Air conditioning that also heats: summer cooling, winter heating and when the 6% VAT rate applies

How an air conditioner heats

A split system has an outdoor unit with a compressor and an indoor unit on the wall of the room, connected by two refrigerant pipes. In cooling mode it moves heat from the room to the outside air. Reverse the cycle and it moves heat from the outside air into the room. Even at 0 degrees the outdoor air contains usable heat, and current units keep heating down to about minus 15 degrees, with reduced output.

Efficiency is expressed as a coefficient of performance. A typical COP of 3.5 in heating mode means 1 kWh of electricity delivers 3.5 kWh of heat. A 2.5 kW heating unit therefore draws about 0.7 kW. At 0.30 euro per kWh that is about 0.21 euro per hour of full-power heating, compared with about 0.75 euro for a 2.5 kW electric radiator. Against a gas boiler the difference is smaller but still in favour of the air conditioner for a single room, and the capital cost is far lower than a full heat pump on radiators.

The limits are honest ones. An air-to-air unit heats the room it is in and the air around it; it does not provide hot water, and it is not a substitute for insulation. In a well-insulated house it can be the main heating. In a poorly insulated one it works best as a supplement in the rooms you use most.

Single split or multisplit

A single split serves one room: a bedroom, a home office, a living room. A multisplit has one outdoor unit and two to five indoor units, each controlled separately, which keeps the facade tidy and the electrical work to one circuit. Indoor units are sized on the room: roughly 2.5 kW for up to 25 m2, 3.5 kW for 25 to 35 m2 and 5 kW for a large living space, adjusted for insulation, glazing and orientation.

The installed price depends on the brand, the capacity, the number of indoor units, the pipe length, the mounting of the outdoor unit and the electrical connection, and after the site visit you receive a fixed price in the quote. A unit that heats needs a dedicated circuit in the fuse box with its own protection, and the modified installation is inspected under the AREI like any other new circuit.

When the 6% VAT rate applies

Belgium charges 21 percent VAT on most building work, but renovation work on a private home that is at least ten years old is charged at 6 percent. The installation of air conditioning falls under that rule, together with electrical, plumbing and heating work. For heating installations there is one important exception since 2025: systems that run on fossil fuels no longer qualify in renovation. A heat pump, including an air conditioner that heats, is fully electric and stays at 6 percent.

The conditions are:

• The home was first occupied at least ten calendar years before the invoice date; a home occupied in 2016 qualifies for invoices from 1 January 2026
• After the work the building is used mainly or exclusively as a private home, not an office or a shop
• The installer supplies and installs; material you buy yourself is always 21 percent
• The work is fixed to the building: a wall-mounted split qualifies, a mobile unit does not
• The unit heats; cooling-only equipment is excluded

The invoice and a worked example

If the conditions are met, the installer applies the rate on the invoice and asks you to sign a short declaration that the home is more than ten years old and used privately. It is not an automatic right: we confirm at the site visit whether it applies to your home. If the rate turns out to be wrongly applied, the installer can issue a corrected invoice at 21 percent, so check the age of the house before you sign the quote.

The effect is easy to calculate: on an invoice of 1,000 euro excluding VAT, 6 percent VAT adds 60 euro and 21 percent adds 210 euro, so the reduced rate saves 150 euro for every 1,000 euro of work. For homes younger than ten years, Belgium reintroduced a 6 percent rate for fully electric heat pumps from 1 January 2026 for five years, which also covers an air-to-air unit used for heating.

Flanders has no premium for an air conditioner as such. The Mijn VerbouwPremie covers an air-to-air heat pump only when it is the main heating of a home without any central heating system, and the amount depends on income and building type.

Running it well

Two habits keep the running cost low. Set a steady temperature rather than switching on and off; an inverter compressor idles at a few hundred watts to hold 21 degrees. And keep the indoor filter clean, which takes two minutes a month and preserves the COP. A yearly service covers the filters, the condensate drain and the outdoor unit.

In heating mode an air conditioner draws power at the same moments as the rest of the house, so it adds to your monthly peak under the capacity tariff; a 0.7 kW draw is modest, but three units defrosting at once in a cold snap is not. Roakus-E installs air conditioning with the electrical circuit, the inspection and the VAT statement on the invoice handled in one job, and applies the 6 percent rate once the site visit confirms that your home qualifies.