Air conditioners for rented flats compared

Under German tenancy law, a portable air conditioner counts as a household appliance, like a fridge: you can set it up and use it without asking. An exhaust hose in a tilted window is not a structural alteration. A permanently installed split system is a different matter – core drilling and an outdoor unit on the façade require your landlord's consent and, in a condominium, additionally that of the owners' association (WEG).

Borderline cases are the outdoor units of mobile split systems on a balcony or windowsill: they change nothing about the building but are visible and audible. In practice this is unproblematic as long as neighbours are not disturbed and nothing is permanently mounted. Noise limits are considerably stricter at night than during the day – use night mode and do not place the outdoor unit directly below your neighbours' bedroom window.

For a single room and the occasional hot day, a monoblock is the cheapest option. If you cool regularly or are sensitive to noise, you are better off with a mobile split such as the Midea PortaSplit: quieter, more efficient and easy to take with you when you move out.

Place the unit as close to the window as possible so the exhaust hose or refrigerant line stays short. A monoblock needs about 50 cm of clearance from the wall to draw in air; a mobile split wants its outdoor unit in the shade with free air circulation. Close the door to the rest of the flat, keep the shutters down during the day and use the timer so the unit starts half an hour before you get home. And: better to hold 25 °C than force 21 °C – it saves electricity and spares the neighbours.