For most Sydney homes the answer comes down to three things: how many rooms you actually need to cool, how often the whole house is occupied at once, and whether you’re staying long enough to get the value back out of a ducted install.

Quick version: split systems win on upfront cost and suit smaller homes or rentals. Ducted wins on whole-home comfort, resale value, and looks, and starts paying off in family homes that run aircon hard for half the year. The detail is below, including real costs and the situations where the obvious answer turns out to be wrong.

How each system actually works

A split system is a single indoor head unit mounted on a wall, paired with a single outdoor condenser. The two are connected by refrigerant lines and a power cable. Each system cools and heats one room or one open-plan area. If you want aircon in three bedrooms, you’ve got three indoor units and three outdoor units (or a multi-split, which is one outdoor unit running multiple indoor heads).

A ducted system is one larger indoor fan coil unit hidden in the roof cavity, paired with one outdoor condenser. Insulated ducts run through the roof space and out through slim vents in every room you want covered. One thermostat. One system. Whole house.

Cost: upfront, running, and over ten years

This is where most online comparisons go vague. Real numbers across Sydney installs in 2026:

Upfront, supplied and installed:

A single 7.1kW split system in a standard Sydney home: $2,200 to $3,500 depending on brand and install complexity. Add roughly the same again per additional room if you’re doing multiple splits.

A ducted system in a four-bedroom Sydney home: $9,000 to $14,000 for a competent mid-range setup with proper zoning. Premium brands and complex two-storey installs push higher, $15,000 to $20,000 isn’t unusual for a five or six-bedroom home in places like Castle Hill or Bella Vista.

Running costs (Sydney, summer, average use):

A 7.1kW split system cooling a living area for 6 hours a day costs roughly $2 to $4 per day to run on current Sydney electricity rates.

A ducted system running across a four-bedroom home for similar hours, with proper zoning, costs $5 to $9 per day. Without zoning, or with the system trying to cool the whole house when only one zone is used, that figure can double.

Servicing:

Both need annual professional service. A split is $150 to $250. A ducted system is $250 to $400.

Over ten years:

Three split systems for a four-bedroom home: roughly $7,500 upfront plus $4,500 servicing, plus running costs.

A ducted system: roughly $11,000 upfront plus $3,500 servicing, plus running costs.

The ducted system isn’t dramatically more expensive over its life, but it does need more cash upfront. That’s the genuine financial trade-off, not a vague “ducted costs more”.

Where each system genuinely wins

Split systems make more sense if:

You’re cooling one or two rooms, not the whole house. Spending $11,000 on ducted to mostly use the living room is poor value.

You’re in an apartment or a townhouse where ducting through the ceiling isn’t possible. Body corporate rules in inner-west and eastern suburbs apartments often restrict ducted installs anyway.

You’re renting out the property and want simple, replaceable units. A failed split is a one-room problem. A failed ducted system is the whole house.

You’re staying short-term. Ducted’s resale value benefit doesn’t apply if you’re moving within three years.

You’ve got an older home where running ducts through the ceiling cavity is structurally difficult. We see this in Federation homes and worker’s cottages around the inner west, where the roof space won’t accommodate proper duct runs.

Ducted makes more sense if:

You’re in a four-plus bedroom home and the whole family is home most evenings. The cost-per-room maths starts working in ducted’s favour around the four-bedroom mark.

You want consistent temperatures across the house. Walking from a 22°C living room into a 28°C bedroom is the most common complaint we hear from owners of multi-split setups.

The home has high ceilings, open-plan living, or multiple stories. Splits struggle to throw air across large open spaces, ducted distributes evenly.

Aesthetics matter to you. Slim ceiling vents are far less visually intrusive than wall-mounted heads in every room.

You’re staying long enough to get the resale benefit. In family-home suburbs across Sydney (Castle Hill, Cherrybrook, Kellyville, the Hills district generally, plus newer estates in Oran Park, Leppington and Edmondson Park), ducted is now the buyer expectation, not the bonus. A home without ducted at that price point gets marked down.

Where the obvious answer is wrong

A few situations come up often where the quick answer leads people astray.

The “I’ll just add a split system per room” plan. This sounds cheaper than ducted and looks cheaper on paper. Once you’re past three rooms, the cost gap closes fast, you’ve got multiple outdoor units cluttering the side of the house, and the inconsistent temperatures between rooms become the new complaint. Three or more splits is the point where ducted usually starts winning on both cost and outcome.

The “ducted is energy-hungry” assumption. This was true twenty years ago. Modern inverter-driven ducted systems with proper zoning are competitive on running costs with multi-split setups. The homes where ducted runs expensively are the ones with no zoning, oversized systems, or systems being run as if they’re a single split (cooling the whole house to handle one room).

The “I’ll get a small ducted to save money” idea. An undersized ducted system runs flat out on hot days, never quite hits the set temperature, wears its components faster, and ends up costing more in repairs and power than a properly sized one. Sizing is calculated against floor area, ceiling height, insulation, window orientation and zoning. Anyone quoting a system without doing this calculation isn’t doing the job properly.

Zoning is what makes modern ducted work

If you take one thing from this article, take this. A ducted system without proper zoning is a system that cools and heats the whole house every time it runs. That’s where the “ducted is expensive” reputation comes from.

A zoned ducted system splits the house into separately controlled areas (typically four to six zones in a Sydney family home). Each zone can be turned on or off, and on better systems, each can run at slightly different temperatures.

Used properly, you’re only conditioning the rooms you’re actually in. On a 38°C Saturday afternoon when only the living area is occupied, you’re running maybe 30% of the system’s capacity, not 100%. That’s where the running cost gap with a multi-split closes.

Zoning controllers worth knowing about: MyAir 5, AirTouch 5, ActronAir Que and Daikin’s Zone Controller. Any of these will give you proper individual room control.

What we’d actually recommend

For a typical Sydney three-bedroom apartment or small house with one open living area: one or two splits, sized properly. Done.

For a typical Sydney four or five-bedroom family home where everyone’s home in the evenings: zoned ducted, with the zoning designed around how the family actually uses the house, not just one zone per room.

For an older or heritage home where ducting is structurally difficult: multi-split, with thought put into outdoor unit placement so you don’t end up with three condensers stacked on the side wall.

For a renovation or new build: ducted is almost always the right call, because the install cost is dramatically lower when you’re doing it before plaster goes up.

Frequently asked questions

How long does each system last? A well-maintained split system: 10 to 15 years. A well-maintained ducted system: 15 to 20 years. Both figures drop sharply without regular servicing.

Can I run one system to cool and another to heat? Both ducted and split systems available in Australia today are reverse-cycle, meaning they handle both heating and cooling. You don’t need separate systems.

How long does installation take? A standard single split system: half a day. Multi-split: one day. Ducted in an existing home: 1 to 2 days, sometimes 3 for complex two-storey jobs. Ducted in a new build is faster because it goes in before plaster.

Do I need approval to install ducted? For most freestanding homes, no. Apartments and townhouses usually require body corporate approval. Heritage-listed properties in places like Glebe, Paddington and parts of the inner west may need additional consent for outdoor unit placement.