Look at the room first
Measure floor area and ceiling height. Note direct sunlight, glazing, shading and heat-producing equipment. A home office under the roof has different cooling needs from a shaded bedroom of the same size.
| Criterion | Information to collect |
|---|---|
| Room | Area, height, sun, occupancy |
| Window | Type, dimensions, compatible kit |
| Cooling | kW or BTU/h plus test method |
| Electricity | Electrical input, not cooling output |
| Noise | Quantity, mode, distance, method |
| Practical use | Weight, clearances, filter, drainage |
Plan a route for the heat to escape
A compressor-based portable air conditioner rejects heat outdoors. Its exhaust hose and window kit are part of the installation. A water-based evaporative cooler works differently and is not a substitute for an air conditioner. Check compatibility with casement, tilt-and-turn or sliding windows before buying.
Compare the complete setup
Look at cooling capacity, electrical input and noise figures measured on a comparable basis. Include the window kit, dimensions, weight, condensate handling and filter access in your checklist. Castors help on one floor; carrying a unit up stairs is another matter.
Keep heat out before cooling
Close external shading before sunlight heats the glass. Ventilate when it is cooler outside, then close windows during cooling. Treating one clearly defined room is more predictable than trying to cool an entire flat through open doors.
Single hose, dual hose or split?
A single-hose portable unit may use some room air when rejecting heat outdoors, encouraging replacement air to enter. A dual-hose design separates the air paths more, depending on its construction. A split system puts part of the equipment outside. Hose count alone is not a ranking: compare compatible capacity ratings and the complete installation.
Measure before ordering
Photograph the window and measure its opening. Identify an electrical outlet suitable for the manufacturer’s instructions. Include required clearances in the floor footprint. Ask for the compatible window kit’s exact reference and contents. Check condensate handling for your intended mode: cooling, dehumidifying and storage may require different steps.
A decision example for a rented flat
Imagine a 30 m² room with a tilt-and-turn window, used as an office by day and a bedroom at night. Beyond capacity, the hose route, evening noise and kit storage all matter. First establish whether a reversible installation is possible. Then compare two or three complete data sheets rather than two online shop headlines.
What to request from the seller
Ask for documents matching the exact model: cooling capacity, electrical input, acoustic results with conditions, accessories and instructions. “Up to 45 m²” without height, sun exposure or test conditions is not a promise for your home. Record missing information as “not specified” instead of turning an omission into an assumed product advantage.
Turn the guidance into a room plan · 1
Choose your priority room and measure its area and height. Total apartment floor area does not describe airflow between closed bedrooms.
Turn the guidance into a room plan · 2
Sketch the route outdoors. A window opening, hose route and suitable seal are part of the plan. Portable does not mean free of installation constraints.
Turn the guidance into a room plan · 3
Estimate demand before comparing appliances. The FREATH ONE check compares your demand with its two documented capacities, 12,000 and 14,000 BTU, and separately exposes missing details about the final installation.
Sources and methodology
These sources explain the technical context. They do not validate FREATH ONE or our calculator assumptions.
U.S. Department of Energy — Portable Air ConditionersOFEN / BFE — Étiquette-énergie / EnergieetiketteMieterverband — tenant rights and air conditioning (in German)