What Size Air Conditioner Do I Need? — Room-by-Room Guide
Choosing the wrong size air conditioner is one of the most common mistakes when buying a split system. Too small and it runs constantly without reaching temperature; too large and it short-cycles, failing to dehumidify the room properly. Here's how to get it right.
How Air Conditioner Capacity Is Measured
Air conditioner capacity is measured in kilowatts (kW). The kW figure on a split system refers to its cooling capacity. Most residential units range from 2 kW (small bedroom) to 9 kW+ (large open-plan space).
Basic Rule: 0.1 kW Per Square Metre
As a starting point, allow approximately 0.1 kW per square metre of floor space. For a 20 m² bedroom, that's 2 kW. For a 40 m² living area, that's 4 kW.
Important: this is a starting point, not the final answer. You need to adjust for:
- Ceiling height — rooms with 3m or higher ceilings need more capacity
- Direct sun — rooms facing west or north in Sydney get much hotter; add 15–25%
- Insulation — poorly insulated homes or older weatherboard houses need extra capacity
- Number of occupants — each person generates heat
- Number of windows and their size — large unshaded windows dramatically increase load
Room-by-Room Guide for Sydney Homes
| Room Type | Typical Size | Recommended kW |
|---|---|---|
| Small bedroom | 12–15 m² | 2.0–2.5 kW |
| Medium bedroom | 15–20 m² | 2.5–3.5 kW |
| Large bedroom / master | 20–30 m² | 3.5–5.0 kW |
| Open-plan living/dining (small) | 30–45 m² | 5.0–6.0 kW |
| Open-plan living/dining (large) | 45–60 m² | 6.0–8.0 kW |
| Large open plan / entertaining | 60+ m² | 8.0 kW+ |
Sydney Climate Adjustment
Sydney's summer heat is intense, especially in the west (Penrith, Liverpool, Campbelltown, Blacktown). For homes in these areas, go to the higher end of the range or even one size up from the chart. Reverse-cycle units are ideal for year-round use — the same unit that cools in summer heats in winter.
Get Expert Advice
Not sure what size you need? Call us at Oceania Appliances and describe your room. We'll help you choose the right capacity from our range of Daikin, Mitsubishi Electric, Fujitsu and other premium brands. Free delivery across Sydney, 3–6 month warranty on every unit.
Call: 0450 220 436 | Shop: oceaniaappliances.com.au