Once a Brisbane household wants aircon in more than one or two rooms, the same question comes up: do you run several single-room split systems, install one multi-head system, or go ducted? Multi-head split systems sit in the middle, and they’re often the most cost-effective option for homes that don’t suit full ducting but need more than a single room cooled. Here’s how they actually work.
How a multi-head system works
A multi-head (or “multi-split”) system uses a single outdoor condenser unit connected to two or more indoor units, each in a different room. One inverter compressor modulates output across all the connected heads, so each room can be run independently – on, off, or at a different temperature – without needing a separate outdoor unit for every room. This is different from simply installing several single-room split systems side by side, which each need their own dedicated outdoor unit and circuit.
How many indoor units can one outdoor unit run?
Most residential multi-head systems from major brands support anywhere from 2 to 5 indoor heads on one outdoor unit, depending on the model range. The real constraint isn’t the number of heads, it’s the combined capacity: manufacturers publish a maximum combined indoor kW rating for each outdoor unit, and if you add up the capacity of every indoor head you want, it needs to sit within that limit. In practice, this means a larger outdoor unit is needed to run five small rooms than to run two large ones, and we size the outdoor unit off the total combined load, not just a head count.
Multi-head vs. individual splits vs. ducted
- Multi-head split – one outdoor unit, cleaner outdoor footprint, one dedicated circuit, each room controlled independently. The trade-off: if the single outdoor unit needs repair, every connected room can lose cooling at once, and running every head hard at the same time draws on shared compressor capacity.
- Individual single splits – more outdoor units and switchboard circuits, but each room is fully independent of the others if one system needs service.
- Ducted – the best result for whole-home comfort and the cleanest look internally, but a significantly bigger investment and it needs ceiling space for ductwork, which not every Brisbane home – especially older Queenslanders on stumps with limited roof cavity – can accommodate without compromise. See our guide to split system vs ducted air conditioning for the full comparison.
As a rough guide in the Brisbane market, a 2-head multi-split covering two bedrooms typically starts from around $5,500-$7,500 installed, while a 4-5 head system across a full living/bedroom footprint can run from $11,000-$16,000+ depending on capacity, brand and install access. Ducted systems for an equivalent home are usually a meaningful step above that. We always quote off the actual rooms, orientation and roof access rather than a rule of thumb.
Sizing for Brisbane’s climate
Correct sizing matters more in a multi-head system because an undersized outdoor unit struggles the moment two or three rooms call for cooling at once on a 35-degree Brisbane afternoon. Sizing needs to account for room orientation, roof insulation, window size and glazing, and whether north or west-facing rooms are in the mix – see our guide on what size air conditioner you need for the basics. Undersizing to save money on the outdoor unit is the most common mistake we see corrected on multi-head jobs.
Installation and compliance
Multi-head systems need a refrigeration licence for the refrigerant work and ARCtick certification, plus a licensed electrician for the dedicated circuit back to the switchboard, in line with AS/NZS 3000. Outdoor unit placement also needs to meet Brisbane City Council noise and boundary setback requirements, particularly in townhouse and duplex settings where the condenser sits close to a neighbour’s fence line.
Is multi-head the right fit for your home?
Multi-head systems tend to suit homes cooling 2-4 rooms where full ducting isn’t practical or isn’t justified by the budget, and where you want each room controlled separately rather than one whole-house zone. If you’re planning to eventually cool most of the house, it’s worth pricing ducted alongside a multi-head quote before committing, since the outdoor unit and installation labour are where the two options genuinely diverge in cost.
Not sure which setup suits your home? See our air conditioning services or get in touch for a free on-site quote.
Related guides
- Split system vs. ducted air conditioning: which is right for you?
- What size air conditioner do I need?
- How ducted air conditioning zoning works in Brisbane homes
Need a licensed Brisbane electrician? See our electrical services or get in touch for a quote.