Choosing between a monobloc or bibloc air source heat pump is a common question when looking to install an efficient heating, cooling and domestic hot water system. Both options work with a heat pump and make use of energy from the outside air, but they are not installed in the same way and do not suit every property equally. The choice depends on several factors: available space, local climate, type of property, distance between the outdoor unit and the indoor system, risk of frost, budget, and heating or hot water requirements.
Simply put, a monobloc air source heat pump houses most of the system in a single outdoor unit. From there, hot or cold water is sent into the property. A bibloc air source heat pump, also known as a split system, is divided into an outdoor unit and an indoor unit, usually connected by refrigerant lines. That is why, when comparing bibloc and monobloc air source heat pumps, you need to choose the one that best suits each installation.
Advantages of monobloc air source heat pumps
Monobloc air source heat pumps stand out for their simple installation and for requiring less space inside the property. They are a very interesting solution for renovations, homes without a plant room, or installations where the aim is to minimise indoor work.
Simpler installation
In a monobloc system, the refrigeration circuit is integrated inside the outdoor unit. In most cases, this avoids the need to connect refrigerant pipes between the outside and the inside. Installation mainly focuses on hydraulic and electrical connections, which can simplify the work and reduce installation time. Even so, it remains essential for the system to be correctly sized and installed by professionals.
Less indoor space required
Since the main unit is located outside, a monobloc air source heat pump takes up less space inside the property. It may require a domestic hot water cylinder, expansion vessel or other auxiliary components, but it does not require a dedicated indoor unit, making it a good option for flats, small terraced houses or homes without a large technical room.
A good option for renovations
Monobloc systems are often an excellent fit for renovation projects because they minimise the amount of work required inside the home. If the aim is to replace an old boiler with a more efficient system without overly complicating the installation, it can be a very practical alternative.
It also makes integration easier in homes where extensive modifications to the internal layout are not desired.
Suitable for mild or moderate climates
Monobloc air source heat pumps work particularly well in areas with mild or moderate winters. In these conditions, they can offer very efficient performance, especially if the property is well insulated and equipped with underfloor heating, fan coils or low temperature radiators.
They can also be installed in colder regions, but outdoor pipework must be properly protected against possible frost.
Advantages of bibloc air source heat pumps
Bibloc air source heat pumps split the system into an outdoor unit and an indoor unit. This configuration can be more complex, but it also offers greater flexibility in certain installations. It is often an attractive option for large homes, new builds, cold climates or projects where a dedicated plant room is available.
Greater installation flexibility
Bibloc air source heat pumps make it possible to adapt the installation more effectively to properties with more complex layouts. By separating the outdoor and indoor units, it may be easier to deal with distances, pipe runs or specific installation locations.
This is particularly useful in detached houses and larger homes where the outdoor unit cannot be positioned close to the indoor hydraulic system.
Better protection against frost
One of the main advantages of a bibloc air source heat pump is that the hydraulic circuit generally remains inside the property. Refrigerant, rather than water, circulates between the outdoor and indoor units. This reduces the risk of outdoor pipe freezing, which is especially important in areas with sub zero temperatures or harsh winters.
A good option for large homes
Bibloc air source heat pumps generally adapt well to homes with higher energy demand, multiple heating and cooling circuits, large domestic hot water cylinders or more technical installations. This does not necessarily mean they are always more powerful than monobloc systems, but they offer greater design flexibility in complex systems.
Organised integration in a plant room
If the property has a garage, large storage area or plant room, a bibloc system allows the indoor unit, hot water cylinder, pumps, accumulators and other hydraulic components to be organised more efficiently. In new build projects, this option can be particularly convenient because everything can be planned from the outset.
All the differences between bibloc and monobloc air source heat pumps
The difference between bibloc and monobloc air source heat pumps is not limited to the number of units. It also affects the installation, required space, maintenance, cost and protection against cold weather.
Difference in structure
A monobloc system houses most of the equipment in the outdoor unit and sends hot or cold water into the property. A bibloc system is divided into two parts: an outdoor unit and an indoor unit. Refrigerant generally circulates between them, while heat transfer to the water circuit takes place inside the home.
This difference influences virtually the entire installation.
Difference in installation
A monobloc air source heat pump generally has a more straightforward installation because it does not require refrigerant connections between the indoor and outdoor sections, which can reduce labour time and costs.
A bibloc system requires a more specialised installation, as refrigerant work is involved. For this reason, it must be installed by qualified professionals with experience in these systems.
Difference in indoor space requirements
A monobloc system requires less indoor space. This is a clear advantage when there is no plant room available or when a more compact solution is preferred. A bibloc system requires an indoor unit as well as any cylinders or auxiliary equipment. If the property has sufficient space, this is not an issue, but in smaller properties it may influence the decision.
Difference regarding frost risk
In a monobloc system, water circulates between the outdoor unit and the interior of the property. As a result, in colder climates the outdoor pipes must be very well insulated and protected.
In a bibloc system, water generally remains inside the property, which reduces the risk of the hydraulic circuit freezing. For this reason, it may be the more suitable option in areas with severe winters.
Difference in efficiency
It cannot be said that one is always more efficient than the other, because performance depends on the equipment selected, outdoor temperatures, property insulation, flow temperatures and the type of heat emitters.
A well installed monobloc system can be highly efficient, and a well designed bibloc system can be equally efficient. The key is to size the system correctly and adapt it to the actual needs of the property.
Difference in price
A monobloc air source heat pump generally has a more competitive installation cost due to its simpler setup. However, the final price depends on factors such as output capacity, model, hot water cylinder, pipe distances and installation complexity.
A bibloc system may be more expensive to install, but it may also be more suitable for large homes, cold climates or technically demanding installations.
Comparison table of recommended floor area and average COP
| Property floor area | Indicative output | Monobloc air source heat pump | Bibloc air source heat pump | Estimated average COP |
|---|---|---|---|---|
| 50 to 80 m² | 4 to 6 kW | Highly recommended | Recommended if indoor space is available | 3.2 to 4.5 |
| 80 to 120 m² | 6 to 8 kW | Highly recommended | Highly recommended | 3.0 to 4.3 |
| 120 to 180 m² | 8 to 12 kW | Recommended with good design | Highly recommended | 2.8 to 4.2 |
| 180 to 250 m² | 12 to 16 kW | Depends on climate and insulation | Highly recommended | 2.7 to 4.0 |
| More than 250 m² | 16 kW or more | Case by case basis | More flexible | 2.5 to 3.8 |
COP indicates the relationship between the thermal energy generated and the electricity consumed. For example, a COP of 4 means the system can produce 4 kWh of thermal energy for every 1 kWh of electricity consumed, under specific conditions.
In practice, COP varies according to outdoor temperature and the water flow temperature required. This is why a well insulated home with underfloor heating generally achieves better results than a poorly insulated property with old radiators.
Which is better, bibloc or monobloc air source heat pumps?
A monobloc air source heat pump is generally more recommended if you are looking for a simple installation, have limited indoor space, live in a mild or moderate climate and want to minimise work inside the property.
A bibloc air source heat pump may be the better option if you have space for an indoor unit, live in a cold climate, have a large property or require a more flexible and customised installation. In a small or medium sized, well insulated home located in a temperate area, a monobloc system may be sufficient and highly efficient. In a large property with greater energy demand or located in a colder area, a bibloc system may provide greater reassurance.
Before deciding between a monobloc or bibloc air source heat pump, always consider the following:
- Property size.
- Level of insulation.
- Local climate.
- Available indoor space.
- Location of the outdoor unit.
- Type of heat emitters: underfloor heating, radiators or fan coils.
- Domestic hot water demand.
- Installation budget.
In summary, the monobloc option is more compact, straightforward and practical, while the bibloc option is more flexible, technical and better suited to demanding installations. Both can be highly efficient if designed correctly.
