Is ducted air conditioning better than split systems?

Neither is better in general. Ducted suits a house where you want even, invisible conditioning across most rooms and have the roof space for it. Splits suit a house that needs two or three rooms comfortable, has no usable roof cavity or wants to add rooms gradually. Plenty of Australian homes end up with some of each.

Do you need roof space for ducted air conditioning?

Yes. The indoor fan coil sits in the roof cavity with the ductwork running out to every outlet, so you need both height and access. A low-pitch roof, a concrete slab ceiling, an apartment or an extension under a skillion roof often will not take it. Sometimes a bulkhead or an under-floor route solves it, which is a site-visit conversation.

Is ducted air conditioning more expensive to run than split systems?

It depends on how you use it. Conditioning a whole house costs more than conditioning one room, so a ducted system running every zone costs more than a single split. A zoned ducted system cooling two bedrooms overnight does much the same work as two splits. Zoning decides it more than the technology.

How many split systems can I run off one outdoor unit?

A multi-head system typically runs two to five indoor heads off one outdoor unit, which saves wall space and looks tidier than a row of condensers. The heads share one compressor, so on most multi-head systems one room cannot heat while another cools. Separate single-head systems keep that flexibility.

Air conditioning

Ducted or split system: which one suits your house?

What your house physically allows rules out ducted or splits more often than budget does. Start with the roof space, then think about how many rooms you really live in and when.

2 October 20266 min read

The short version

Ducted suits you if you want most of the house comfortable with nothing on the walls and your roof has space to run it. Splits suit you if two or three rooms are enough, your roof will not take ductwork or you want to add rooms over time. Check the roof first.

What each one is

A split system is two boxes: an indoor head on the wall of the room you want conditioned and an outdoor condenser outside, joined by a pair of insulated copper lines. One head conditions one space. Each extra room needs another head, either with its own outdoor unit or sharing a multi-head condenser.

A ducted system hides one larger indoor unit in the roof cavity and sends conditioned air through insulated ductwork to outlets in each room. You see ceiling vents, a return air grille somewhere central and a controller on the wall. Zones let you switch groups of rooms on and off.

Almost every current installation of either type is reverse cycle, so both heat as well as cool. The difference is how the air gets to you.

Side by side

The differences that change the decision.

	Ducted	Split system
What you see	Ceiling vents and a wall controller.	A head on the wall in every conditioned room. Each needs a condenser outside unless they share a multi-head unit.
What the house needs	A roof cavity with height and access for the unit and duct runs.	An external wall near each room and a spot for the condenser.
Coverage	The whole house or whatever the zoning covers.	Room by room. Anything without a head stays as it was.
Control	A central controller with zones. Basic zoning runs every zone off one setpoint. Many systems offer separate temperature control per zone as an option.	Each room set independently. Separate systems can even heat one room while another cools.
Adding capacity later	Difficult, because installation fixes the unit size and the duct runs.	Straightforward. Add another head whenever you want.
Installation disruption	Substantial. Ceiling access, duct runs and cutting outlets make it a multi-day job.	Modest. Often a day or less per head with one core hole through the wall.
Running it	Efficient across a whole house but wasteful if you run every zone to cool one room.	Efficient for one or two rooms. It gets expensive as heads multiply.
Resale	Buyers tend to see it as a whole-house feature.	Reads as fitted appliances. Nice to have but less of a selling point.

Start with the roof, not the budget

There is no point weighing up zoning for a house that cannot take ductwork, so check that first.

A ducted system needs somewhere for the indoor unit to sit and a path for insulated duct to reach every outlet. That usually means a pitched roof with reasonable height at the ridge and room to move around. Apartments, concrete ceiling slabs, low-pitch and skillion roofs and single-storey extensions whose roof does not connect to the old cavity commonly fail this test.

Then there are the outlets. Getting duct to a room means getting it above that room. A dropped ceiling, a bulkhead in the wrong place or a cathedral ceiling with no cavity above it all complicate that. Sometimes a bulkhead or an under-floor route solves it. Sometimes nothing does and that room stays unducted.

We settle it by getting up into the roof and looking, which takes about half an hour and saves a lot of theorising.

Then think about how you actually use the house

The second question is how many rooms you really want conditioned and when. For most households that is fewer rooms than the house has.

A household that lives in the kitchen and lounge, sleeps in one bedroom and uses the others twice a year is a split system household, even in a big house. Two well-placed heads do everything that matters. Ducted in that house means paying to send air to rooms nobody sits in.

A household where people work from different rooms, the kids go to bed before the adults or the upstairs is unbearable by four in the afternoon is a ducted household. The zoning is the point.

Plenty of houses end up with both: ducted through the living areas and bedrooms with a split in the granny flat, the garage workshop or the one room the ductwork could never reach.

What drives the cost

We do not publish a price comparison, because the same system in two houses can be two very different jobs.

On a ducted job the cost moves with roof access and how tight the cavity is, the number of outlets and zones, how far the duct has to run, the ceiling material and whether the switchboard can carry the load. On splits it moves with the distance between head and condenser, how straight the pipe run is, how high the outdoor unit sits and again the switchboard.

Two things hold regardless. Ducted is the bigger job upfront and hard to extend later, so the sizing and zoning have to be right the first time. Splits let you spread the work out, but every head added later is its own install. Four splits also means four sets of filters to clean instead of one.

A site visit and a fixed price give you the real number. That is how we quote every job. Check the NSW Government rebate before you commit either way. Standby is an NSW Government rebate installer and an eligible upgrade attracts a government discount on the job.

One thing people get wrong on both

Sizing. Too big a system reaches the set temperature in minutes and switches off while the air is still damp, so the room feels chilled but sticky. It applies to a single head and a whole ducted design alike. What size air conditioner do I need goes through how to work out the number and what moves it.

Common questions

Is ducted air conditioning better than split systems?: Neither is better in general. Ducted suits a house where you want even, invisible conditioning across most rooms and have the roof space for it. Splits suit a house that needs two or three rooms comfortable, has no usable roof cavity or wants to add rooms gradually. Plenty of Australian homes end up with some of each.
Do you need roof space for ducted air conditioning?: Yes. The indoor fan coil sits in the roof cavity with the ductwork running out to every outlet, so you need both height and access. A low-pitch roof, a concrete slab ceiling, an apartment or an extension under a skillion roof often will not take it. Sometimes a bulkhead or an under-floor route solves it, which is a site-visit conversation.
Is ducted air conditioning more expensive to run than split systems?: It depends on how you use it. Conditioning a whole house costs more than conditioning one room, so a ducted system running every zone costs more than a single split. A zoned ducted system cooling two bedrooms overnight does much the same work as two splits. Zoning decides it more than the technology.
How many split systems can I run off one outdoor unit?: A multi-head system typically runs two to five indoor heads off one outdoor unit, which saves wall space and looks tidier than a row of condensers. The heads share one compressor, so on most multi-head systems one room cannot heat while another cools. Separate single-head systems keep that flexibility.