What kW does this room need?
A 20 m² bedroom with a 2.4 m ceiling and double glazing needs ≈2.0 kW (Daikin UK rule of thumb, estimate, checked 25 Sep 2026). If the windows face south or west, use the midpoint of Daikin’s 10–20% band, which takes the same room to ≈2.3 kW.
estimate
The formula, from Daikin UK
Daikin UK states that typical UK homes need around 0.1 kW per square metre at average ceiling height, and that a 3 m ceiling (25% more volume) needs 25% more capacity.
South- or west-facing windows are a 10–20% increase. This tool uses the midpoint, ×1.15, and shows it as an estimate.
Single glazing uses ×1.25, the ratio of Daikin’s two 20 m² examples (≈2.5 kW poorly insulated and sun-facing, against ≈2 kW double-glazed). A room under the roof uses ×1.20, the top of that same 10–20% band, because Daikin publishes no separate loft coefficient. Factors are not stacked: the largest one applies.
| Input | Factor | Where Daikin says it |
|---|---|---|
| Ceiling height | height ÷ 2.4 | 3 m ceiling is +25% because volume is +25% |
| South or west windows | ×1.15 (band ×1.10 to ×1.20) | 10–20% for large south- or west-facing windows |
| Single glazing | ×1.25 | 20 m² pair: ≈2 kW against ≈2.5 kW |
| Under the roof | ×1.20 | Top of the published 10–20% band; no loft coefficient is printed |
| More than two people | +0.18 kW each extra person | Published add-on, not in the default 20 m² case |
Daikin UK · Air conditioner size guide · checked 25 Sep 2026. As a rule of thumb, typical UK homes require around 0.1 kW per square metre for average ceiling heights and insulation. Source
Published models near 2.0 kW
These are catalogue families with a registered cooling capacity and a SEER, closest to the default room. Hubs at /best/ are not in this build yet.
| Family | kW | SEER | Page |
|---|---|---|---|
| Daikin 2.0 kW | 2.0 | 6.6 | /units/daikin-atx-2kw-arx20k/ |
| Daikin 2.0 kW | 2.0 | 6.1 | /units/daikin-atxf-2kw-arxf20a/ |
| Daikin 2.0 kW | 2.0 | 6.1 | /units/daikin-atxf-2kw-arxf20c/ |
| Daikin 2.0 kW | 2.0 | 6.4 | /units/daikin-atxf-2kw-arxf20d/ |
| Daikin 2.0 kW | 2.0 | 6.4 | /units/daikin-atxf-2kw-arxf20d-1684130/ |
| Daikin 2.0 kW | 2.0 | 6.4 | /units/daikin-atxf-2kw-arxf20e/ |
Next pages
Daikin UK, air conditioner size guide · page checked 25 Sep 2026 · n=1 manufacturer guide · 0.10 kW/m² scaled by height/2.4, then the largest of the published adjustment factors · updated 25 Sep 2026 · version 1.0.0 · CSV of the values on this page
Source detail
https://www.daikin.co.uk/en_gb/residential/inspiration/articles/air-conditioner-size-guide.html