Are Portable ACs Allowed in a Rented Flat? Why Mobile Units Need No Landlord Consent

As a renter, you can just use a mobile monoblock, a window unit or a sealed split. Here is the legal reason no landlord sign-off is needed, and the point where that stops being true.

5 min read · Updated July 2026

It is 34 degrees in your top-floor Berlin flat, you cannot sleep, and the same question comes up every time: can you set up an air conditioner without asking your landlord? For mobile units, the answer is usually yes. You do not need consent for a portable monoblock, a window unit or a sealed mobile split. Here is why, and the one case where the rules change.

Short answer: mobile units need no consent

A portable monoblock that you stand on the floor and vent through a tilted window is part of the normal, contract-compliant use of your flat. Nothing gets drilled, mounted or permanently attached to the building. When you move out, the unit goes with you and the flat looks the way it did before. Since there is no structural change, your landlord's permission is not legally required.

Why permission is not required (the legal logic)

German tenancy law lets a landlord require consent when you make a structural change to the building, known as a bauliche Veraenderung. That covers anything touching the substance of the property: a wall breakthrough, a mounted outdoor unit, holes in the facade. A mobile device does none of that.

• It is free-standing and fully reversible, so it does not count as a structural alteration.
• Cooling your rented home falls under the intended use you already pay rent for.
• A blanket clause banning any cooling at all is generally hard to enforce against a device that causes no damage and no real disturbance.

Permission-free vs. permit-required: the device type decides

The line has little to do with whether the thing counts as an air conditioner. It comes down to whether installing it changes the building. That sorts the options into two groups.

• Permission-free: portable monoblock units, window air conditioners, and permanently sealed mobile split units. None of these cut into the wall or hang hardware on the facade.
• Permit-required: fixed split systems with an outdoor unit bolted to the exterior wall. That means a wall breakthrough and mounted hardware, which is a structural change. It needs the landlord's consent, usually a certified installer, and in an owners' association a formal resolution.

F-Gas: why you can plug in a monoblock yourself

Mobile monoblocks and sealed mobile splits arrive hermetically closed and pre-filled with refrigerant. There is no open refrigerant circuit for you to connect, so no certified technician and no F-Gas handling on your side. You unpack it, position the exhaust hose and plug it in. Fixed split systems work the other way round: the refrigerant lines are opened during installation, which under the EU F-Gas Regulation has to be done by a certified firm. That is one more reason mobile units stay so easy to live with.

What to keep in mind anyway

Not needing consent does not give you licence to cause damage or annoy the building. A few sensible habits keep you well on the safe side.

• Do not damage the window. Route the exhaust hose through a tilted window with a fabric or panel seal instead of drilling the frame.
• Be considerate of neighbours. House rules can cover noise and nuisance, so do not run a loud unit at night against a shared wall.
• Handle condensate properly. Do not let water drip onto a balcony, the facade or a neighbour below.
• Mind the electricity. Monoblocks draw real power, so use a proper socket rather than a daisy-chained extension lead.

The bottom line: if the unit is mobile and leaves no mark on the building, you are within your rights as a renter. Save the landlord conversation for fixed split systems, where a permit genuinely applies. And if you would rather not own the hardware at all, some providers offer seasonal rentals where a suitable monoblock is delivered and collected again in autumn, so the whole thing stays consent-free and nothing lingers in the flat afterwards.

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