What Is a Monobloc Heat Pump?

Monobloc heat pumps are all-in-one systems that integrate key components—such as the heat exchanger, main pump, evaporator, condenser, and compression valves—into a single outdoor unit. This unit is typically installed against an external wall of your home.

Due to their size, monobloc heat pumps require sufficient outdoor space for proper installation. While they must be installed by a professional, the process is generally more straightforward than that of air conditioning systems or ground and water source heat pumps.

The outdoor unit connects directly to your home's existing heating system, delivering warmth through radiators or underfloor heating by extracting heat from the outside air.

To better understand how these systems work, you can start with our guide: What is a heat pump.

Pros and Cons of a Monobloc Heat Pump

Monobloc heat pumps come with several advantages and a few considerations. Here's a breakdown of the key pros and cons:

Pros of Monobloc Heat Pumps

- Space-saving design – Since monobloc systems are installed externally and contain all components within a single unit, they eliminate the need for internal heat exchangers or storage tanks, freeing up valuable indoor space.

- Simplified installation – With all major components housed in one unit, installation is more straightforward. Only basic pipework is needed to connect the system to your home's heating infrastructure.

- Easier maintenance – A self-contained system is typically quicker and simpler to service compared to split systems with multiple internal and external units.

- High efficiency and cost savings – By extracting heat from the air, monobloc heat pumps offer excellent energy efficiency. This can translate into lower energy consumption and reduced heating bills over time.

Cons of Monobloc Heat Pumps

While monobloc heat pumps offer many advantages, there are also some limitations to consider:

- Lower heating capacity – Compared to other types of heat pumps, monobloc systems may have a lower overall heating output. This can make them less suitable for large properties or homes with multiple rooms requiring consistent heating.

- Hot water storage is required – because monobloc heat pumps connect directly to your heating system, you won't get hot water from your taps on demand. You will need a hot water tank to store hot water heated by the heat pump to feed hot taps in your property.

- Not flexible – if your home gets larger after an extension or your heating needs change, you may need a new system. Monobloc heat pumps aren't adaptable to heating increased space.

- Outdoor space requirement – Monobloc units are typically large and must be installed on a ground-level external wall. Homes without adequate outdoor space may not be able to accommodate them.

- Noise – These systems can generate noticeable noise during operation. If installed near a ground-floor bedroom, they may cause disturbances, especially during nighttime use. (Learn more about how noisy heat pumps can be.)

- Cost – Due to the integrated technology, monobloc heat pumps can be expensive. It's important to compare options and ensure you choose a system that suits your property's size and heating needs to avoid overpaying.

- Reduced efficiency in extreme cold – In very low outdoor temperatures, the performance and efficiency of monobloc air source heat pumps can drop. Additionally, external pipework can lead to minor heat loss as energy is transferred into your home.

Do Monobloc Heat Pumps Produce Hot Water?

Monobloc heat pumps are designed to heat water for your central heating system, distributing it to radiators or underfloor heating. However, they do not provide running hot water for domestic use.

To obtain hot water, you'll need to install a separate hot water storage tank. The only part of the monobloc heat pump located inside your home is the connected hot water cylinder.

What is a Split Heat Pump?

Unlike monobloc heat pumps, split heat pumps consist of two separate units: an internal unit and an external unit, which serves as the heat exchanger and compressor.

Split systems are ideal for more complex installations or when there is no suitable space for a monobloc heat pump. They can also be quieter during operation.

Additionally, split heat pumps are a good option for homes with limited outdoor space, as the external unit is typically smaller.

Split systems are commonly referred to as HVAC systems. Learn more about split HVAC heat pump systems.

What is a Monobloc Air Source Heat Pump?

Monobloc air source heat pumps integrate all essential components into a single unit that can be installed outside your home.

Unlike traditional heating systems that rely on gas, most monobloc air source heat pumps use refrigerants, which means they do not require F-gas (fluorinated gas) qualifications for installation.

This design makes monobloc heat pumps generally more affordable and easier to install compared to air conditioning units or ventilation systems.

However, most monobloc heat pump systems still require installation by professional heating experts.

Where Can a Monobloc Heat Pump Unit Be Installed?

Monobloc air source heat pumps require external air, so the system is typically designed as a single outdoor unit that is installed outside the property.

The unit should be installed at ground level in a location that allows easy access for maintenance and servicing.

Many homeowners opt to place the heat pump outside their utility or boiler room, as this setup simplifies the connection to the heating system.

Due to the need to house all necessary components, the outdoor unit tends to be quite large.

Monobloc heat pumps are ideal for larger properties with ample outdoor space, where the system can be installed and operate effectively.

Can You Get Monobloc Ground Source Heat Pumps?

Yes, monobloc ground source and water source heat pumps are available. These systems connect to a suitable heat source, such as boreholes, aquifers, lakes, rivers, or waste heat, via a series of pipes.

Although they are considered monobloc systems, ground and water source heat pumps often function similarly to split systems. They require underground or underwater pumps to access heat from the ground or a body of water.

Additionally, an internal hot water tank is needed to store the heated water, which will then be used to supply hot water taps in your home.

Monobloc Heat Pump FAQs

Can a Monobloc Heat Pump Be Installed in Cold Climates?  

Most monobloc heat pumps can operate effectively in temperatures as low as -25°C. Many models designed for colder climates feature enhanced vapour injection (EVI) technology, which helps maintain refrigerant pressure even in low temperatures.

For extremely cold climates, a ground source monobloc heat pump may be a better choice, as ground temperatures tend to remain more stable year-round compared to air temperatures.

Additionally, proper air sealing, insulation, and correctly sizing the heat pump for your home are essential factors to consider.

How to Prepare Your Home for a Heat Pump?  

If you're replacing a traditional boiler with a heat pump, the changes needed are generally minimal. However, you may want to consider the following improvements:

- Enhance insulation: Proper insulation helps your home retain more heat, reducing the workload of your heat pump and improving energy efficiency. Many homes, especially in the UK, can benefit from better insulation.

- Upgrade radiators: Heat pumps perform best when they have a larger surface area to distribute heat. Upgrading your radiators can help your home reach a comfortable temperature more quickly. Replacing old radiators with aluminium ones can further improve heat distribution, as aluminium is an excellent conductor of heat.