Where 9 kW appears
Two guides mention it, both as a ceiling rather than a target. The CHOICE table that Solar Victoria reproduces gives rooms over 80 square metres a range of 6 to 9 kW. Rinnai's buyers guide gives extra large rooms, 60 square metres and up, 7.0 to 9.0 kW.
The ACT Government's guide says larger split systems can service areas of up to 80 square metres. For a very large room, its answer is a small multi-head system rather than a bigger split.
Why a space can seem to need 10 kW
Rules of thumb grow quickly on big areas. ActronAir's own example multiplies 100 square metres by 150 watts to get 15 kW, and warns the method misses many important factors.
Some of those factors can be fixed. ActronAir says a well insulated home likely won't need as much capacity, and CHOICE says a split in a well-insulated, well-sealed house can hold a comfortable temperature at very low power. Before buying the biggest unit, ask whether insulation, blinds or closing off a stairwell would shrink the job.
In Victoria, 10 kW changes the VEU co-payment
VEU (Victorian Energy Upgrades) discounts on reverse cycle heating and cooling come from accredited providers, and the program is voluntary. Under the current rules, the minimum co-payment for a single split of 10 kW or above is higher than for one below 10 kW.
If a unit sits close to that line, ask the provider which side of it the model falls, and whether your job could qualify at all. Our VEU guide explains how the discounts work.
Before you agree to a 9 or 10 kW split
- A heat load in writing, not just a floor area.
- A straight answer on why two smaller units or a multi-head wouldn't suit the space better.
- An outdoor spot with open air around it and room to service the unit.
- If VEU is involved, the accredited provider's name and the co-payment that applies.
- An RTA number, starting with AU, printed on the quote itself.
Your homework, and the installer's
You can
- Put the space through the size calculator, then look honestly at what makes it hard to heat or cool: glass, height, gaps.
- List the rooms you actually use, and when.
Leave to a licensed installer
- A proper heat load, and an honest view on whether a single split is the answer.
- Planning a multi-head or ducted alternative. A multi-head needs a full RAC01 licence holder.
- The electrical and refrigerant work.
What we'd do
Our take
If someone suggests a 9 or 10 kW split for one space, we'd ask to see the heat load, then ask what two smaller units or a multi-head would look like. If the house is over 180 square metres and you'd like most rooms comfortable, we'd have a ducted specialist look too, because the ACT guide points larger homes that way. One big split for one big room is fine, if the numbers back it.
