Portable air conditioning in a rented flat

What actually needs permission — and what does not

The useful distinction is not “air conditioner: yes or no”. It is whether the building changes.

Normally no permission needed: a free-standing monoblock unit standing on the floor, its hose led out through a window you are entitled to open, and a seal that is fitted and removed without tools or residue. Nothing is drilled, nothing is fixed, and the flat is returned exactly as it was.

Normally permission needed: anything that puts a hole in the fabric — a core drill for a split system, a bracket for an outdoor unit on the façade or balcony, a permanent condensate outlet, or a fixed pane replacing the glazing. These change the building and, in many buildings, also affect the shared parts, which is a separate agreement again.

Rules differ by country and by contract. The two lines worth finding in your own agreement are the clause on alterations and any clause on the appearance of the façade or balcony. This is a practical guide, not legal advice.

The reversible setup, in practice

A rental-safe installation has three parts, none of which leaves a mark:

• The unit: a monoblock. Everything with an outdoor unit implies mounting hardware. A quick-connect split is the exception, but it still needs somewhere legitimate to put the outdoor half.
• The opening: a fabric seal kit for a tilted or turned window, or a cut panel. Our tilt-and-turn guide covers the window type most of continental Europe has, and there is a separate one for roof windows.
• The condensate: most units evaporate it, some collect it in a tank. Neither requires a drain. If yours drips, see why a portable AC leaks water before you start looking for a pipe route.

Sealing without wrecking the frame

This is where deposits are actually lost. The seal is harmless; the tape is not always. Adhesive left on a painted or lacquered frame through a hot summer bonds hard, and it can take the finish with it when removed.

Two habits avoid it: choose a kit that clamps into the reveal rather than sticking to it, and if you do use adhesive, put it on the seal rather than on the frame and remove it at the end of the season instead of the end of the tenancy. Working out the length you need first also stops you buying a kit that has to be forced into place — the arithmetic is on the window seal guide.

Electricity, noise and the neighbours

Two practical constraints come up in flats more than in houses.

The circuit. A portable unit draws on the order of one to one and a half kilowatts. That is fine on its own, but a shared kitchen circuit already carrying a kettle and a microwave is not a good place to add it. If a fuse trips repeatedly, move the unit to a different circuit rather than assuming the unit is faulty.

The neighbours. The exhaust hose is the loud end and it hangs outside, often a few metres from someone else's open window. Quiet hours exist in most countries with the exact times set locally. Point the hose away from adjacent windows, use the night or sleep setting, and the common complaint disappears before it is made.

If the answer is no

Some tenancies genuinely do prohibit it, and some flats have no window that can take a hose at all. Neither is the end of the topic.

Evaporative coolers need no exhaust, but they add humidity and only shift how the air feels — the honest comparison is in portable AC versus air cooler. Beyond that, the measures that need no permission at all are the ones that keep heat out in the first place: external shade where it is allowed, ventilating in the cold hours, and closing internal doors during the day. Our no-installation cooling guide collects them.

Frequently asked questions

Do I need my landlord's permission for a portable air conditioner?
For a free-standing monoblock unit that vents through a window you open anyway, usually not — nothing is altered permanently. Permission questions start where the building fabric changes: drilling a wall for a split unit, a permanent bracket, or a hole for a condensate pipe. Rules differ by country and by contract, so read the clause on alterations in yours; this guide is not legal advice.

Can I use a portable air conditioner without drilling anything?
Yes. A fabric window-seal kit closes a tilted or turned window around the exhaust hose and is fitted with hook-and-loop tape or clamped in place. A cut acrylic or plastic panel does the same job more rigidly. Both come out again without a trace, which is exactly what you want in a rented flat.

Will a window seal damage the window frame or my deposit?
The seal itself will not; the adhesive can. Sticky tape on a painted or lacquered frame can lift the finish when it comes off, especially after a summer of heat. Prefer kits that clamp into the opening, or apply the adhesive to the seal and not to the frame, and take it down before the tape has baked on for a whole season.

What about the noise and my neighbours?
A monoblock unit is loud enough to be heard through an open window — that is where the exhaust and the compressor are. Most countries have quiet hours in the evening and at night, with the exact times set locally, and a hose hanging out of a window towards a neighbour's bedroom is the usual source of complaints. Pointing the exhaust away from adjacent windows and running the unit on its night setting solves most of it.