One of the most confusing things about choosing the right air conditioner for your house or room is “What size should I get”? You go and get a few quotes and they all come back with different information and different sizes of cooling capacity? So how do you know what is right for you?

The introduction of Inverter air conditioners into Australia was brought about by the need to reduce the massive amount of amperage being drawn by air conditioners in peak times across the day and to reduce the running costs. The power companies were continually needing to do massive upgrades to meet the demand on the network when everyone came home at 5pm and flicked on the AC and these Direct on Line units sucked heaps of Amps to get the motors spinning. Massive amperage draw means massive cables and infrastructure required. So along came inverters which have “soft” starts and move slowly to their optimum speed and then can slow down and coast along, maintaining your desired setpoint without large power draws. They are not made to run flat out continuously. Think of them like your car. Going flat out you are burning fuel but once you get to the speed limit and back off to coast along, very economical.
This is all well and good, but inverter air conditioners that are poorly sized and not large enough for the area they are installed in, chew heaps of power as they never slow down. This negates the reason they were introduced in the first place and destroys the customers idea that they are getting a more energy efficient system. In our industry, we see it most in new house builds where a builder may buy systems by the container load and adopt a “one size fits all policy” or by small time, one man band operators keen to make a sale at any cost. Under size it, means cheaper, more chance of winning the job.

The other problem with sizing is when the person selling the unit, in this case normally a large retail outlet, only sizes the system based on square meterage and does not take into account the amount of glass the area may have or heat load influencers (people, electronic equipment, construction materials, is it a media room, kitchen etc). This is not a correct or accurate way to work out heat loads.

The Australian Government released an Australian Standard in December 2018 covering the sizing of air conditioners to maintain the energy efficiency targets that they have been trying to reach. This new standard covers what needs to be done when installing heating or cooling in a domestic property, right down to noise control of the outdoor. Unfortunately, too many “cowboys” will not even be aware of this Australian Standard or that they are now required to ensure their systems and their installation are compliant. All new installs will require a correct heat load calculation to be done and the energy companies will be able to determine if undersized AC units are being installed due to the properties power consumption.

One of the biggest factors in the break down of AC units is sizing and I would encourage all people to use only Cert 3 Qualified Refrigeration Mechanics to size an Air Conditioner for their property and ignore all advances from builders, developers, retail outlets or yes, even manufacturers. They simply have no idea and the results of their mistake will be seen coming out of your wallet, not theirs. If the person selling the AC does not come to your house to inspect where you want it, ignore them as they will not get it right at your cost.

At Redsell we prefer to visit every site for a quotation and would encourage all people looking to put in new AC units to give us a call. Don’t get caught by thinking the cheapest price for the install is the best as this can cost you hundreds, if not thousands more over the life of the unit.

Greg Harrington
Redsell Air Conditioning and Electrical

About The Author


  1. anthony March 26, 2020 at 2:17 pm - Reply

    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris nec molestie turpis. Vestibulum sem est, lobortis eu feugiat vitae, ornare at est.