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Monobloc vs Split Air Source Heat Pumps: Which is Best?

Becky Mckay
By: Becky Mckay
Updated: 21st March 2022

monobloc or split air source heat pump
If you're thinking of getting a new air source heat pump, one of the things you will need to consider is what type of heat pump suits your property best, a monobloc or a split unit?

What is a monobloc air source heat pump?

A monobloc air source heat pump comes in one single outdoor unit. This connects directly to the heating system of a property and can be controlled by an indoor control panel or thermostat. There is often also an outdoor control panel for the unit too.

Benefits of a monobloc heat pump

There are several benefits to choosing a monobloc air source heat pump-which we have detailed below.

More indoor space

As monobloc air source heat pumps are a single outdoor unit, they are very effective at providing more space inside your property. Depending on what kind of boiler you had installed previously, you could gain some indoor space from where the boiler used to be.

Easier to install

Monobloc units are self-contained, meaning there is no need for the connection of refrigerant pipes. This means any trained heating engineer should be able to install one with little difficulty, as the only connections that need to be made are those of water pipes to the central heating system. Due to the simplicity of their installation, monobloc air source heat pumps can be installed quickly which, in turn, makes their installation less costly.

Easy to maintain

Due to their all-in-one design, monobloc heat pumps are easy to maintain. While this is more of a benefit to heating engineers that will be doing the maintenance, it could also mean that having someone at your property to run maintenance on your heat pump will take less time out of your day.

Disadvantages of a monobloc heat pump

When choosing the best heat pump for your property, it is important to consider the disadvantages of each unit too. You can find the disadvantages of installing a monobloc heat pump below.

No hot water

Whilst you can have a monobloc air source heat pump connected directly to your central heating system, to heat the water in your radiators or underfloor heating, you will not get any hot running water without the installation of a separate hot water storage tank. If you already have a regular boiler or system boiler installed at your property, this will only mean replacing the existing hot water tank. However, if you have a combi boiler, a new hot water storage tank will likely take up space in your property that was previously free.

Lack of flexibility

Monobloc air source heat pumps have to be connected directly to the central heating system in a property. This means they will need to be located on an outer wall of your property with very little flexibility of whereabouts they can be installed.

Less outdoor space

A big drawback of monobloc air source heat pumps is their size. Due to them being an all-in-one unit, there is a lot of technology to fit in a single box. This makes them very large. If you have a small garden or your home has little or no front garden, you are going to struggle to find enough space to install a monobloc unit. Even if you do have enough space at the back of your property, the unit still needs a reasonably clear area around it to allow it to work at peak efficiency.

More noise

Due to monobloc units being bigger than split units, it also makes them noisier. We have provided comparative noise levels for a selection of air source heat pumps in our 'How Loud Are Air Source Heat Pumps?' article.

What is a split air source heat pump?

Split air source heat pumps consist of an outdoor fan unit and an indoor hydro unit. While the outdoor fan unit extracts ambient air from outside the property, the indoor unit heats the refrigerant and transfers its heat to the water in the central heating system. It also acts as a thermostat and control panel.

Benefits of a split air source heat pump

When choosing a split air source heat pump over a monobloc heat pump, there are several benefits which we have detailed below.

More outdoor space

The outdoor units of split air source heat pumps are considerably smaller than their monobloc counterparts, and will take up far less space outside of your property. Due to their smaller size they are generally quieter to run as well.

Hot running water

Depending on the split air source heat pump you choose, you may not need a separate hot water storage tank to allow for hot running water in your home. This is because there are several indoor unit options that include an integrated hot water storage tank in their design. These units can completely negate the need for a separate hot water storage tank, or reduce the size of separate hot water storage tank you will need, depending on the unit you choose.

Flexible installation

As the indoor unit of a split heat pump is the only part that's connected to the central heating system, this gives you more freedom with where you can place the outdoor unit. Some split air source heat pumps allow for the outdoor unit to be placed up to 75m away from the indoor unit. This gives you the potential to place the outdoor unit at the bottom of the garden out of the way, or up on a wall that is less intrusive.

Disadvantages of a split heat pump

When choosing the best heat pump for your property, it is important to consider the disadvantages of each unit too. You can find the disadvantages of installing a split heat pump below.

Complicated installation

Due to the separate indoor and outdoor units, split heat pumps are more complicated to install. Many of them require the installation of refrigerant connections (which can only be done by a heating engineer with F gas qualifications). This makes the installation more time consuming and is likely to increase the cost. As these units are also relatively new, you may find it harder to find a qualified heating engineer in your area as well.

However, this is something we can help with. Click the link below and we'll get you quotes from up to 3 qualified heating engineers in your area.



Less indoor space

Unsurprisingly, installing a split air source heat pump will probably take up more room inside your property than a monobloc heat pump. Mainly due to their being an indoor unit as well as an outdoor unit. The most drastic loss of indoor space you could face with a split heat pump is installing an indoor unit and separate hot water storage tank. This would not only fill the space your boiler previously inhabited, but take up further space with a hot water storage tank. This can be remedied by opting for an indoor unit with an integrated hot water storage tank, but it is not something that should be overlooked.

More expensive

Being more complicated in design than a monobloc heat pump, split air source heat pumps are generally a little more expensive to buy. Couple this with a potentially more costly installation and the difference in price can start to add up. However, there is no guarantee a split heat pump will cost more than a monobloc, and you should always get comparison quotes to ensure you get the best installation price possible.

Picking the best air source heat pump

Unfortunately, when it comes to picking the best air source heat pump, there is not a definitive answer. All you can do is use the information we have provided and compare it against your circumstances. The best air source heat pump for you will be whichever best suits your home and your needs.

Whenever making a decision as big as this, we highly recommend getting advice from a local heating expert. Luckily, this is something we can help with. Click the link below and we'll provide you with free no-obligation quotes from qualified heating engineers in your area. You can then pick the best quote and get the best heating solution for your home.



Becky Mckay

About the author

Becky Mckay

Becky is one of our home heating and renewable energy experts and has a wealth of experience writing about the world of heating.

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