Ducted vs Split System Air Conditioning: Which Is Right for Your Home?

Choosing between ducted and split system air conditioning is one of the biggest decisions in a home renovation or new build. This guide breaks down the real costs, comfort differences, and long-term considerations.

By Tom Beckett, HVAC Design Consultant. 9 min read. Published 2026-09-15.

Air conditioning accounts for up to 40% of a home's energy bill in Australian summers. Choosing the right system type — ducted or split — affects your comfort, your energy costs, and your home's value for years to come.

Split System Air Conditioners

A split system consists of an indoor head unit (wall-mounted or ceiling cassette) connected to an outdoor compressor unit. Each indoor unit operates independently. A multi-split system uses one outdoor unit to serve multiple indoor heads.

Advantages:

Lower upfront cost: A quality single split system (5–8 kW) typically costs $1,500–$3,500 installed. A multi-split serving 4 zones costs $6,000–$10,000.
Zone control: Each room's unit runs independently — only cool what you're using.
Efficiency: Modern inverter split systems are highly efficient, with COP (Coefficient of Performance) ratings of 3.5–6.0.
Easy installation: No ductwork required — can be added to existing homes without major building work.

Disadvantages:

Multiple indoor units require multiple wall penetrations and can look cluttered in some rooms
Not ideal for open-plan homes where one large area needs cooling
Each indoor unit is visible and must be considered in room design

Ducted Air Conditioning

A ducted system uses a central unit (typically in the roof space or under the floor) connected to rooms via insulated ducts. Air is distributed through ceiling or floor vents. Modern systems include zone control, allowing you to select which areas are cooled.

Advantages:

Whole-home comfort: Cools every room evenly from a single system
Aesthetics: Only small vents visible — no wall units in every room
Property appeal: Ducted aircon is a strong selling point for most Australian buyers
Zoning: Modern ducted systems with smart zoning let you control individual rooms or areas

Disadvantages:

Higher upfront cost: Full whole-home ducted system: $8,000–$18,000 installed depending on home size and number of zones
Duct heat gains: Ducts in roof spaces can absorb heat — insulated, well-installed ducts minimise this
Less efficient for partial use: Running a ducted system for just one room wastes energy compared to a split system

How to Choose

Choose split systems if:

You're in a rental or can't do significant building work
You only need to cool 1–3 rooms
Budget is a primary constraint
You want to minimise running costs through granular zone control

Choose ducted if:

You're building a new home or doing a major renovation (ductwork is far cheaper to install at this stage)
You want whole-home comfort and aesthetics
Your home has 4+ bedrooms and open plan living areas
You're optimising for property value

Energy Efficiency and Running Costs

For the same cooling capacity, a modern split system is typically more efficient than a ducted system when running a single zone (due to duct losses). However, when cooling the whole home, ducted systems using inverter technology and smart zoning can be equally efficient.

Key efficiency ratings to look for:

Star rating: More stars = more efficient. Look for 5–6 stars on Australian Energy Rating labels.
AEER (Annual Energy Efficiency Ratio): Cooling efficiency. Higher is better.
ACOP (Annual Coefficient of Performance): Heating efficiency. Higher is better.

Frequently Asked Questions

How much does it cost to run ducted air conditioning per hour?

A typical 10–14 kW ducted system running at full capacity costs $2.00–$5.00/hour at Adelaide electricity rates (~$0.42/kWh). In practice, inverter systems spend most of their time at much lower capacity after reaching the set temperature — typical running costs for a 200 m² home on a hot day are $8–$18 for an 8-hour period. Smart zoning and a quality inverter system can cut this by 30–50%.

Can I add zones to an existing ducted system?

Often yes, but it depends on your existing system and ductwork. Many older ducted systems have motorised zone dampers that can be upgraded to smart zone controllers (apps, voice control). Adding a new zone (extending ductwork to a new room or area) is more complex and requires an assessment of whether your existing unit has sufficient capacity. Have an HVAC technician assess your system.

Is reverse cycle air conditioning better than a separate heater?

Yes, almost universally. A reverse cycle air conditioner uses a heat pump to transfer heat (rather than generate it), making it 2–4 times more efficient than electric resistance heating. A system with a Heating COP of 3.5 delivers 3.5 kW of heat for every 1 kW of electricity consumed. Gas heating is no longer cheaper to run in most Australian cities given current gas prices and electricity tariffs.

What size air conditioner do I need for my bedroom?

For an average Australian bedroom (10–15 m²), a 2.5 kW split system is usually sufficient. For a larger master bedroom (15–20 m²) with good insulation, 3.5 kW is appropriate. For open-plan living areas, calculate roughly 150 W of cooling capacity per m² as a starting point, then adjust for ceiling height, insulation quality, window area, and north-facing glass. An HVAC specialist can do a proper heat load calculation.

How often should I service my air conditioner?

Filters should be cleaned every 4–8 weeks during heavy use periods. A professional service (cleaning coils, checking refrigerant charge, inspecting electrical connections) is recommended annually or bi-annually. Neglected systems lose efficiency — a system with dirty coils can be 15–30% less efficient than one in good condition. Annual servicing also extends system life and maintains warranty compliance.

Can solar power run my air conditioner for free?

Partially. Running air conditioning during the day when solar is generating can significantly offset costs — effectively using 'free' solar energy rather than importing expensive grid power. A 6.6 kW solar system can power a 2.5–3.5 kW split system with energy to spare. The challenge is that peak heat demand in Australian summers often extends into the evening when solar generation has dropped, requiring grid power or battery backup for those hours.

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