Wall, floor console, cassette or ducted: choosing the indoor unit

Updated September 3, 2026 · Claude AC · 2 sources cited

Contents (7)

Five formats, and what each asks of the building
Why the high wall unit deserves its default status
The floor console, Europe's under-used answer
Cassettes and ducted units: what the ceiling has to give
Mixing formats on one outdoor unit
Choose by the room, not by the catalogue
Frequently asked questions

Almost every European buying air conditioning chooses the outdoor unit carefully — brand, capacity, efficiency class, sound power — and then accepts whatever indoor unit the installer proposes, which is the high wall model in nine cases out of ten. That is the wrong way round. The outdoor unit decides the electricity bill; the indoor unit decides whether you like living with the machine: where the air lands, how the room heats in February, how much of the ceiling has to be sacrificed, and whether the job is even possible in a flat built in 1890.

Five formats, and what each asks of the building

The same outdoor unit and the same refrigerant can serve very different indoor formats. What separates them is not performance but geometry — where the unit fits, where the condensate goes, and where the air is thrown.

Format	What the building must offer	Condensate	In heating mode	Indicative relative cost
High wall	Clear wall near the ceiling, close to the outdoor unit	Usually gravity, straight through the wall	Fine, but delivers warm air above head height	The reference — the cheapest option
Floor console	Free wall at floor level, typically under a window	Gravity if the ground allows, otherwise a small pump	Best of the formats: warm air at floor level	Roughly a fifth to a half more than a wall unit
Ceiling cassette	A suspended ceiling with a clear void, commonly 25–35 cm depending on the model	Nearly always a condensate pump	Good, but four-way throw can feel draughty	Well above a wall unit, plus ceiling work
Ducted	A ceiling, floor or loft void for the unit and the ductwork	Pump, plus an accessible drain route	Even, discreet, quiet if properly designed	The most expensive route by a wide margin
Wall monobloc (no outdoor unit)	An external wall, two core-drilled holes	Gravity or evaporative, model dependent	Limited — modest output in cold weather	Comparable to a wall split, less capacity

Those cost positions are relative, not prices: the equipment is only half the job in Europe, and the labour half varies by a factor of several between member states. Our guide to installation costs across Europe breaks the two apart.

Why the high wall unit deserves its default status

It is the format the entire industry optimises. The widest model range, the highest seasonal efficiencies on the datasheets, the quietest declared figures — manufacturers claim sound pressure down to around 19 to 21 dB(A) at minimum fan speed on their flagship wall units, a level no cassette or ducted unit reaches, because those formats push air through longer paths. It is also the fastest to install, and the only one that normally drains by gravity, which removes a pump and its noise from the equation.

Its weaknesses are equally structural. It sits high, so in cooling it works with physics — cold air falls — and in heating it works against it, throwing warm air across the ceiling of a room whose floor stays cool. It needs a genuinely free stretch of wall near the ceiling, which rules out rooms with cornices, high picture rails or a beam where the pipe run wants to go. And it is visible: in an apartment with mouldings, it is the format people regret aesthetically.

The floor console, Europe's under-used answer

The console is a low, radiator-shaped indoor unit fitted at skirting level, usually under a window. It is common in Japan and in Nordic heat pump installations and strangely rare in southern Europe, where it often makes more sense than the wall unit that gets chosen instead.

Two arguments carry it. The first is heating: if you intend to use the machine as your main heat source through the winter — increasingly the point of buying one at all, as our guide on heating with an air conditioner explains — delivering warm air at floor level heats the occupied part of the room instead of the ceiling. The second is retrofit geometry: a console occupies the space a radiator already had, which is often exactly where the old heating pipes and an outside wall coincide. Many models blow from two outlets, low and mid-height, which suits both seasons.

Against it: a footprint that constrains furniture, more exposure to knocks and vacuum cleaners, a smaller catalogue than wall units, and drainage that frequently requires a small pump because there is no downward run available at floor level. Pumps are reliable, but they hum, and a hum at floor level in a bedroom is not the same as a hum at ceiling level.

Cassettes and ducted units: what the ceiling has to give

Both formats disappear into the building, which is why architects like them and why they defeat most European retrofits. A four-way cassette needs a suspended ceiling with a clear void — commonly in the region of 25 to 35 cm depending on the chassis, plus room for the drain pump and its rising pipe. That void exists in offices, new builds and villa renovations. It does not exist in a Haussmann apartment with a 3.2 m plaster ceiling and mouldings you are not allowed to touch, and lowering such a ceiling is a project of its own.

Ducted units are the same logic taken further: the machine hides in a void or a loft and delivers through grilles, giving the most discreet result and the most even temperature distribution. The trade-off is that comfort depends on the duct design rather than the box — undersized or uninsulated ducts waste capacity and generate noise no brand name will save you from — and that it is a renovation-time decision. Retrofitting ducts into a finished apartment is rarely worth what it costs.

One practical point buyers forget on both: filter access. A cassette filter is cleaned from below through the grille, which is manageable; ducted filters can end up behind a hatch nobody wants to open, and a filter nobody cleans quietly destroys the performance the system was bought for.

Mixing formats on one outdoor unit

Indoor formats can be mixed on a single multi-split outdoor unit — a console in the living room, wall units in the bedrooms, a cassette in a low-ceilinged extension — within the manufacturer's combination and capacity-ratio rules. Two limits apply. All indoor units share one refrigerant circuit, so they cool or heat together and cannot run opposite modes, and each added indoor unit shortens the capacity available to the others when everything runs at once. The full arithmetic is in our guide to multi-split systems.

Choose by the room, not by the catalogue

Bedroom: the quietest wall unit you can afford, mounted so the airflow does not cross the bed. Draught over a sleeping body is the top complaint in European bedrooms, ahead of noise.
Living room used for winter heating: a console under the window, or a wall unit only if the room is well insulated and the ceiling is low.
Open-plan space with a false ceiling: a cassette, positioned away from the dining table and the desk.
Whole-flat project during a renovation: ducted, decided before the ceilings go up, never after.
Listed façade or a co-ownership that refuses an outdoor unit: a wall monobloc, with the compromises set out in our guide to air conditioning without an outdoor unit.

Whichever format you choose, size it for the room rather than for the format — an oversized cassette short-cycles exactly like an oversized wall unit, dehumidifies badly and wears itself out faster. Start from the load, using our method for sizing an air conditioner in kW, then pick the shape that suits the wall, the ceiling and the way you will actually live in the room.

Frequently asked questions

Which type of indoor unit is the quietest?

The high wall unit, generally by a clear margin: manufacturers' flagship models declare sound pressure around 19 to 21 dB(A) at minimum fan speed, while cassettes and ducted units move air through longer paths and rarely go that low. Always compare the declared figures in the datasheet at the same fan speed, and remember that a condensate pump adds a noise the specification does not include.

Can I install a ceiling cassette in a flat without a false ceiling?

Not without building one. A cassette chassis needs a clear void, commonly 25 to 35 cm depending on the model, plus space for its drain pump. In an apartment with a decorated plaster ceiling, the realistic options are a wall unit, a console or, during a full renovation, a ducted system.

Is a floor console really better for heating?

For the same capacity, yes, in most European rooms. Warm air introduced at floor level mixes through the occupied zone instead of collecting under the ceiling, which is why consoles are standard in Nordic heat pump retrofits. The gain is largest in rooms with high ceilings and modest insulation — exactly the older housing stock much of Europe lives in.

Do all indoor units need a condensate pump?

No. A wall unit mounted high on an external wall usually drains by gravity, which is one reason it costs less to install. Consoles, cassettes and ducted units generally need a pump because the drain has to rise before it can fall. Pumps are cheap and reliable, but they are also a maintenance point and a small source of noise.

Can I put different types of indoor unit on the same outdoor unit?

Yes, on a multi-split, within the manufacturer's authorised combinations and total capacity ratio. The constraint is not the mix of shapes but the shared refrigerant circuit: every indoor unit must be in the same mode, so heating one room while cooling another needs separate systems or commercial heat-recovery equipment.