Heating with the air conditioner: when can it replace the heating?

A split air conditioner cools in summer by pumping heat out of the room. In heating mode, it reverses this process: the outdoor unit absorbs heat from the outside air, whilst the indoor unit releases it into the room air. Technically, it is then an air-to-air heat pump. Whether it can replace the central heating system depends less on the unit itself than on the room and what else the heating system has to do.

Even cold outdoor air contains heat. The refrigerant in the outdoor unit evaporates even at very low temperatures and absorbs this heat; the compressor raises it to a higher temperature, and the indoor unit releases it into the room via its heat exchanger. The electricity primarily powers the compressor; the heat itself comes from the air.

The SCOP – the seasonal coefficient of performance – indicates how well this is achieved over the entire heating season. A SCOP of 4 means that, on average over the season, one kilowatt-hour of electricity produces four kilowatt-hours of heat. According to the data sheet, the split systems in the range achieve a SCOP of between 4.0 and 4.7. The EU energy label also states the efficiency class for heating; for the systems in the range, this is A+ or A++.

Each data sheet specifies an operating range for heating. The appliance will operate down to the lower limit; however, the heating capacity decreases as the outside temperature drops.

Information current as of: ACTEC product range, October 2026. The specifications for individual devices can be found on their respective product pages.

Anyone looking to buy an air conditioner primarily for heating should therefore look at the series rated at −25 °C: they offer greater flexibility on cold days and a higher efficiency class.

An air conditioner heats the air in the room where its indoor unit is installed. This determines what it is suitable for:

• Individual rooms: study, converted loft, extension, holiday flat, a room without its own radiator.
• Transition period: in spring and autumn, when the central heating is not yet or no longer intended to be running.
• Multiple rooms: In a multi-split air conditioner, one outdoor unit supplies two to five indoor units; each room can be controlled individually.

It does not replace the heating system where the latter has to do more than simply heat the air in the room:

• An air conditioner does not produce hot water.
• Radiators and underfloor heating are operated using hot water. This is achieved by an air-to-water heat pump, which transfers its heat to the heating water. Whether it is suitable for an older house is explained under ‘Heat pumps in older buildings’; for details on how air-to-air and air-to-water heat pumps differ in other respects, see ‘Air-to-air or air-to-water heat pump?’.
• Entire houses with many rooms can only be heated room by room using indoor units.

Whether a unit can heat a room on its own even on cold days depends on the room’s heating load: this is determined by insulation, windows and location. The specialist firm installing the system can estimate this. For guidance on selecting a unit based on room size, see ‘Which air conditioner for which room size?’; for the split-system units in the range, the heating capacity, according to the data sheet, is equal to or greater than the cooling capacity.

The indoor unit blows warm air into the room. This provides heat differently to a radiator: the air moves, and warm air rises. The fins on the indoor unit direct the airflow; in the case of the Hantech Elegant, for example, the manufacturer states that the air flows downwards so that the heat is distributed evenly. The noisy part – the compressor – is located outside, even when the system is heating.

When the system is in operation, condensation forms on the outdoor unit; in frosty conditions, this thaws intermittently. The water must be able to drain away without causing a footpath to freeze over; the specialist contractor will plan the installation site and drainage as part of the installation.

Electricity consumption can be estimated using the SCOP: heat demand divided by the SCOP gives the electricity consumption. If a room requires 2,000 kWh of heat during the season and the unit has a SCOP of 4, this amounts to around 500 kWh of electricity; multiply this by your electricity tariff to calculate the cost. With a SCOP of 4.7, it would be around 425 kWh.

The SCOP is a standardised average value. In a cold winter, at high room temperatures, or when the appliance frequently operates near the lower limit of its operating range, it requires more electricity. The best way to determine your heating requirements is to refer to previous heating bills for the room or flat.

Split air conditioners are filled with a fluorinated refrigerant. For their sale, Article 11(7) of the F-Gas Regulation (EU) 2024/573 and Section 15(3) of the ChemKlimaschutzV require proof that a certified specialist contractor has been commissioned to carry out the installation. This also applies to Quick-Connect sets. You are responsible for commissioning the specialist contractor yourself; installation is not included in the purchase. You can find out how we request proof of this after you have placed your order under ‘Professional installation of your air conditioner’.

All sets with a heating function are listed under ‘Split air conditioners’; according to the data sheet, Hantech’s H-Plus series heats down to −25 °C. Whether a split air conditioner or a portable unit is more suitable is explained under ‘Monoblock or split air conditioners’.