Which AC Can You Install as a Renter Without Permission?

Mobile monoblocks, window units and sealed mobile splits versus fixed split systems: a clear yes/no list for renters in Germany.

5 min read · Updated July 2026

The summer gets hot, your apartment gets hotter, and the hardware store is full of air conditioners you can simply carry home. But are you actually allowed to set up an AC as a tenant without asking your landlord first? For most portable units the answer is yes. What matters is not how cold the device gets, but whether you change anything structural in the flat to run it. Here is the clear yes/no list.

The short yes/no list

In German tenancy law the dividing line is the bauliche Veränderung, a structural change to the building. As long as your setup is reversible and leaves no permanent mark, you generally do not need the landlord's consent. These devices are usually fine:

Mobile monoblock AC (one housing, exhaust hose out of a tilted window): yes, permission-free
Window unit, fitted reversibly without altering the window or frame: usually yes
Mobile split unit with a factory-sealed, pre-filled refrigerant circuit: yes, permission-free

You do need permission for one category:

Fixed split system with an outdoor unit mounted on the facade and lines drilled through the wall: no, not without written landlord consent

Mobile monoblock units: the simplest case

A monoblock is a single box on wheels. The warm exhaust air leaves through a hose that you clip into an open or tilted window with a seal kit. Nothing is drilled, nothing is glued, and you can roll it into the basement in October. Because there is no structural change and no refrigerant to handle, this counts as normal contractual use of the flat, and your landlord has little basis to forbid it. The trade-offs are practical rather than legal: the hose lets some warm air back in, and a single unit is louder than a split. But on the permission question, a monoblock is the safe bet.

Window units: fine as long as nothing is rebuilt

Window air conditioners sit in the window opening, often held by a bracket in a tilted sash. If the unit is fitted reversibly and you can remove it without a trace, it sits on the same footing as a monoblock and needs no consent. The moment you cut the frame, replace glazing or fix the unit permanently into the window, you have made a structural change, and that does need the landlord's approval. Keep it removable and you keep it permission-free.

Sealed mobile split units: quiet and still permission-free

A mobile split has an indoor and a smaller outdoor part connected by pre-filled lines. The version that stays permission-free has a hermetically sealed, factory-charged refrigerant circuit with quick-connectors. Because the refrigerant is sealed at the factory, no certified F-Gas technician is required to set it up, so you can install it yourself. Run the connection lines through a tilted window and stand the outdoor part on the balcony floor, and the setup stays reversible. The one thing that flips it into permission-required territory is drilling: the moment you bore a hole through the wall for the lines or bolt the outdoor unit to the facade, it becomes a structural change.

When you really do have to ask: fixed split systems

A classic fixed split system is a different animal. The outdoor unit is bolted to the facade, the refrigerant lines run through a drilled wall opening, and the refrigerant circuit is opened and filled on site. Under the EU F-Gas Regulation (517/2014) this refrigerant work must be done by a certified specialist with the proper Sachkundenachweis, so it is not a DIY job. On top of that, an outdoor unit on the facade changes the building's appearance and its substance, which means you need the landlord's written consent, and in a condominium (WEG) usually the owners' approval as well. Listed buildings (Denkmalschutz) add another layer. In short, a fixed split is never permission-free for a tenant.

Permission-free, but these rules still apply

Even when you do not need consent, a few obligations stay in force:

Keep it reversible: no drilling, no permanent fixtures, no damage to the building
Respect quiet hours and neighbours: outdoor and window noise is limited, especially between 10 pm and 6 am and on Sundays
Manage the condensate water so it does not run onto the facade or a neighbour's balcony
Do not block windows that serve as escape routes for good
Seal the window opening properly, both for security and to avoid wasting the cooling
Check the house rules (Hausordnung) and, for older buildings, any Denkmalschutz status
Remove the device and restore the window when you move out

This guide explains the general rules and is not legal advice. If your lease, house rules or building situation is unusual, check the specifics before you buy.

For most renters in Germany the picture is reassuring: a mobile monoblock, a reversibly fitted window unit or a sealed mobile split can go up in your flat without a landlord's signature, as long as you stay reversible, stay quiet and take it with you at the end. The line to remember is simple. Nothing drilled, nothing fixed, no permission needed. Anything bolted to the facade or run through the wall means you ask first. If you would rather skip the choosing and the carrying, you can also rent such a permission-free device for the season instead of buying one.

FAQ

Can my landlord forbid a portable air conditioner?

For a reversible mobile device with no drilling and no structural change, the landlord generally has little basis to forbid it, because it counts as normal contractual use of the flat. It looks different if the setup causes noise complaints, damages the building or blocks an escape route. A fixed split system with an outdoor unit is another matter and does need consent.

Do I need an F-Gas certificate for a mobile split unit?

Not for a mobile split with a hermetically sealed, factory-charged refrigerant circuit. Because the refrigerant is sealed at the factory and you never open the circuit, no certified F-Gas technician is needed and you may install it yourself. A fixed split system, where the circuit is opened and filled on site, does require a certified specialist under the EU F-Gas Regulation.

Do I have to drill the wall to run the exhaust or lines?

No. Monoblocks vent through a hose you clip into a tilted window, and sealed mobile splits run their lines through the same tilted window with the outdoor part standing on the balcony floor. As long as you avoid drilling and permanent fixtures, the setup stays reversible and permission-free. Drilling through the wall turns it into a structural change that needs the landlord's approval.

Should I tell my landlord even if I do not need permission?

You are not legally required to for a reversible mobile device, but a short heads-up is smart. It avoids misunderstandings, keeps the relationship easy and gives you a chance to confirm there is nothing unusual in the house rules. It is courtesy, not a permission request.

Want cool without the hassle?

KlimaLegal rents you a permit-free AC for the summer — delivered, set up, and collected in September. No deposit.

Secure your spot