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.

In short: fixed install or permission-free

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 makes 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 that is 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.

F-Gas: why you may 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.

The permission-free alternatives

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.

Even mobile units call for consideration

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.

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