What Size Air Conditioner Do I Need? A Room-by-Room Guide for Sydney Homes
Choosing the wrong size air conditioner is one of the most common mistakes Australian homeowners make. Buy one too small and it will run constantly without reaching your temperature target. Buy one too large and it will cycle on and off frequently, wasting energy and failing to dehumidify properly. Here's how to get it right.
How Air Conditioner Size Is Measured
Air conditioner capacity is measured in kilowatts (kW). This refers to the heating or cooling output — not the power consumption. A 3.5kW unit can deliver 3.5kW of cooling output, typically while consuming around 1kW of electricity (thanks to inverter technology).
The Basic Sizing Guide
The standard starting point for sizing an air conditioner is based on floor area. Use these as a rough guide for well-insulated rooms with standard ceiling heights:
- Up to 20m² (small bedroom, study) — 2.5kW
- 20–30m² (main bedroom, mid-sized living room) — 2.5–3.5kW
- 30–45m² (open plan dining/kitchen, large bedroom) — 3.5–5.0kW
- 45–60m² (large open plan area) — 5.0–6.0kW
- 60–80m² (large combined living area) — 6.0–8.0kW
- 80m²+ (very large open plan) — 8kW+
Factors That Affect the Right Size
Floor area is just the starting point. These factors can mean you need to size up:
- Poor insulation or older home: Size up by 20–25%
- Large windows or north-facing rooms: More sun means more heat load
- High ceilings (over 2.7m): More air volume to condition
- Open plan to adjacent areas: Account for connected spaces
- Sydney climate: Hot humid summers mean you should err on the side of slightly larger
- Dark coloured roof: Increases heat load in summer
Room-Specific Recommendations for Sydney
Main bedroom (12–16m²): 2.5kW is usually sufficient for a standard bedroom.
Main bedroom with ensuite/walk-in (16–20m²): 2.5–3.5kW depending on layout.
Living/dining combo (40–60m²): 5–6kW is typical for a standard Sydney home.
Open plan kitchen/living/dining (60m²+): 7–8kW+ — consider a ducted system for even distribution.
Split System vs Ducted
For single rooms, a split system is the most cost-effective solution. For whole-home climate control, a ducted system provides even airflow throughout. Ducted systems are sized for the total conditioned area of the home.
Need help choosing the right air conditioner for your Sydney home? Contact Oceania Appliances — we can help you select the correct capacity. Free delivery across Sydney.