AC in a Rental Flat: When You Need the Landlord's Consent, and When You Don't

A plain-language guide to German tenancy law: permission-free mobile and window units versus fixed split systems, which need consent, an F-Gas-certified installer and a removal agreement.

6 min read · Updated July 2026

Summer in Berlin, 34 degrees under the roof, and the same question comes back every year: can you just buy an air conditioner, or do you have to ask the landlord first? The short answer is that it depends on the device. For most portable units you need no consent at all. The moment something gets drilled or bolted to the facade, though, German tenancy law reads differently. Here are the basics, sorted by what actually matters.

The Basic Rule in German Tenancy Law

As a tenant you are allowed to use your flat as intended, and keeping it cool is part of that. What decides the consent question is whether your plan touches the building fabric. Anything you can set up without a structural change, and take away cleanly when you move out, is generally your own business. Once you drill holes in walls or the facade, mount an outdoor unit, or run refrigerant lines through the wall, you change the substance of the flat. That needs the landlord's consent.

ACs That Need No Consent: Portable, Window, Sealed

These device types count as permission-free because they work without any fixed intervention:

• Portable monoblock units: a single unit on wheels that pushes warm air outside through an exhaust hose. The hose runs through a tilted window or a door opening, usually with a fabric or plastic seal. No drilling, no mounting.
• Window units: fitted into the window frame and taken out again after the season.
• Permanently sealed mobile split units (monoblock splits): the indoor and outdoor parts are factory-filled and hermetically closed, so you can hang the outdoor part on the balcony without ever opening the refrigerant circuit.

The common thread: you leave the building fabric untouched and can remove everything without a trace. That is why simply running one of these devices normally needs no permission. You are not entirely off the hook, though, and I'll come to that below.

When You Do Need the Landlord's Consent

Fixed split systems are the classic case where you have to ask first. With them, an outdoor unit hangs on the facade or roof, refrigerant lines are routed through the wall, and the indoor unit is screwed in place. That is an intervention in the building fabric and in the external appearance of the building.

• Landlord's consent: required, and best obtained in writing before anyone drills.
• Certified firm and F-Gas proof: split systems contain fluorinated refrigerants. Under the EU F-Gas Regulation, only certified specialists may open, fill and commission the refrigerant circuit. Installing it yourself is not an option.
• Further approvals: in a building owned as condominiums, a resolution of the owners' association may also be needed, and listed (heritage-protected) facades can require an official permit on top.

If the landlord refuses consent for a fixed system, they often have good reasons, from the look of the facade to structural load and noise for neighbours. There is no automatic right to a permanently installed air conditioner.

What Still Applies Even Without Consent

Permission-free does not mean rule-free. Even with a portable unit, keep a few points in mind:

• Noise and neighbours: the unit, and any outdoor part, must respect quiet hours and the house rules. A device humming on the balcony all night is a fast way to a dispute.
• No permanent alterations: seal the exhaust hose with a window kit instead of cutting a fixed opening into the frame or wall.
• Condensate and moisture: drain any water cleanly so you do not cause damp damage.
• Removal when you move out: portable units you simply take with you. If you received permission for a fixed system, the landlord can require you to restore the original condition when you leave. Settle that in writing beforehand.

How to Go About It

• Classify your device: a portable monoblock, a window unit or a sealed split unit normally needs no consent, while anything involving drilling or an outdoor unit does.
• If you want a fixed system, get the landlord's consent in writing and agree on the removal at the same time.
• Mind noise, condensate and the house rules, whatever device you choose.
• If you are unsure about your specific situation, a quick look at your lease or a bit of legal advice helps.

Anyone who wants to cool down without the whole procedure usually reaches for a permission-free portable unit for the season. That is exactly what KlimaLegal's Sommer-Abo is built around: delivered, set up, and collected again in September, with no drilling and no consent needed.

The rule of thumb stays simple. As long as you change nothing in the building fabric and can take everything away cleanly, an air conditioner in your rental flat normally needs no consent. Once there is drilling, mounting, or a refrigerant circuit to open, the path runs through the landlord and a certified firm. This text is general orientation and does not replace individual legal advice in case of doubt.

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