Air-to-air heat pumps are gaining ground in Belgian homes. Long regarded primarily as reversible air-conditioning systems, they are now increasingly used as genuine heating solutions. The principle is simple: recover energy naturally present in the outside air and use it to heat the air inside the home.<\/p>\n\n\n\n
In a country such as Belgium, where winters are generally moderate but heating needs remain significant for several months, this technology can be particularly attractive. It can also cool the home during hot periods, an advantage that is becoming increasingly important as summer heatwaves become more frequent.<\/p>\n\n\n\n
However, an air-to-air heat pump is not automatically the best solution for every home. Insulation, room layout, unit placement, noise levels, electricity consumption and regional regulations all need to be considered before making a choice.<\/p>\n\n\n\n
An air-to-air heat pump works on a principle similar to a refrigerator, but in reverse when it is heating the home.<\/p>\n\n\n\n
The outdoor unit extracts heat from the air. Even when the outside temperature is low, the air still contains thermal energy. A refrigerant circulates through the system and transports this energy. The compressor then raises the temperature of the refrigerant before the heat is distributed through the home by one or more indoor units.<\/p>\n\n\n\n
Unlike an air-to-water heat pump, the heat is not transferred to water circulating through radiators or underfloor heating. Instead, it is distributed directly into the air in the different rooms.<\/p>\n\n\n\n
Most modern units are reversible. In summer, the cycle can operate in the opposite direction. Heat inside the home is then expelled outdoors, allowing the rooms to be cooled.<\/p>\n\n\n\n
This dual function explains why the terms \u201cair-to-air heat pump\u201d and \u201creversible air conditioning\u201d are often used for systems that are technically very similar.<\/p>\n\n\n\n
Belgium\u2019s climate is fairly well suited to heat pumps that use outside air as their energy source. Winter temperatures are relatively moderate for much of the heating season, allowing a correctly sized installation to operate at an attractive level of efficiency.<\/p>\n\n\n\n
Heat-pump performance is generally expressed using COP and especially SCOP, which takes efficiency over an entire heating season into account.<\/p>\n\n\n\n
In simple terms, a COP of 4 means that a heat pump supplies around four units of heat for one unit of electricity consumed under the stated test conditions. In reality, performance changes continuously according to the outdoor temperature, the indoor temperature requested and how the installation is operating.<\/p>\n\n\n\n
The colder it is outside, the harder the machine has to work to recover and transfer heat. Its efficiency therefore falls when the outdoor temperature drops significantly.<\/p>\n\n\n\n
This does not mean that an air-to-air heat pump automatically stops working when it freezes. Modern systems can operate at temperatures well below zero. The real issue is whether their output and efficiency remain sufficient for the building\u2019s needs during the coldest periods.<\/p>\n\n\n\n
In a well-insulated home, a correctly sized air-to-air heat pump can become the main heating system. In an older, poorly insulated building with major heat losses, the economic case will be much less obvious.<\/p>\n\n\n\n
Brussels Environment also stresses the importance of considering a building\u2019s insulation when planning a heat pump.<\/p>\n\n\n\n
An air-to-air system can have one indoor unit or several.<\/p>\n\n\n\n
In a single-split configuration, one outdoor unit is connected to one indoor unit. It is an attractive solution when the main aim is to heat or cool a large living room, an office, a compact flat or an extension.<\/p>\n\n\n\n
In a multi-split installation, one outdoor unit supplies several indoor units located in different rooms. This configuration is better suited when you want to provide a significant share, or even all, of the home\u2019s heating.<\/p>\n\n\n\n
The choice should be based on the layout of the home. Heat from a wall-mounted unit does not pass efficiently through several closed doors. Installing a very powerful unit in the living room and expecting it to heat every upstairs bedroom evenly therefore often leads to disappointing results.<\/p>\n\n\n\n
A survey of the home makes it possible to determine the required output and the number of indoor units that are genuinely useful.<\/p>\n\n\n\n
There is no single answer. Consumption depends on the area to be heated, insulation, the desired indoor temperature, the weather, the efficiency of the unit and the occupants\u2019 habits.<\/p>\n\n\n\n
A heat pump does not, however, create all its heat from the electricity it consumes. A large proportion of the thermal energy is taken from the outside air. That is precisely what allows it to be much more efficient than a conventional electric resistance heater.<\/p>\n\n\n\n
To assess an installation properly, it is therefore better to look at its SCOP rather than focusing only on its instantaneous electrical power.<\/p>\n\n\n\n
It is also important to avoid a fairly common mistake: directly comparing a gas bill with an electricity bill by looking only at the price per kilowatt-hour. A boiler and a heat pump do not use energy with the same efficiency. The final heating cost depends on how many kilowatt-hours of electricity are needed to produce the amount of heat actually required by the home.<\/p>\n\n\n\n
Combining a heat pump with solar panels can also be worthwhile. This does not mean the heating will be powered entirely by the sun, because solar production is lower in winter. It can nevertheless cover part of the system\u2019s annual electricity consumption.<\/p>\n\n\n\n
One of the major strengths of an air-to-air heat pump is how simple it is to install compared with some other technologies.<\/p>\n\n\n\n
There is no need to dig up the ground for geothermal probes or install a complete water-based heating circuit. This is particularly useful in a home fitted with direct electric radiators or in a building where installing a new hydraulic network would be complex and expensive.<\/p>\n\n\n\n
Heating up is also quick. As soon as the unit starts, warm air is blown into the room. Room-by-room control can provide great flexibility, particularly with a multi-split installation.<\/p>\n\n\n\n
Another obvious advantage is that the same installation can cool the home in summer.<\/p>\n\n\n\n
Finally, when it replaces heating that runs directly on gas, heating oil or electric resistance, a correctly sized heat pump can help reduce primary energy consumption and the emissions associated with heating.<\/p>\n\n\n\n
The first point concerns how heat is distributed. Some people prefer forced-air heating less than underfloor heating or radiators. Air movement therefore needs to be managed carefully and the indoor units positioned correctly.<\/p>\n\n\n\n
Noise also needs to be taken seriously. A good modern heat pump can be discreet, but a poorly positioned outdoor unit can become a nuisance for residents or neighbours, particularly in a dense urban environment.<\/p>\n\n\n\n
The location should therefore not be chosen solely on the basis of ease of installation. Distance from bedrooms, neighbouring windows and property boundaries deserves careful consideration.<\/p>\n\n\n\n
In cold, damp weather, the outdoor unit can also build up frost. The system then automatically starts a defrost cycle. This is normal operation, but indoor heat output may be temporarily reduced during the cycle.<\/p>\n\n\n\n
Finally, an air-to-air heat pump does not normally produce domestic hot water. A separate solution is therefore needed for showers, baths and hot water in the kitchen.<\/p>\n\n\n\n
Installing an efficient heat pump in an energy-inefficient building does not solve the building\u2019s fundamental problem.<\/p>\n\n\n\n
The faster a home loses heat through the roof, walls, windows and air leakage, the greater the output required. The heat pump will have to run more and its electricity consumption will increase.<\/p>\n\n\n\n
Before installation, it therefore makes sense to examine roof, wall and floor insulation, the quality of the glazing and the overall airtightness of the home.<\/p>\n\n\n\n
This does not necessarily mean that a house must reach new-build energy standards before an air-to-air heat pump can be installed. In renovation projects, the key is to find the right balance between improving the building envelope and sizing the heating system.<\/p>\n\n\n\n
This is where it is particularly important to distinguish between Flanders, Wallonia and Brussels. The rules are not the same.<\/p>\n\n\n\n
In Flanders, air-to-air heat pumps may be covered by Mijn VerbouwPremie. Since 1 March 2026, however, an air-to-air heat pump whose active cooling function has not been permanently disabled can only qualify if it is the home\u2019s sole central-heating system and the property is completely free of fossil-fuel equipment for heating, hot water and cooking.<\/p>\n\n\n\n
The amounts vary according to income category and applicant profile. For an air-to-air installation, reference amounts include \u20ac600 for certain owner-occupiers in income category 4, \u20ac450 in category 3 and \u20ac300 for several other categories for applications submitted from 1 March 2026. Caps linked to the invoice amount also apply.<\/p>\n\n\n\n
As the conditions change regularly, it is advisable to check the exact situation on the official Flemish Region page before ordering the installation. View Mijn VerbouwPremie for heat pumps<\/a><\/p>\n\n\n\n In Wallonia, the situation is different. Official documentation from the Public Service of Wallonia states that heat pumps that release thermal energy into the air are not eligible for the Habitation grant intended for heating heat pumps. A residential air-to-air heat pump therefore does not qualify for this grant.<\/p>\n\n\n\n The temporary Walloon scheme for 2025\u20132026 also provides that the relevant applications must be submitted no later than 30 September 2026.<\/p>\n\n\n\n