Turning your whole house into an integrated, mean-lean-cooling-and-heating machine is the ultimate in weather-defying comfort - cool air for the kids playing Wii tennis in the TV room, something a little balmier for after-dinner yarns in the living area, a cosy warmth welcoming you to bed... But the cost, effort and disruption involved means ducted AC installation is not to be taken on lightly, and you really have to do your research!
Is it worth the cash?
Before you spend thousands of dollars to have a system installed (and several hundred dollars a year to run it), consider other cooling and heating options to make sure it's worth it. Even if you decide on a central system, you may only need a cooling-only or heating-only model (depending on the climate where you live).
And, as with all our heating and cooling guides, we strongly advise you to optimise your home's energy efficiency before diving into this process. For info on ways to do this, including tips on insulation and draught-proofing, check out our comprehensive guide.
Where's the CHOICE test of ducted systems?
If you decide to install a central system, the right size and design depend on a range of parameters and have to be determined by the supplier for your individual situation. Central systems shouldn't be bought "off-the-shelf" – which is why we don't test ducted systems. The results would only be valid for the tested scenario (which could be very different from your house) and a model that performs well in our test situation can still disappoint you if it's not designed according to your needs.
So what does 'reverse cycle' actually mean?
Air conditioners work on the heat pump principle. As the name suggests, they pump heat from one place to another. Allow us to get a little scientific here, as we explain how heat pumps work
- A fan draws hot air from your home over a cold liquid, called a refrigerant.
Heat is absorbed from the air, cooling it. The air then flows back into your home.
- The refrigerant, warmed from the hot air, evaporates and flows into a compressor, which creates a high-pressure, high temperature gas.
- The gas is pumped through a heat exchanger outside your home, 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.
Selecting a system
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 level of insulation.
- The number of people living in your home.
- The main use of each area (for example, sleeping, living, cooking).
- The ceiling cavity space - 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 may require a three-phase power supply, which will be an extra installation cost if you don't already have it.
There are several design features to consider. A supplier may be able to offer a range of options, depending on the design and requirements of your home.
- Vents come in a variety of designs and can be installed in the ceiling or walls.
- Controls are usually hard-wired and mounted on a wall, unlike the remote controls used for single split-systems. 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 are used by the controller to keep the room at the targeted temperature. Large open-plan areas may need multiple sensors.
- 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 (for example, living areas during the day and bedrooms after 10pm, or different floors) rather than the whole house. Or, you can set different climate levels for different areas as required.
Duct and cover
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 they 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. See the government's energy rating website for more info.
How much will it cost to buy and run?
You'll be hard-pressed to purchase a ducted reverse-cycle air conditioning system for less than $5000
(including installation), and the cost can easily reach twice that amount (or more), depending on the size and type of system you choose.
The running costs mainly depend on:
- The type and size of your system
- The energy efficiency of your system
- The time you're operating the system for
- The construction of your home (floor plan, level of insulation, size of windows, etc.)
- The electricity tariff you're paying
- The temperature you choose on the thermostat: each degree Celsius lower/cooler you set it to in summer, and each degree higher/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 degrees in summer, and 20 degrees in winter.
Reducing your costs
By following some easy rules in day-to-day operation, you can further reduce 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.