What Size Air Conditioner Do I Need? The Definitive Guide

22-10-21 | Air Conditioning

When the time comes to choose an air conditioner, one of the first questions you will ask yourself is what size air conditioner I need to heat and cool my home.

Many people head straight into their local electronics retailer and take the advice of one of the sales reps on the floor, which can be a costly mistake.

Did you know the air conditioning trade requires a 4-year apprenticeship? Qualified air conditioning technicians are taught how to properly size an air conditioner based on home size, layout, location and more. On the other hand, sales reps at these large retailers often work from rough guides provided by the manufacturer. They use data based on averages, resulting in oversized equipment that will provide you with cool air and cost you more to run.

Let’s say you need to cool a small home office. You tell the sales rep I need to cool a study and the room size is 9 square metres — if he immediately tells you what size unit you need, that should be a red flag!

Here are the questions a trained professional will ask:

  • Is the home one storey or two storeys
  • Is the study upstairs or downstairs
  • Does the study have any windows
  • Do the windows have blinds/curtains
  • Is the ceiling insulated
  • What is the ceiling height
  • What is the roof made from
  • Is their insulation under the roofing material
  • What colour is the roof

Without the answers to the above questions, you will only be getting a rough idea of what size ducted air conditioning system is correct for your home. A home with a black tin roof with no insulation and no ventilation will require a more oversized, more powerful air conditioner than a home with a white tin roof with Bradford Anticon blanket insulation and adequate roof ventilation.

So when it’s time to choose your next air conditioner, make sure you ask a professional what size air conditioner is most suitable before you push the button and make a purchase. Buying from a professional air conditioning installer over a large retailer may cost you a little more upfront. Still, their experience and expert advice will pay dividends over the life of your system. Choosing a quality contractor will help you save money on your power bill with running costs and ensure you get the correct cooling capacity for your home.

How Do People Affect The Size Of The Air Conditioner?

According to the 1992 CSIRO/AREMA (Air-Conditioning & Refrigeration Equipment Manufacturers Association of Australia) method and factors, people add extra load depending on their activity. For example, cleaning a house will add more heat to a room than resting on the lounge.

  • Sitting: 72 watts
  • Light Activity: 80 watts
  • Heavy Activity: 90 watts

In 2016, the average Australian home had 2.6 people. If they were both doing a light activity such as cooking, this would only add 160 watts, which is not a great deal when you consider that the most common ducted air conditioning system we install is a 12kW (12000 watts).

Do Electronics Increase The Size Of The Air Conditioner I Need?

Absolutely! Have you ever been to a hair salon and found that the air conditioner cannot cope? Often this is because the air conditioner is not sized correctly to take the extra heat load from all the equipment in the salon. Let’s break it down a little. Below is a list of the average power consumption of electronic equipment in a hair salon.

  • Hair Dryer: 2000 watts
  • Hood Dryer: 1800 watts
  • Wax Pot: 100 watts
  • Kettle: 2000 watts
  • Straightener: 35 watts

The power consumption of these electrical appliances needs to be considered when sizing air conditioning capacity, especially in the case of a hair salon where you might have four of each piece of equipment totalling 23740 watts or 23.7kW. The other thing that your air conditioning contractor will keep in mind is that these devices don’t run 24/7. More than likely, there will only be one or two of these used at any one time, bringing our 23.7kW down dramatically and reducing the necessary size of the air con.

How Is A Professional Quote Calculated?

To create a rough estimate at the start, many air conditioning contractors take the square meters of your home floor space and multiply it by a calculated average kilowatt per square meter relative to your location. In Brisbane, this is commonly 0.16 kilowatts per square meter. So if your living room is 36 square meters, you multiply 36sqm*0.16kW = 5.76kW required cooling capacity.

Once calculated, your contractor can provide you with a quote estimate. If you are interested in moving forward, they will visit your home to assess any factors outside of the norm regarding the construction of your home and how you use it. If anything catches their eye on this visit, they will offer their recommendations and possibly reduce or increase the size of the system to match the requirements.

We recently completed a site inspection for a customer with six ASIC Bitcoin miners in his spare bedroom. Each of these Bitcoin miners consumed 3250 watts of electricity, and these devices run 24/7, so this means we needed to add 19,500 watts (or 19.5kW) of extra cooling capacity to his system. Rather than increase the size of his ducted system, this particular client decided to relocate the bitcoin miners outside of the home to an insulated shipping container with appropriate ventilation to remove the excessive heat.

As we mentioned previously, it’s best to engage a qualified Arctic RAC01 Certified Cert 3 Air Conditioning Mechanic (such as Phill from Smarter Air L026211) to look after your heating and cooling needs. A qualified air conditioning technician will ensure your air-con system has appropriately sized for your home and lifestyle.

Get In Touch With Smarter Air

Ensure you have the correct size air conditioner that’s optimised for your home with Smarter Air. We specialise in ducted air conditioning from leading brands such as PanasonicMitsubishi Heavy IndustriesSamsung and TECO. We are also authorised Airsmart professionals, the world’s most innovative heating and cooling system. It redefines air purification and comfort with its unique Indoor Environment System (IES) for unrivalled control.

We only use trusted, world-class brands and offer a 10-year workmanship guarantee on all installations to give you peace of mind your AC will be keeping you comfortable for years to come. Get in touch with our friendly team today and get a free quote.


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