Baseline sizing by room area
Up to 20m² (bedroom, study): 2.0–2.6kW. Up to 30m² (large bedroom, small living room): 3.2–3.5kW. Up to 45m² (typical living area): 5.0kW. Up to 60m²: 6.0–7.1kW. Open-plan living, kitchen and dining combined: 8.0kW or ducted.
Measure length by width in metres for the area. If the space opens into a hallway or another room without a door, count part of that space too — air goes where it wants, not where the plan says.
What pushes the size up
Large west or north-facing glass, which most Bellarine homes with a view have. Raked or 2.7m-plus ceilings. Little or no ceiling insulation. A dark roof with no sarking. Sliding doors that stay open.
Any two of those and we go up a step. Undersizing to save a few hundred dollars is the most common regret we get called out to fix.
What lets you go smaller
Well-insulated newer builds, double glazing, southern aspect, external blinds or eaves, and rooms you only use at night. A bedroom used for sleeping rarely needs more than 2.6kW.
Multi-head or single?
One outdoor unit running two to four heads keeps the exterior tidy and suits homes where wall space or aesthetics matter — common in Barwon Heads and Newtown. But if one head fails, or the outdoor unit does, everything is offline, and total capacity is shared.
Separate single systems cost more in outdoor units but are more reliable, more efficient per room and cheaper to repair. If the outdoor space allows it, we usually recommend singles.
Anything involving gas, refrigerant or the inside of the unit is licensed work. If you smell gas, shut the gas off at the meter and call the gas emergency line first.
Send us the room dimensions and which way the windows face and we'll tell you the size — no charge, and no upsell to a bigger unit than the room needs.
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