Split AC in a Rental: Is It Legal, and How Is It Different From a Permission-Free Mobile Split?
A fixed split system and a permission-free mobile split sound similar, but the law treats them very differently. Here is what tenants in Germany can install without asking, and where consent becomes mandatory.
5 min read · Updated July 2026
Renting and wondering whether you can put in a split AC? The honest answer: a permanently installed split system almost always needs your landlord's written consent, while a permission-free mobile unit usually does not. What matters is not the word „split“ but whether someone drills into the building and whether refrigerant is charged on site.
What decides whether you need consent?
The legal hinge is the structural change. As long as a unit needs no drilling, no work on the facade and no work on the refrigerant circuit, it counts as reversible. Your landlord can hardly forbid a reversible device. The moment holes go into the wall, an outdoor unit is bolted to the facade, or a technician charges the refrigerant on site, it becomes a structural measure, and that only happens with permission.
What counts as a fixed split AC?
A classic split system has an indoor and an outdoor unit joined by refrigerant lines. Installing one usually means:
- A technician drills a wall penetration for the lines.
- The outdoor unit is mounted on the facade or balcony.
- The refrigerant circuit is charged and tested on site by a certified technician.
- The change is permanent and only reversible with real effort.
Why is that tricky in a rental?
Drilling into wall and facade plus a fixed outdoor unit is a structural change to the rented property. Without the landlord's consent you take on real risk:
- The landlord can demand removal and restoration of the original condition, potentially at your expense.
- In owner-occupied buildings the owners' association often has to approve the facade change as well.
- The outdoor unit has to meet noise limits, especially toward neighbours.
- Depending on the state building code, and for listed buildings, further conditions can apply.
Why may you not touch the refrigerant circuit yourself?
Fixed split units contain fluorinated greenhouse gases (F-gases). Charging, servicing and disposing of these circuits is EU-regulated and may only be carried out by certified specialists, in Germany under the Chemicals Climate Protection Ordinance (Chemikalien-Klimaschutzverordnung). Piping and filling a split unit yourself is therefore not only a tenancy problem, it is legally off-limits.
Which alternatives are permission-free?
Three device types work without touching the building fabric and therefore usually need no consent:
- Mobile monoblock units: a single unit in the room, with an exhaust hose running through a tilted window or a window seal. No drilling, fully reversible.
- Window AC units: set into the window opening and removed again without lasting damage.
- Permanently sealed mobile split units: indoor and outdoor parts are joined by a factory-filled, sealed line that runs through a window seal. No wall penetration, no on-site charging, no F-gas certificate needed.
The sealed mono-split is the quiet middle ground. It cools more quietly than a monoblock because the compressor sits outside, yet it stays permission-free because nothing is drilled and nothing is piped on site.
What still applies to mobile units?
Permission-free does not mean rule-free. The exhaust hose must not damage the windows, the condensate has to drain properly, and the house rules and usual quiet hours still apply. A quick word with your landlord never hurts, if only to avoid misunderstandings later.
Bottom line: „split“ is not a banned word. What is off-limits without consent is the intervention into the building fabric and the refrigerant circuit. If you rent and want to cool down, a mobile monoblock, a window unit or a sealed mono-split usually gets you there without paperwork. KlimaLegal's Sommer-Abo is built around exactly these permission-free devices, delivery and autumn pickup included.
FAQ
Can I install a split AC in my rental without permission?
A permanently installed split system with a wall penetration and an outdoor unit: no, that needs your landlord's written consent. A mobile, sealed split unit without any drilling: usually yes, because it is not a structural change.
What is the difference between a mobile split and a fixed split unit?
With a fixed split, a technician drills the wall and charges the refrigerant circuit on site. With a sealed mobile split, a factory-filled line runs through a window seal, nothing is drilled and nothing is charged on site. That is why the mobile unit is permission-free.
Do I need my landlord's permission for a mobile air conditioner?
For a purely mobile device, usually not, as long as nothing is damaged and the house rules are respected. A short heads-up to your landlord still creates clarity.
What happens if I fit a fixed split system without consent?
The landlord can demand removal and restoration of the original condition, in case of doubt at your expense. For questions about your specific situation, a tenancy-law advisor can help.
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