A mobile air conditioner is one of the few real cooling upgrades a renter can make without permission or permanent changes — if you set it up correctly. The whole job takes minutes and needs no tools. Here's exactly how, in order.
Step 1: Position the unit near a window
Place the air conditioner on a level surface close to the window you'll vent through, with a little clearance around the air intake. The shorter and straighter the exhaust hose run, the better it performs — a long, kinked, or sagging hose lets heat soak back into the room. Keep it upright, and if you've just moved it, let it stand for a while before switching on.
Step 2: Attach the exhaust hose
Connect the hose to the unit's outlet and extend it to the window. This hose carries the heat the AC removes to the outside. Avoid stretching it across the whole room or looping it — keep it as short and direct as possible so the hot air leaves quickly instead of warming the hose and re-heating your space.
Step 3: Fit a no-drill window sealing kit
This is the step that makes or breaks the cooling. A window sealing kit is a fabric or rigid-panel insert that fits your window opening, lets the hose pass through, and seals the rest of the gap. Without it, the hot air you push outside simply flows back in around the hose, and the room never cools. No-drill kits fit most tilt or sliding windows, install in minutes, and remove without a trace — ideal for renters.
Step 4: Handle condensate
As it cools, the unit removes moisture from the air. Many models self-evaporate most of this out through the hose; others collect it in a tray or tank you empty occasionally, more often in humid weather. Check your manual so a full tank doesn't shut the unit down on the hottest afternoon.
Step 5: Seal the room and run it
Close the door and any other windows so the unit cools a contained space rather than fighting the whole flat. Set a timer or sleep mode for overnight use, and shade the windows during the day so the AC isn't battling direct sun. A sealed, shaded room lets a modest unit keep up easily.
Staying within tenancy rules
Everything here is removable — no drilling, no fixed installation, no changes to the building. That's what keeps a mobile AC within typical German rental rules and protects your deposit. If your lease has unusual clauses, check them, but portable cooling vented through a no-drill kit is normally fine.
When you're ready to buy, make sure you choose a unit that's actually available: check renter-friendly mobile ACs in stock near you and reserve one for pickup.