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Which are the Best Air Source Heat Pumps?

Nick Geary
By: Nick Geary
Updated: 17th June 2022

Best air source heat pumps

Installing an air source heat pump in your home is a great way to reduce your carbon emissions and lower your heating costs. Making the decision to install one should not be taken lightly as heat pumps are quite different to the traditional boilers we are used to.
However, if you decide to go ahead, you need to be sure that you are choosing an efficient and reliable model. To help you make the right choice, we have compared the best air source heat pumps on the market below.

Comparing air source heat pumps

When trying to choose the best air source heat pump for your home, there are several things to consider, as well as the price.

Air to water or air to air

There are 2 types of air source heat pump: air to water and air to air.

Air to water heat pumps are designed to generate heat from the air outside and transfer this to the water in a central heating system.
Air to air heat pumps are more like air conditioning units that can heat the air. They generate heat from the air outside and transfer it to the air in a property's ventilation system. Air to air heat pumps generally require a full installation of an outdoor fan unit and a full ventilation system to distribute air around the property. This makes them very difficult and potentially more costly to install in existing properties, and is why our list of best air source heat pumps focuses solely on air to water models.
Find out more about how air source heat pumps work.

Low or high temperature

Most air source heat pump manufacturers provide their air to water pumps in both high temperature and low temperature models. Low temperature heat pumps are more suited to properties with underfloor heating or low temperature radiators, while high temperature heat pumps are more suited to traditional central heating systems, as they can provide water temperatures of around 75-80°C which is equivalent to a gas boiler. You can find out more about how these units compare in our Low vs High Temperature Air Source Heat Pumps article.

Monobloc or Split

There are 2 types of air source heat pump unit which are available from most manufacturers: monobloc and split. Monobloc heat pumps consist of a single outdoor unit whereas split heat pumps have an outdoor and indoor unit. There are different benefits and disadvantages to both of these heat pumps which we cover in detail here: Split Heat Pumps vs Monobloc Heat Pumps: Which is Best?

Output size

Air source heat pumps are available in a range of different (kw) output sizes. These output sizes are important, as the output you require will depend on the size of your property. To give you an idea of what size output you may need, we have provided some examples below:

  • 1 bed flat/apartment – 2-3kw
  • 2 bed terraced house – 4-5kw
  • 3 bed semi-detached house – 6-8kw
  • 4 bed house – 9-11kw
  • 5 bed detached house – 12-15kw

These are only estimates and can be affected by different situations and circumstances. You can find out what size heat pump would best suit your home here: What Size Air Source Heat Pump Do I Need?

Global warming potential

A big component of air source heat pumps is their refrigerants. These gases are the only part of an air source heat pump which may negatively impact the environment. This is because they all have a global warming potential (GWP). The GWP of a gas is a comparative value that indicates the greenhouse effect of a greenhouse gas, should it be released into the atmosphere. The higher a gas's GWP is the more damaging it would be for the environment (carbon dioxide has a GWP of 1). We have provided a table of the refrigerants air source heat pumps use and their GWPs below:

Refrigerant Type Global Warming Potential (GWP)
R290 3
R32 677
R410A 2,088

For an in-depth overview of what you will need to consider before buying an air source heat pump, you can go to our article: Buying an Air source heat pump – What you need to know

The best heat pumps and prices

After hours of in depth research around different air source heat pumps which are currently available (air to water), we have compiled a list of the 9 best heat pump ranges on the market.

To make them easier to compare, we have also provided key features, facts and figures, and a short description of the air source heat pumps available within each range.

1. Daikin Altherma 3

Manufacturer Range Available Outputs (kW) ErP Energy Efficiency Rating Potential Price
Daikin Altherma 3 4 – 18 A++ £7,000 - £11,000

Key features:

  • Includes high temperature and low temperature pumps.
  • Heat is still generated in outdoor temperatures as low as -25°C.
  • Includes units compatible with solar power.
  • All units in the range use the refrigerant R32.
  • Includes both split and monobloc units.
  • Indoor units with integrated hot water storage tanks are available.
  • Includes units with a low sound mode for minimal disturbance.

The Daikin Altherma 3 range includes a low temperature range (Altherma 3 R) and a high temperature range (Altherma 3 H HT). This means whether you have an old central heating system, newer radiators or underfloor heating, there will be an option that suits your needs.
The Altherma 3 R (low temperature) range includes the option of a monobloc or split air source heat pump. These units require a hot water tank to allow for hot running water as well as heating. They are also compatible with low temperature radiators and underfloor heating.
The Altherma 3 H HT (high temperature) range only includes split air source heat pumps. There are 3 choices of indoor unit with 2 units having integrated hot water tanks for hot running water, and the third requiring a separate hot water tank for hot running water. As these are high temperature air source heat pumps, all units are compatible with existing traditional central heating systems. The outdoor unit has a low sound mode making it as quiet as 35db(quieter than a library).
Find out more about the Daikin Altherma 3 range

2. Nibe F2040

Manufacturer Range Available Outputs (kW) ErP Energy Efficiency Rating Potential Price
Nibe F2040 6 – 16 A+++ £3,500 - £8,500

Key features:

  • Works down to outdoor temperature of -20°C.
  • Works with smart technology and has integrated wifi, when combined with an indoor module.
  • Has a silent operation function to reduce noise when needed.
  • Only includes low temperature heat pumps.
  • No option for a split unit.

The Nibe F2040 air source heat pump range is one of the more straightforward options available. Each F2040 consists of a monobloc outdoor fan unit which can be controlled with integrated smart technology. A separate hot water tank will be required, to allow for hot running water.
Find out more about the Nibe F2040 range

3. Samsung Eco Heating System

Manufacturer Range Available Outputs (kW) ErP Energy Efficiency Rating Potential Price
Samsung Eco Heating System 4 – 16 A+++ £2,200 - £9,000

Key features:

  • 3 unit types available: mono, split and TDM plus.
  • TDM plus design is exclusive to Samsung.
  • Only includes low temperature heat pumps.
  • Some units use the R32 refrigerant.
  • Will work in temperatures as low as -25°C.
  • Solar compatible.
  • Indoor units with integrated hot water tanks available.
  • Includes units with a quiet mode to reduce outdoor noise.

Samsung is a company that's always trying to be at the forefront of technology. This is no different, when it comes to air source heat pumps. The Samsung Eco Heating System has an option for outdoor units that is not available from any other heat pump company, in the TDM plus. This can be used to heat the water in a property for hot running water and heat the air in a ducting system to heat the property. This is something you would usually need 2 separate outdoor units for.
If you don't have an existing hot water storage tank in your house, you can opt for a ClimateHub indoor hydro unit with an integrated hot water tank. The ClimateHub is compatible with all of the available outdoor unit types in the Samsung range.
Find out more about the Samsung Eco Heating System range

4. Vaillant aroTHERM

Manufacturer Range Available Outputs (kW) ErP Energy Efficiency Rating Potential Price
Vaillant aroTHERM 3.5 – 12 A++ £3,000 - £8,500

Key features:

  • Range includes high temperature and low temperature units.
  • Both mono and split units are available.
  • Some units use the R290 refrigerant with a very low global warming potential (GWP) of 3.
  • Indoor units with integrated hot water storage tanks are available.

Vaillant’s aroTHERM air source heat pump range has 2 main types of outdoor unit: The aroTHERM plus and the aroTHERM split.
The aroTHERM plus is a high temperature air source heat pump which means it can be connected to an existing wet central heating system. It can also be used in conjunction with a Vaillant uniTOWER control unit which has an integrated hot water storage tank to avoid the need of installing a separate hot water storage tank, for hot running water, somewhere in the property.
The aroTHERM split is a low to medium temperature air source heat pump which is more suitable for low temperature radiators and underfloor heating. It also requires the installation of a separate hot water storage cylinder, to allow for hot running water in the property.
Find out more about the Vaillant aroTHERM range

5. Viessmann Vitocal

Manufacturer Range Available Outputs (kW) ErP Energy Efficiency Rating Potential Price
Viessmann Vitocal 2.3 – 16 A+++ £5,000 - £8,500

Key features:

  • All units in the range have advanced acoustic design for quiet running.
  • Some units use the R32 refrigerant which is more environmentally friendly than R410A.
  • Only includes medium and low temperature heat pumps.
  • Indoor units with built in hot water storage tanks are available.

The Viessmann Vitocal range contains some of the most compact outdoor units on the market and has 3 main models available: Vitocal 100-A, Vitocal 200-A and Vitocal 222-A.
The Vitocal 100-A is the most compact monobloc unit available in the range. It uses a more environmentally friendly refrigerant in its heating process, and requires the installation of a separate hot water tank for running hot water.
The 200-A can achieve a maximum flow temperature for hot water of 60°C, even in outdoor temperatures of -10°C. It can be combined with an existing central heating system, as an additional heat source, alongside a boiler, to cover the majority of demand and improve the efficiency of the central heating system dramatically.
The Vitocal 222-A can be combined with an indoor unit that has an integrated 220L hot water storage tank. This removes the need for a separate hot water cylinder for hot running water.
Find out more about the Viessmann Vitocal range

6. Grant Aerona³ R32

Manufacturer Range Available Outputs (kW) ErP Energy Efficiency Rating Potential Price
Grant Aerona³ R32 6 – 17 A++ £3,000 - £9,000

Key features:

  • Entire range uses the R32 refrigerant.
  • Some units have been awarded the Quiet Mark for the low noise levels they produce.
  • Range only includes low temperature heat pumps.

The Grant Aerona³ R32 range takes its name from the refrigerant the air source heat pumps use. This is because the refrigerant R32 is more environmentally friendly than R410A and is utilised across the entire range.
These heat pumps are more suited to homes that use underfloor heating or low temperature radiators, and also require the installation of a separate hot water cylinder, if you want to use them for hot running water.
Find out more about the Grant Aerona³ R32 range

7. Mitsubishi Ecodan

Manufacturer Range Available Outputs (kW) ErP Energy Efficiency Rating Potential Price
Mitsubishi Ecodan 4.5 – 14 A++ £4,000 - £6,000

Key features:

  • Range includes units which use the R32 refrigerant.
  • Ultra quiet models are available.
  • Includes special units for use on coastal properties.
  • Some units will produce heat at outdoor temperatures as low as -20°C.
  • Range only includes low temperature heat pumps.

The Ecodan range from Mitsubishi includes a selection of different air source heat pumps which are tailored to specific preferences and needs.
The Ecodan R744 QUHZ-W40VA is the most compact outdoor unit in the range, and it utilises one of the most environmentally friendly refrigerants available on the market. If you live by the coast, there are a selection of 'Coastal Protection' units which are less likely to degrade due to salt water damage, and there is also a selection of units which have been designed to be as quiet as possible.
Find out more about the Mitsubishi Ecodan range

8. LG THERMA V

Manufacturer Range Available Outputs (kW) ErP Energy Efficiency Rating Potential Price
LG THERMA V 5 – 16 A++ £2,000 - £6,000

Key features:

  • Range includes high temperature pumps, capable of heating water to 80°C.
  • Some units will still produce heat in outdoor temperatures as low as -25°C.
  • Both split and monobloc units are available.
  • Includes units which use the R32 refrigerant.
  • All units require a separate domestic hot water tank for hot running water.

The THERMA V range includes units that can operate in temperatures as low as -25°C and heat water to a maximum of 65°C. Their hot temperature heat pumps can heat water to 80°C and include a selection of models with both split and monobloc options.
All of the units in the THERMA V range are compatible with smart heating control and can be controlled from anywhere with the use of the LG SmartThinq app.
Find out more about the LG THERMA V range

9. Hitachi Yutaki

Manufacturer Range Available Outputs (kW) ErP Energy Efficiency Rating Potential Price
Hitachi Yutaki 4.3 – 24 A+++ £3,000 - £8,000

Key features:

  • Range includes units capable of producing hot water of temperatures up to 80°C.
  • All units operate at temperatures as low as -15°C with some operating at -25°C.
  • Indoor units with integrated hot water tanks are available.
  • All outdoor units have an exclusive smart defrost cycle which improves energy efficiency.

Hitachi’s latest Yutaki heat pump range has been designed to be as energy efficient as possible. Each heat pump is also designed to be easy to install and maintain.
The range includes the Yutaki S80 which can heat water to temperatures of 80°C, even if the outside temperature is as low as – -25°C. There is also the Yutaki S Combi which has an integrated water tank for hot running water.
Find out more about the Hitachi Yutaki range

Which is the best air source heat pump for you?

Whichever air source heat pump you choose to install will be highly efficient, helping to reduce your energy bills. However, choosing an overall winner from the air source heat pumps we've listed is tough. When deciding on which heat pump would be best for you, there are some things about your circumstances you should consider.

If you live in a particularly cold area

Your biggest concern will be if the appliance can still operate when the temperature drops during winter. The majority of the air source heat pumps will still run at low temperatures, but only the Daikin, Samsung, LG and Hitachi models will run in temperatures as low as -25°C.

If cost is a priority

If you want to move towards greener energy, but don't want to break the bank, you probably won't want to spend too much on an air source heat pump. The most affordable models on our list are the LG Therma and the Samsung eco heating system, with the lowest priced units costing £2,000 and £2,200 respectively. Around £1,000 cheaper than the other air source heat pumps on our list.

If the environment is a priority for you

One of the big reasons to replace your gas boiler with an air source heat pump is to make your home more energy efficient and environmentally friendly. If this is your sole focus, you'll want to get one of the heat pumps with the lowest global warming potential (GWP). As the Vaillant range includes units which use the naturally occurring R290 refrigerant (which has a global warming potential of 3, the lowest possible GWP is 1), it is definitely the best choice for anyone who is committed to lowering their impact on the planet.

For larger and older properties

The Hitachi heat pump is the best choice for larger homes, as it can heat water to 80°C to handle a higher demand for hot water for more radiators and bathrooms. It also requires no change to the radiators in an older property, as 80°C is a perfectly fine water temperature for existing radiators and pipework.

Make an informed choice

Whilst we've outlined some of the best air source heat pumps available, we can't predict which unit will be best suited to your home, based on your unique needs. That's why we would recommend getting in touch with a local professional heat pump engineer for some tailored advice.

Fortunately, this is something we can help with. Follow the link below and we'll find heat pump engineers in your area for you, in no time.



Nick Geary

About the author

Nick Geary

Nick has a wide range of experience writing about conventional and renewable heating solutions, and is always increasing his knowledge by researching any new heating technologies on the horizon.

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