Why Getting the Size Right Matters
Air conditioning capacity is measured in kilowatts (kW). An undersized system runs non-stop and still can’t reach your target temperature. An oversized system short-cycles — it cools quickly, switches off, then the room warms up again. Neither is comfortable, and both waste electricity.
The Basic Rule of Thumb (and Why It’s Not Enough)
You’ll often see a table like this: 0.15 kW per square metre, so a 20m² room needs 3kW. This is a starting point, not an answer. The real calculation accounts for:
- Ceiling height (higher ceilings = more air volume to condition)
- Window area and orientation (north-facing rooms get much more heat load)
- Insulation level (older Sydney homes without ceiling insulation need more capacity)
- Occupancy (a living room with 5 people generates significant heat load)
- External shading (eaves, trees, and neighbouring buildings all reduce heat load)
The Accurate Method: Load Calculation
Our team uses a proper load calculation for every installation. We measure your room, check insulation, assess window area, note orientation, and run the numbers. This adds 30 minutes to your quote visit but gives you a system that’s properly sized for the next 10+ years.
What Happens If You Get It Wrong
An undersized system shows its problems immediately — it can’t reach your set temperature on hot days. An oversized system is more insidious. The room cools quickly, but the system shuts off before it has run long enough to dehumidify the air. The result is a room that feels cold and damp rather than cool and comfortable.
Our Recommendation
Book a free on-site assessment. We’ll measure your space, assess your home’s construction, and recommend the right capacity. There’s no obligation to proceed, and you’ll leave with an accurate specification — not a guess.
