Split system vs ducted AC in Perth: which is right for your home?

For Perth homes, air conditioning isn't optional: it's essential. The question is which type of system suits your home, budget, and energy goals. Split systems and ducted reverse-cycle air conditioning are the two dominant residential options in Perth, and the right choice depends on your house size, how you use your home, and whether you have (or plan to have) solar.

What's the actual difference

Split system air conditioning consists of one outdoor unit (compressor) connected to one indoor unit (wall-mounted head). Each split system cools a single zone, typically one room or open-plan living area. A home with 3 bedrooms and a main living area might have 3–4 separate split systems, each independently controlled.

Ducted reverse-cycle air conditioning uses one large outdoor unit connected to a ceiling-mounted indoor unit that distributes air through ducts to every room in the house. A single thermostat (or zone controller) manages the whole home from a central panel.

Both systems provide both heating and cooling (reverse-cycle).

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Cost comparison

Installation cost

Split systems:

• Single unit (bedroom, 2.5kW): $1,200–$2,000 installed
• Living area unit (7.0–8.0kW): $2,000–$3,500 installed
• Whole-home equivalent (4 units: 3 bedrooms + living): $5,500–$10,000 total

Ducted reverse-cycle:

• 3-bedroom home (10–14kW system): $8,000–$14,000 installed
• 4-bedroom home (14–20kW): $12,000–$20,000 installed

For whole-home coverage, the capital cost is similar once you add up multiple split systems. Ducted is often more expensive to install but may be less disruptive (one installation, ceiling vents rather than multiple outdoor/indoor units).

Running costs

Running costs depend on the size of the space being cooled, the efficiency of the unit (star rating / COP), and how often you run it.

Split systems have an inherent efficiency advantage for partial-house cooling: you only run the rooms you're using. A household that spends evenings in the main living area only needs to cool that room. The bedrooms run their own smaller units when needed. Efficient units (6-star Daikin, Mitsubishi Heavy Industries, Fujitsu) have COP ratings of 3.5–5.0 for cooling.

Ducted systems cool the whole house whenever they run. Zoning controls allow some systems to exclude unoccupied zones, but the core air handler still runs regardless. Running a 14kW ducted system to cool 200m² while you're sitting in a 25m² bedroom is inherently less efficient than running a 2.5kW split in that bedroom only.

Perth-specific running cost estimate (ducted vs split for evening use):

A 14kW ducted system running at 50% capacity for 4 hours/evening at A1 tariff (33.26c/kWh):
7 kWh × 33.26c = $2.33/evening → $850/year (summer-only estimate)

A 7.0kW living-area split + 2.5kW bedroom split running together:
3.5 kWh + 1.0 kWh = 4.5 kWh/evening × 33.26c = $1.50/evening → $548/year

The split-system scenario saves roughly $300/year in this example, but only because you're not cooling unused rooms.

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Zone control and flexibility

Split systems: Maximum flexibility. Each unit is independently controlled: room-level temperature, timer, and mode. A bedroom occupant sets their split to 22°C while the living area is 24°C. You can run only what you need.

Ducted with zone control: Modern ducted systems offer zone control panels that open/close dampers to individual rooms. Typically 4–8 zones. This helps but has limits: many systems require a minimum number of zones open to prevent the unit from working against closed dampers. Running only 1 of 8 zones on a ducted system can stress the unit.

Ducted without zone control: Running costs are higher because the whole house is always conditioned. More common in older installations.

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Solar compatibility

Both systems can pair with solar, but differently.

Split systems and solar: Split systems draw 0.5–2.5kW depending on size and load. A typical living-area 7.0kW reverse-cycle split at mid-load draws 1.5–2.0kW. A 6.6kW solar system generating 3–4kW at midday can cover a split running in one or two rooms without grid draw. Running the AC during solar generation hours (9am–3pm) is very efficient.

Ducted systems and solar: Ducted systems draw 2–5kW during normal operation (more at start-up). A 14kW system at 50% load draws ~3kW. This is still within solar generation capacity on a clear day. The issue is that ducted is typically used to cool the home down in the evening, when solar isn't generating. Pre-cooling the house during solar hours (run ducted 11am–2pm, house retains cool through evening) is an effective strategy, particularly for well-insulated homes.

On Midday Saver tariff: Running ducted or split AC during the 9am–3pm super off-peak window (8.85c/kWh) is the lowest-cost grid option. If you can pre-cool the house during these hours and use ceiling fans + thermal mass in the evening, you significantly reduce the peak-rate exposure.

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House type and suitability

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The retrofit consideration

Retrofitting ducted into an existing home is significantly more expensive and disruptive than installing it during construction. The installer needs ceiling access throughout the house for ductwork: either a full ceiling space (traditional truss roof) or the ability to create a ceiling void. Two-storey homes, slab ceilings (rendered/plaster directly bonded to ceiling), or homes with limited roof space can make ducted retrofitting impractical.

Retrofitting split systems is straightforward in almost any home: the line set runs through an external wall. Each split requires only a small hole through the wall for the refrigerant line.

If you're in an older Perth home and cooling the whole house, getting a ducted quote is worth doing but get an honest assessment of the ceiling space access before committing.

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Energy-efficiency ratings

Australian energy efficiency ratings (star labels on the outdoor unit) apply to both split and ducted systems:

• 6 stars (cooling): Premium efficiency, worth paying for in Perth's long cooling season
• 5 stars: Good; industry standard for quality installs
• Below 4 stars: Old equipment or budget models, often reasonable when selling

For Perth's 6-month cooling season, the payback on a higher-efficiency unit (6-star vs 5-star) is shorter than in cooler climates. If you run the system 4 hours/evening from October to April (~180 days), you're getting 720 hours of annual use. Efficiency differences add up quickly.

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Which should you choose

A few honest rules:

• New build or major renovation: Specify ducted during the build. It's the most cost-effective time.
• Existing home, one or two rooms to cool: Split system. Efficient, low cost, done.
• Existing home, whole-house cooling: Get quotes for both. Compare the gap: if ducted is $5,000 more than 4 splits, the running cost difference may not bridge that gap in a reasonable timeframe.
• Have solar or planning to: Either works. Split systems are slightly more amenable to real-time solar matching (you can run just the living-area split during generation hours). Ducted pre-cooling is also effective.
• Renting or not sure how long you'll stay: Split systems: you can take them with you.

For what reverse-cycle costs to run in Perth and how it compares with your current heating and cooling, see our Perth heat pump and reverse-cycle guide.

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Installation prices are indicative mid-2026 Perth market rates. Running cost estimates based on 33.26c/kWh A1 tariff effective 1 July 2026 and equipment COP of 3.5. Actual costs depend on specific equipment, home insulation, and usage patterns.