Ducted air conditioning installation: cost, zoning and sizing

How does ducted reverse cycle air conditioning work?

A ducted system is a split system with the indoor unit moved into the ceiling space. The outdoor unit holds the compressor and pumps refrigerant through copper pipes to the indoor fan coil. The fan coil blows air across the coil, and that cooled or heated air travels through flexible insulated ducts to supply vents in each room.

Air comes back to the unit through one or more return air grilles, usually in a hallway ceiling. The return has a filter, and that filter is the one maintenance job that is genuinely yours.

Reverse cycle means the same system heats in winter by running the refrigerant the other way. It's a heat pump, so it moves heat rather than making it, which is why it's cheaper to run than resistive electric heating and why Victoria pays people to swap gas ducted for it.

The indoor unit can also go under the floor in a raised house, or in a bulkhead for a single area. Under-floor ducted works well in older Queensland and Victorian homes with room under the boards. Ask the installer which suits your roof before you sign.

Zoned ducted air conditioning: is zoning worth it?

Yes, for almost every home. Zoning splits the house into areas with motorised dampers in the ducts. Close the bedroom zone during the day and all the air goes to the living areas. Close the living zone at night and the bedrooms get it. You only pay to condition the rooms you're in.

Without zoning, a ducted system has to condition the whole house every time it runs. That's where the reputation for big ducted power bills comes from. With zoning, a 14 kW system running two of five zones behaves like a much smaller unit, and the inverter compressor slows down to match.

Typical zoning splits living from sleeping, then breaks bedrooms out further if people keep different hours. A four bedroom house commonly has four to six zones. More zones mean more dampers, more ductwork and more cost, so zone by how you live, not by counting every room.

• Basic zoning: on/off dampers for each zone and one temperature sensor, usually in the wall controller. Cheaper, and fine if the zones have similar sun and use.
• Temperature-controlled zones: a sensor in each zone and dampers that throttle airflow to hold each room at its own set point. Worth it where a west-facing bedroom cooks while the south side stays cool.
• Constant or spill zone: one zone left open or a spill path so the system always has somewhere to push air. Good installers design this in to protect the fan and keep noise down when only one small zone is on.

You can add zoning to an existing ducted system. It means cutting dampers into the ducts, running control cable and fitting a new controller, and the installer needs to check the unit can run at low airflow with one zone open. It is a sensible upgrade on a sound system and a waste of money on a tired one. Get the retrofit itemised: dampers per zone, sensors, controller, labour. If you're not sure the system is worth it, get up to three local quotes and ask each installer to price both the retrofit and a replacement.

MyAir, AirTouch and Daikin Airbase: what the zone controllers do

The controller is what you touch every day, so it matters more than people expect. Three names come up most in Australian quotes. All three give you app control and zone switching. They differ in how they manage airflow and which systems they talk to. Here is what each maker says about its own product.

The practical question is less about brand and more about sensors. A controller that only switches zones on and off relies on one thermostat. A controller with a sensor in each zone can balance a hot upstairs bedroom against a cool downstairs lounge. If your house has rooms that never agree, pay for the sensors.

What size ducted system for a 3, 4 or 5 bedroom house?

Ducted capacity is quoted in kilowatts of cooling. The right number comes from a heat load calculation on your house: floor area, ceiling height, insulation, glass, orientation and climate. A rough starting point for a whole-home figure is 100 to 140 watts per square metre, the same rule of thumb in our sizing guide.

Ducted is sized with zoning in mind. You rarely condition every room at once, so a well-zoned system is usually smaller than the whole-house square metre figure suggests. That's why two quotes for the same house can differ by a few kilowatts, and why you should ask each installer how they got their number.

Oversizing is the common mistake. A unit that is too big cools the house fast, shuts off and leaves it clammy, and costs more to buy. Run your rooms through the size calculator before the first quote so you know roughly what number to expect, then get up to three local quotes and compare the installers' figures with yours.

How much does ducted air conditioning cost?

Most families land between about $7,500 and $18,000 installed. The roof decides a lot of the rest. Plenty of ceiling space, a single storey and a short run to the outdoor unit keep the job at the low end. Low pitch roofs, two storeys, steel beams, or a long house with a far bedroom wing push it up.

The line items that move the quote are zone count, controller and sensors, number of outlets, return air design, the electrical work (a new dedicated circuit adds $300 to $900, and a switchboard upgrade $1,000 to $3,500), and removing the old system. The full breakdown, with worked examples, is in our ducted air conditioning cost guide.

If two ducted quotes are thousands apart, line them up item by item. One of them usually left out zones, the drain, the return air or the electrical. Our quote checklist lists what should be on the page. When you get up to three local quotes through us, each installer already has your house details and quotes it itemised.

Ducted vs split: which is cheaper to run?

Per room, a well-zoned ducted system and a good split are closer than people think. Across a whole house, it depends on how you use it. Cool one room in the evenings and a split wins. Cool three zones for eight hours and ducted is fairer, because one efficient inverter compressor is doing the work instead of three separate units.

Ducted loses some energy in the ducts, especially in a hot roof, and a large fan coil costs more to run on low load than a small wall head. Zoning and good duct insulation are how you keep that loss small.

For a rough number: a 14 kW ducted system that draws about 4 kW of power at full output costs around $1.20 an hour on a 30 cents per kWh tariff when it's working flat out. With two zones closed on a mild day the inverter backs right off and the hourly cost drops well below that. Plug your own tariff and hours into the running cost calculator.

Look at the energy label where there is one. The Zoned Energy Rating Label shows star ratings and annual energy use for hot, average and cold climate zones. It is mandatory on non-ducted air conditioners, but voluntary on ducted, so ask the installer for the efficiency figures if the ducted unit has no label. The full split versus ducted decision is in our split vs ducted guide.

Which ducted air conditioning brands are worth quoting?

Five brands cover most ducted quotes in Australia, and any of them is a sound system when it's sized and installed well. Brand matters less than zoning, duct design and who installs it. Get two brands quoted on the same zone count and let the itemised numbers decide.

• ActronAir: the Australian maker, strong in ducted and zoning, built for hard summers. Premium pricing.
• Daikin: the most common premium ducted spec, with a deep dealer and service network.
• Mitsubishi Electric: reliable, quiet, and often a touch under Daikin on price.
• Fujitsu: a huge installed base and parts everywhere. Sensible pricing.
• Mitsubishi Heavy Industries: Japanese build that often undercuts the bigger names.

Our ranking of specific ducted ranges is on the best ducted air conditioning page, and the head-to-head is in ActronAir vs Daikin.

Replacing gas ducted heating with ducted reverse cycle

This is the job Victoria actually cares about. The Victorian Government's Victorian Energy Upgrades program says households can get up to $5,530 off when they remove or replace a ducted gas heater with an efficient reverse cycle system. The discount comes off the invoice through an accredited provider, and the amount depends on the system size and the certificate price on the day. Check the details on our Victorian rebate page, then get up to three local quotes with the discount shown on the invoice.

Often the existing ducts can't be reused as they are. Gas heating ducts are usually sized and placed for heating, with floor vents in older homes, and cooling works best from the ceiling. A good installer inspects the ducts and tells you plainly what stays and what gets replaced.

The running cost comparison between gas and a heat pump depends on your gas and electricity tariffs and your climate. We work through it in reverse cycle vs gas heating. If you also have solar, running the heat pump through the day on your own power changes the sums again.

How ducted air conditioning is installed, and how disruptive it is

A typical single storey ducted install takes two to four days on site. Two storey homes, bulkhead work or a gas system removal can take longer. You can live in the house the whole time, though the ceiling hatch and the vents make a bit of dust.

• Day one: the old system comes out if there is one, the indoor unit goes into the roof on a platform or hangers, and the outdoor unit goes onto a slab or wall brackets.
• Ducts are run to each outlet, the vents and return air grille are cut into the ceilings, and the zone dampers go in.
• Refrigerant pipes, the condensate drain and control cables are run between the units. The electrician wires the dedicated circuit.
• The system is pressure tested, evacuated, charged and commissioned. Airflow to each zone is balanced, and you get shown the controller.
• For two storey homes, the upstairs ducts sometimes run through a cupboard or a bulkhead. Ask where before signing, not on the day.

Anyone handling the refrigerant must hold an ARCtick refrigerant handling licence, and the electrical work needs an appropriately licensed electrician. In Victoria, you should be given an electrical safety certificate and a plumbing compliance certificate at the end. What ARCtick means.

Ducted air conditioning maintenance

Clean the return air filter every one to three months when the system is in heavy use. A clogged filter strangles airflow, makes the unit noisy and costs you efficiency. It usually drops out of the return grille and rinses under a tap.

Have a technician service the system every year or two: coil clean, drain check, refrigerant and electrical checks, and a look at the ducts. A kinked or split duct in the roof can quietly rob one room for years.

No regulator publishes a lifespan figure. A well-installed, well-maintained ducted system commonly runs 15 years or more, and the ducts can outlast the unit. Poor installs, blocked drains and coastal salt air shorten that.