over time becomes more appealing still.

Government grants for air source heat pumps

In addition to the Renewable Heat Incentive payments already discussed, new plans unveiled in October 2021 suggest that new government grants will be available to incentivise the installation of air source heat pumps for homeowners.

Property owners in England and Wales will be entitled to receive £7,500 subsidies from April 2022 and beyond to help them replace old gas boilers with low-carbon heat pumps.

The move will form an integral part of a £3.9bn government plot to reduce carbon emissions in the heating of homes and commercial buildings.

Basically, it will act as a leg up for homeowners to swap their gas boilers for air source heat pumps, in the hope that no new boilers will be sold after 2035.

The overall aim is to make homes and business properties more energy efficient, and whilst the proposition has drawn initial criticism for lacking ambition, it is certainly welcome news for those already considering a switch to an air source heat pump.

Even if, as experts suggest, the proposal will struggle in its aim of drawing 600,000 air source heat pump installations across the UK by 2028, it is certain to attract more homes and businesses to considering swapping gas boilers for low-carbon heat pumps.

The advantages and disadvantages of air source heat pumps

At this point of the article, you’ve probably ascertained for yourself what some of the main plus points and drawbacks are concerning the purchase and installation of air source heat pumps.

Even so, we’ve not covered everything just yet, and it’s always handy to have all the most important pros and cons compiled into a neat and tidy shortlist.

Below are the main benefits and drawbacks of air source heat pumps.


  • Easy installation – In comparison with other economically friendly heating solutions, air source heat pumps incorporate by far the easiest installation process. As a result, they are cheaper to fit than other green heating options as well.
  • Economically friendly – An air source heat pump operates in a far more economically friendly manner than a traditional gas boiler. As such, your home heating will emit far less CO2 to the earth’s atmosphere.
  • Renewable Heating Incentive eligibility – You’ll qualify to receive RHI payments under the government-led scheme if you choose to fit an air source heat pump. Therefore, you can be confident of garnering a significant return on your investment over time.
  • Cheaper to run – In addition to enabling you to earn some kickback from the Renewable Heating Incentive program, air source heat pumps will also prove cheaper to run than a traditional gas boiler would. So you can enjoy lower energy bills as well as regular RHI sweeteners.


  • Initial cost – The typical main concern for would-be investors in air source heat pumps is understandably the initial cost. Although they are cheaper to buy and install than alternative renewable heating solutions, air source heat pumps still cost a pretty penny to secure and set up. Considerably more so than the more popular conventional gas boilers do.
  • Heat output – Generally speaking, air source heat pumps do not always provide as high a heat output as you might require to sufficiently heat a home. You may require additional or larger radiators to deliver an adequate level of warmth, whilst some air source heating systems explicitly state that they will perform better alongside an underfloor heating system. (There’s no fancy talking version, but their manual will indicate as much.)
  • Noise – Significant noise can emanate from air source pump condensers, which will also emit cold air. The persistent sound could be irritating if you are nearby to the unit situated on the outside.
  • Electric operation – Air source heat pumps require electricity to operate successfully, so they can’t be described as an absolutely zero-carbon venture. That is, of course, unless you generate electricity for your home via another renewable energy source such as a wind turbine or solar panels.

Is there a cheaper air source heat pump alternative?

Large light grey air source heat pump with plant sat on top of it

Given that so many see the initial purchase price as a major deterrent to fitting an air source heat pump, plenty of people will be interested in seeking a cheaper renewable heating alternative.

Of course, over the course of its lifespan, an air source heating system will in essence pay for itself and work out a lot less expensive to run than a traditional gas boiler. But if you aren’t in a position to invest so heavily up front, an air source heat pump investment will unfortunately be a non-starter.

So, are there any reasonably priced alternatives that work in a similar way?

Sorry to be the bearer of bad news, but in all honesty, air source heat pumps represent the cheapest and most economically friendly domestic heating option available.

If they are beyond your budget from an initial outlay perspective, the likeliest next best proposition is a contemporary, energy-efficient gas boiler.

These won’t come spectacularly cheap either, but at a much more generally affordable cost (£1,500 – £3,500) than an air source heat pump would. And they’ll be worth the extra cash as well – the modern models will perform far more energy efficiently than an old gas boiler would, leading to reduced heating bills over many years moving forwards.

Frequently Asked Questions

Air source heat pumps are only about as noisy as a standard household fridge. And considering they will be installed outside the home, the low level of noise they produce whilst in operation shouldn’t be of any concern at all.

In actual fact, air source heat pumps are actually quieter than other household appliances such as washing machines, and actually emit a slightly lower sound output than traditional gas boilers as well.

For further information, take a look at our blogs, Busting The Myths About Air Source Heat Pumps, and our Ultimate Guide To Air Source Heat Pumps, and this air source heat pump guide from the Energy Saving Trust.

The size of air source heat pumps varies from as little as 0.22m3, with the biggest design accounting for 0.43m3 of space.

For context, a standard size wheelie bin is only very slightly larger than the heftiest air source heating system, taking up 0.44m3. So all in all, there shouldn’t be too much concern over how much room an air source heat pump will cover.

To find out more, take a look at our dedicated blogs – Busting The Myths About Air Source Heat Pumps, and our Ultimate Guide To Air Source Heat Pumps, or consult air source heat pump guidance from the Energy Saving Trust.

It is possible to use an air source heat pump with underfloor heating, and in fact it represents one of the very best heating solutions with which to combine an air source heating system overall.

Air source heat pumps work in a far more efficient manner at a lower temperature than gas boilers. And as such, the teaming of an air source heat pump with underfloor heating is a superb one, as it is alongside larger radiators. Both these heating options provide heat at a lower temperature over a longer period of time.

For a more detailed insight into RHI air source heat pumps on the whole, take a look at our dedicated blogs surrounding the subject. Heat Pump Grants – Your Key Questions Answered, and The Ultimate Guide To Air Source Heat Pumps are both live in the BestHeating Advice Centre, whilst there’s also air source heat pump guidance available from the Energy Saving Trust.

From April 2022 onwards, homeowners in the UK and Wales can claim a £5,000 government grant to help with the cost of air source heat pumps.

As initial air source heat pump installations will typically cost in the region of £10,000 to £10,500, this offsets a significant portion of air source heating costs to begin with.

Our blog, Heat Pump Grants – Your Questions Answered has details on everything you need to know about air source heat pump government grants. Or, you could visit our Ultimate Guide To Air Source Heat Pumps for further insight, or consult air source heat pump advice from the Energy Saving Trust.

Air source heat pumps can generally act as the main heat source for a property, although in some instances additional support may be required in the form of accompanying radiators or underfloor heating.

Depending on the size and layout of the home or commercial building, it could be that radiators for air source heat pumps are required to ensure the space is properly heated.

To find out more about using air source heat pump radiators, air source heat pump underfloor heating, and all else surrounding air source heating systems, be sure to explore our comprehensive blogs on the subject.

Heat Pumps – Your Questions Answered, and The Ultimate Guide To Air Source Heat Pumps are both live in the BestHeating Advice Centre. Alternatively, you can seek further air source heat pump advice from the Energy Saving Trust.

From October 2023 onwards, homeowners in the UK and Wales will be eligible to receive a £7,500 subsidy when installing an air source heat pump on their property.

This legislation is set to replace the Renewable Heat Incentive (RHI) scheme currently in place, ensuring that those with air source heating systems are eligible to receive financial assistance for their low-carbon heating solutions from the off.

Our blog, Heat Pump Grants – Your Questions Answered offers a more detailed insight into which grants for air source heat pumps are available. You can also find further information in our Ultimate Guide To Air Source Heat Pumps, or seek air source heat pump advice from the Energy Saving Trust.

Get in touch with BestHeating

Hopefully, by now you’ll have a solid understanding of how air source heat pumps work, and the lasting impact they can have on your home heating bills and operations, as well as their positive environmental impact.

If you would like to know more about air source heat pumps, or any other renewable home heating options, please don’t hesitate to get in touch with us. You can leave your thoughts in the comments section below, or contact us via InstagramFacebook or Twitter.

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