These solve the same core problem — cooling a room — through very different installation approaches, and the right choice depends heavily on your window and how permanent you want the setup to be.
Portable units are the flexible default here
A unit like the Dreo AC318S vents through a hose and a temporary window kit, moves between rooms, and needs no permanent fitting. For renters or anyone not committing one window to cooling permanently, this is the more practical format.
Window units are a bigger commitment — and a real caveat
The window/monobloc units we’ve reviewed, including the MilleLoom 5,000 BTU, are built primarily around North American sash windows and electrical specifications. Read our dedicated window air conditioner guide before choosing this format if you’re in Europe — the voltage and window-fit issues are real and specific.
Noise and footprint differ too
Portable units keep the whole compressor indoors, which some find slightly louder in the room itself than a window unit with the compressor mounted outside. Weigh that against the installation flexibility a portable unit offers.
What we would not do
Default to a window unit assuming it’s simply “the proper way” to install air conditioning. For most European homes and window formats, a well-installed portable unit is the more realistic and less complicated choice.
The questions that keep coming up
Is a window unit more efficient than a portable one?
Window units are often considered more efficient in principle since the whole compressor sits outside, but the practical question for most European buyers is installation fit, not efficiency — see our window air conditioner buying guide for the electrical and window-format caveats specific to this format.
Last reviewed 24 August 2026