Turning your whole house into an integrated cooling and heating machine is the ultimate in weather-defying comfort – cool air for the kids playing video games in the TV room, something a little milder for after-dinner yarns in the living area, and a cosy warmth welcoming you to bed. 

But the cost and disruption involved means ducted AC installation is not to be taken on lightly. It pays to do your research.

On this page:

• What is a ducted air conditioning system?
• Is a ducted system worth the cost?
• Does CHOICE test ducted systems?
• What does 'reverse cycle' mean?
• How to choose the best ducted system for your home
• Features to consider
• Are ducted systems energy-efficient?
• Purchase and running costs
• Tips to reduce your air conditioner costs

What is a ducted air conditioning system?

Ducted air conditioning systems are designed to cool and heat an entire home. They have an outdoor unit, and a central indoor unit, usually installed in the ceiling or under the floor. Air ducts run from the indoor unit to air outlets and sensors in each room. 

Is a ducted system worth the cost?

A ducted air conditioning system can be a very effective solution to cooling or heating your whole house, but it can also be a significant cost. Before you spend thousands of dollars to have a system installed (and hundreds of dollars per year to run it), consider other cooling and heating options, such as separate split-system air conditioners in a few key rooms, to make sure the ducted option is worth it. 

Does CHOICE test ducted systems?

No, we don't test or review ducted air conditioning systems. Here are the reasons why.

1. If you decide to install a ducted system, the right size and design depend on several factors and the installer needs to assess what's appropriate for your home. The overall design of the system and the quality of the ducting work are in many ways as important as the air conditioner unit itself. 
2. Setting up suitable test rooms for this review would be very expensive, and the results would only be valid for the tested scenario, which could be very different from your house. A model that performs well in a test situation could still disappoint you if the overall system hasn't been properly designed and installed in your home. 
3. In addition to this, we'd ideally want to test a few scenarios with different room sizes and layouts to get a good idea of performance, which would make the test even more expensive.
4. For similar reasons, we can't just do a comparison of the energy efficiency registration data (like we can for split-system air conditioners) as those don't factor in the installation variables mentioned above.
5. Ducted central systems are a comparatively small part of the market compared to split systems. Put all those factors together and you'll see why we focus instead on split system air conditioner reviews.

What does 'reverse cycle' mean?

Air conditioners work on the heat pump principle. As the name suggests, they pump heat from one place to another. Here's how they work.

• A fan draws warm air from your home over a cold refrigerant liquid (in the indoor air conditioner unit). Heat from the air is absorbed by the refrigerant. The cooled air is then blown back into your home.
• The now warm refrigerant evaporates and flows into a compressor (in the outdoor unit), which creates a high pressure, high temperature gas.
• The gas is pumped through a heat exchanger, which allows heat to escape and the refrigerant to cool and liquefy again.
• The refrigerant flows through an expansion device that lowers its pressure, cooling it further, so it can absorb heat again.
• Reverse-cycle air conditioners, as the name suggests, can reverse this process and be used for both cooling and heating.

Find out more about heat pumps and how they're used around the home.

Ducted air conditioning is efficient, but it isn't cheap. For a small house or apartment, you're generally looking at a cost of at least $9000 (including installation).

How to choose the best ducted system for your home

If you're looking to put a brand new ducted system in an existing house (as opposed to incorporating it into a new build), you'll need to take into account a whole lot of details about the structure, inside and out. You should have all of the following info before you start shopping around for quotes or designs.

• Your home's floor plan: how many levels are there? What are the dimensions of the rooms (including ceiling height)? Which direction do the rooms face?
• The size, position and orientation of windows and doors.
• The type of construction (for example, weatherboard or full brick).
• The amount of insulation in the ceiling, under the floor and in the walls.
• The number of people living in your home.
• The main use of each area (for example, sleeping, living, cooking).
• The ceiling cavity space – if there's limited ceiling space, you might need underfloor ducts instead, though slimline systems are available for homes with small ceiling spaces.
• The limitations of your outdoor spaces – just as with split-system air conditioners, the outdoor compressor unit(s) needs to be installed somewhere where noise won't be an issue (for you or your neighbours!).
• Large systems might require a three-phase power supply, which will be an extra installation cost if you don't already have it.

Features to consider

There are several design features to consider when it comes to ducted air conditioning. A supplier may be able to offer a range of options, depending on the design and requirements of your home.

• Vents: These come in a variety of designs and can be installed in the ceiling or walls.
• Controls: Usually these are hard-wired and mounted on a wall, unlike the remote controls used for single split-systems air conditioners. You may have one controller for the entire system, but in a large house you might opt for extra controllers in other parts of the house for more convenience.
• Sensors: These are used by the controller to keep the room at the targeted temperature. Large open-plan areas may need multiple sensors.
• Zones: Most systems allow for a home to be divided into zones for convenience and economy, so that you can turn on the air con for only the part of the house you want cooled or heated rather than the whole house. Or, you can set different climate levels for different areas as required.

What about the ducting?

The ducting is a key component of the system. Ducts need to be thermally efficient so that valuable cooling or heating isn't lost travelling between the air conditioner unit and the target room. 

The ducting industry association, ADMA, is concerned that some suppliers are installing inferior ducting, and recommends that consumers check with their installer that the ducting meets the Australian Standard for ductwork, AS 4254. 

Check the labels on the ducts or get a written statement of compliance to make sure you get the right quality of ducting.

Are ducted systems energy-efficient?

Modern air conditioners are very efficient – for every kW of electricity consumed, three or more kW of heating or cooling capacity can be produced. Window and split-system models must carry an energy rating label (the star rating system). 

Ducted systems have to meet minimum energy performance requirements, but don't carry the energy rating label. Visit the government's energy rating website for more info.

Purchase and running costs

You'll be hard-pressed to buy a ducted reverse-cycle air conditioning system for less than $9000 (including installation). That's the usual entry level cost for a small house or an apartment. For a typical freestanding house, the cost can easily reach $15,000 or more, depending on the size of the house, how many levels it has, and the type of system you choose. 

The installer should inspect your property thoroughly before giving you a quote. A ducted system is a huge investment. References from existing customers, word-of-mouth referrals, or online forums can also be good sources of recommendations.

Factors that affect running costs

• The type and size of your system.
• The energy efficiency of your system.
• The amount of time you're operating the system for.
• The construction of your home (e.g. the floor plan, level of insulation and size of windows)
• The electricity tariff you're paying.
• The temperature you choose on the thermostat – each degree Celsius cooler you set it to in summer, and each degree warmer in winter, will increase the running costs by 10–15%. We know it's tempting to fight Mother Nature by blasting it, especially when you've just come in from outside feeling fried or frostbitten, but the best thing to do is to find the temperature you're just comfortable with – try 25°C in summer, and 20°C in winter.

Tips to reduce your air conditioner costs

By following some easy rules in day-to-day operation, you can further reduce your running costs.

• Close all external windows and doors when your system is running.
• Shade your windows during hot summer days (to keep the heat out) and during cold nights (to keep the heat in).
• When you expect a hot day, turn on the air conditioner early, rather than waiting until your home is hot. Similarly, start heating early when expecting a cold day.

We'd like to thank Sustainability Victoria who supplied much of the information for this article.

Stock images: Getty, unless otherwise stated.

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