Buying a portable air conditioner: PortaSplit, monoblock or split system?

Mobile split (e.g. Midea PortaSplit): around 3.5 kW of cooling, indoor unit about 39 dB in silent mode, no installation, portable, energy class A++/A+, suitable for tenants, guide price in the high three figures.

Monoblock: 2.6–3.5 kW, about 55–65 dB, no installation, portable, energy class A/A+, suitable for tenants, guide price in the mid to high three figures.

Permanently installed split system: 2.5–7 kW, 20–40 dB indoors, installed by a specialist, not portable, energy class A++/A+++, for tenants usually only with the landlord's consent, four-figure price plus installation.

Cooling capacity must match the room size: roughly 60–100 W per m² – 12,000 BTU (3.5 kW) covers about 35–45 m². In a mobile split the compressor sits in the indoor unit and can hum; only the hot condenser unit stands outside. Even so, it is usually quieter than a monoblock, which keeps all the waste heat inside the room.

The Midea PortaSplit is popular and often sold out during heatwaves. On our home page you can see the live status of DIY store chains in Germany, Austria and Switzerland, plus in-store stock on the map. Proven alternatives are the Remko RKL 495 DC (a mobile split with more power) or monoblock units from Comfee and De'Longhi.

The rule of thumb of 60–100 W per square metre is a starting point, not a law. Use the upper value if the room is under the roof, has large south- or west-facing windows, holds a lot of equipment or people, or has a ceiling higher than 2.60 m. The lower value is enough in well-insulated new buildings with external blinds. So a 20 m² ground-floor bedroom needs about 1.5 kW (5,000 BTU), while a 35 m² living room under the roof needs more like 3.5 kW (12,000 BTU).

Too little capacity is the most expensive mistake: the unit runs at full load constantly, gets loud, uses a lot of power and never reaches the target temperature on hot days. Slightly too much capacity, on the other hand, does little harm – modern units cycle or throttle down. If in doubt, go one class bigger.

Manufacturers usually state the sound power level according to EU regulations – that is the total energy radiated, not what you hear two metres away. The sound pressure level at your ear is typically 8–10 dB lower. Figures are only comparable when measured the same way, so read the small print. As a guide: 40 dB is a quiet library, 50 dB a quiet conversation, 60 dB a conversation at normal indoor volume.

For bedrooms, what counts is the night-mode figure, not the best value on the spec sheet. Monoblocks are usually at 48–55 dB there, the PortaSplit at about 39 dB in silent mode. If you are very sensitive to noise, cool the room before bedtime and then switch off – or choose an inverter unit that keeps running quietly instead of audibly switching on and off.

The energy label for portable air conditioners ranges from A+++ to D; the key figure is the EER (Energy Efficiency Ratio): cooling output divided by power input. An EER of 2.6 corresponds to class A, from about 3.1 you get A+. Mobile splits achieve A++ and better because the waste heat stays outside. Over a summer, a better EER can easily make a 20–30% difference in electricity costs.

R290 (propane) has become the standard refrigerant: climate-friendly, efficient and effectively mandatory for monoblocks since 2025 under the EU F-gas rules. Older units with R410A or R32 are not banned, but are harder to repair when they fail because refrigeration technicians increasingly avoid the old refrigerants. If you are buying new, go for R290 – or, with the PortaSplit, wait for the 2027 generation, which also switches to propane.

A monoblock is best placed right by the window with a short, straight hose; every metre of hose and every bend costs output because the hot hose radiates heat back into the room. A fabric window seal (tilt windows) or a sealing panel (sliding and casement windows) stops warm air from flowing back in – without a seal, a third of the cooling capacity is wasted. With a mobile split, the outdoor unit hangs on the windowsill or stands on the balcony; it needs shade and free air circulation, and the flat line fits through the tilted window sash.

Three questions decide it: how many days a year do you really need cooling? Should the unit run in the bedroom at night? Will you still live in this flat in two years? Answer honestly and you will almost always end up with one clear type of unit – and avoid the bad buy that ends up in the cellar: