How to Choose the Right Size Air Conditioner for Your Room
Choosing the wrong size air conditioner is one of the most expensive mistakes you can make. A unit that's too small will run constantly without cooling properly. A unit that's too large will cool too fast, cycle off before removing humidity, and cost more to buy and run. Getting the size right matters.
The Basics: Kilowatts and Capacity
Air conditioner capacity is measured in kilowatts (kW) in Australia. The higher the kW, the more powerful the unit. Common residential sizes are: 2.5kW, 3.5kW, 5kW, 6kW, 7kW and 8kW. Larger homes may use multi-split or ducted systems.
Room Size Guidelines
These are general guidelines for a standard ceiling height (2.4m) in a typical Sydney home:
- Up to 20m² (small bedroom, study): 2.5kW
- 20–30m² (medium bedroom, dining room): 3.5kW
- 30–45m² (large bedroom, medium living room): 5kW
- 45–60m² (large living room, open-plan area): 6–7kW
- 60–80m² (large open-plan, combined kitchen/dining/living): 7–8kW
Factors That Increase the Size You Need
- Western Sydney location: Add 10–15% to the guideline capacity. Western Sydney is 3–5°C hotter than coastal areas on summer days.
- North or west-facing rooms: These receive more direct sun and need more cooling power.
- Large windows or glass doors: Sun through glass adds significant heat load.
- Poor insulation: Older homes with no ceiling insulation or single-glazed windows require more capacity.
- High ceilings: Rooms over 2.7m high need larger capacity. Multiply room area by ceiling height divided by 2.4 to find effective volume factor.
What Happens If You Get It Wrong?
Too small: The unit runs at full capacity all day, wears out faster, never fully cools the room, and uses more energy than a correctly-sized larger unit. Too large: The unit short-cycles — it cools the air temperature quickly but doesn't run long enough to remove humidity. The room feels cold but damp and clammy. It also costs more to buy and wastes energy.
Split System vs Ducted
For single rooms, a split system is almost always the right choice. For whole-house cooling of 4+ rooms, ducted is worth considering. Ducted systems are more expensive ($5,000–15,000 installed) but allow you to cool multiple zones from one unit.
Get Expert Advice
Not sure what size you need? Call Oceania Appliances at 0481 243 211. Tell us your room dimensions and location and we'll recommend the right capacity. We supply and install Mitsubishi Electric, Daikin, Panasonic and Fujitsu across greater Sydney. Supply and install from $499.
Showroom: 2/14 Centre Place, Wetherill Park NSW 2164. Open 7 days, 10am–8pm.