Air conditioners with heating compared

In heating mode the unit reverses the refrigerant cycle: it extracts heat from the outside air and releases it indoors. In mild weather it delivers 2.5 to 3.5 kWh of heat per kilowatt hour of electricity, depending on the model – an electric fan heater manages exactly one. In a monoblock this process runs via the exhaust hose (cold air is then blown outside); in a mobile split it runs via the outdoor unit.

The colder it is outside, the less heat the air contains. Below roughly 0 to 5 °C, output drops sharply and many units switch off. For spring and autumn the heating function is still a cheap supplement, especially while the central heating is still off.

It makes sense if the unit stays in one room anyway and you want to heat that room in spring and autumn – a home office, a garden room or a hobby room, for example. No portable unit can replace a gas or oil heating system in winter. The extra cost over a cooling-only unit is usually 50–150 euros.

Heating is standard on mobile splits: the Midea PortaSplit and the Remko RKL 495 DC both heat as heat pumps. On monoblocks it is a feature that often shows up in the model name as “H”, “Heat” or “4-in-1” – for example the Trotec PAC 3500 X, Klarstein Max Breeze Smart or De'Longhi Pinguino PAC EX Heat. Check the heating output in kW on the spec sheet: it is usually slightly above the cooling output because the compressor's waste heat is used as well.