Air conditioners · 5 min read
Air conditioners: how many BTU for your room
The right capacity for your square metres, what the BTU in the name mean, portable or single split, SEER and EER, and when you need an F-gas technician.
In this guide
Capacity by room size
With ceilings around 2.7 m and average insulation, the rule of thumb is:
| Room | Capacity |
|---|---|
| up to 20 m² | 7,000–8,000 BTU/h (≈ 2–2.3 kW) |
| 20–25 m² | 9,000 BTU/h (≈ 2.6 kW) |
| 25–35 m² | 10,000–12,000 BTU/h (≈ 2.9–3.5 kW) |
| 35–50 m² | 18,000 BTU/h (≈ 5.3 kW) |
Very sunny rooms, top floors or large glazing need the next size up.
Air conditioners up to 9,000 BTU · 10,000 to 12,000 BTU
The BTU in the product name
The name of every air conditioner gives its nominal cooling capacity, rounded to the nearest size. 1 kW is about 3,400 BTU/h, so a 2.4 kW model (8,200 BTU/h) is an 8,000 BTU unit and a 2.6 kW one (8,900 BTU/h) a 9,000 BTU unit. Some brands advertise the maximum capacity, which is higher: in the specifications you find it as “Peak cooling capacity”. To compare two models, use the nominal capacity.
Portable or single split?
A portable unit is a single body on wheels: no outdoor unit and no technician, you plug it in and run the hot-air hose out of a window or French window. It suits a rented room or a few weeks of use a year. At the same BTU it cools less than a split, because the air it blows out is replaced by warm air coming in from outside: if the room is at the top of a band, choose the next size up.
A single split has a wall-mounted indoor unit and an outdoor unit, joined by copper pipes. It has to be installed by a technician, but to cool all summer it uses less energy and is quieter; with its heat pump it also heats in spring and autumn. The single splits on Oblò are complete kits with indoor and outdoor unit.
See the portable air conditioners · See the single splits
SEER, SCOP, EER and COP
For split units the energy label gives the seasonal efficiency in cooling (SEER) and heating (SCOP): SEER above 6 and SCOP above 4 mean an efficient unit. For portables you read the EER (cooling) and, on models that heat, the COP: these are lower than SEER and SCOP and are not comparable with them.
Installing a split unit
Split air conditioners contain a fluorinated gas (R32 in our models) and the circuit is closed when the unit is fitted: by law they must be installed by an F-gas certified company, and the sale needs a declaration of who will install them (Reg. (EU) 2024/573, DPR 146/2018). Oblò sells single splits only together with its own certified installation, which we add to the order at a fixed price, 249,00 €: up to 3 m of piping, one wall hole, brackets and start-up. Extra work (chasing, longer pipes, high-level brackets) is quoted beforehand.
Portable units are sealed at the factory and need no installation: they come by express courier.
We take your old fixed air conditioner away for free once it has been removed; removal with gas recovery by an F-gas technician is quoted when the new split is installed.
