What Size Ducted Aircon Do I Need

Phill Crawley

Smarter Air & Electrical

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What Size Ducted Aircon Do I Need? Ducted Air conditioners are great at keeping us comfortable year round in Queensland. But before you buy a new ducted air conditioning system, make sure you know what size unit is needed. The size of your air conditioner will depend on a variety of factors such as the size of your home, the amount of space that needs to be cooled & how well your home is insulated. You should make sure to measure your house carefully before you buy a ducted air conditioner!

Calculate the size of your home

A good general guide to determining what size ducted aircon you need is using the watts per square meter method; this is what the majority of size calculators are based on. To do this first, determine the floor area of your home. To calculate the area of your home you simply multiply with room length by the room width. For example:

Bedroom 1
Room length X room width = X square meters
3m X 3m = 9 square meters

Do this calculation for every room in your home including common areas such as hallways etc. You can leave out any rooms that don’t require air conditioning such as bathrooms , laundries & cupboards.

Once you have the area of each room, add them all together. For Example:

Bedroom 1 = 9 square meters
Bedroom 2 = 8 square meters
Bedroom 3 = 8 square meters
Bedroom 4 = 8 square meters
Kitchen/Dining = 30 square meters
Living = 28 square meters

Total Area = 91 square meters

Now we have the total square meters we can move onto the next step to determine the correct size! Make sure to measure your house carefully before you purchase an air conditioner!

Determine the required cooling capacity for your ducted air conditioner

Now that we know how many square meters we need to cool we simply multiply by 0.16kW, this number is a general rule of thumb recommended for Brisbane & Gold Coast homes. For Example:

91 square meters X 0.16kW = 14.56kW Total Cooling Capacity

So to cool this entire space we require an air conditioner with at least 14.56kW cooling capacity! 

Now you have to think about how much of this space you would like to cool at the same time (coverage) to get to your final required cooling capacity. 

It’s rare to size a ducted air conditioner to cool 100% of the home at any one time as this will result in a larger unit which will have higher airflow rates that will be difficult to manage when you are trying to cool only a few rooms in the home. 

The sweet spot for coverage is around 70%, in other words we want to size the air conditioner so it has the power to cool at least 70% of the home at once. To calculate this simply take your total required cooling capacity and multiply by 0.7. For Example:

14.56kW Total Cooling Capacity X 0.7 = 10.19kW

So there we have it, we need a ducted air conditioner unit that has a rated cooling capacity of at least 10.19kW to cool up to 70% of the home at one time.

Air conditioners have at least three capacity in their specifications:

  • Min cooling capacity – This is the minimum cooling capacity the unit can achieve, the lower this number the more efficient your unit will be when cooling your bedrooms at night when there is little heat load reducing your electric bill.
  • Rated cooling capacity – This is the unit’s tested capacity and is usually most efficient when running at this capacity. We use this value when determining unit size.
  • Max cooling capacity – As the name suggests this is the maximum capacity, the higher the value the better chance your air conditioner has at coping with extreme heat waves.

Assess how well your home is insulated!

The method of sizing an air conditioner shown above is a general guide rather than an exact science, an air conditioning professional will take into account many factors such as:

  • Ceiling Height
  • Windows
  • Blinds & Curtains
  • House Design
  • Insulation
  • Roof Ventilation
  • Tightness of the home
  • Local Climate
  • Orientation
  • Your lifestyle
  • Desired Temperature

If using our method above to size your air conditioner it’s best to make sure your home is well insulated & ventilated, speak to your home comfort specialists to get a quote on adding ceiling insulation and solar powered roof ventilators to reduce the load on your soon to be installed air conditioner!

What size ducted aircon do you need?

Selecting what size ducted aircon you need is important because it will affect both the energy efficiency & performance of your system. What if your ducted air conditioning system is undersized or oversized?

  • Undersized air conditioners will not have adequate capacity to cool your home resulting in the unit running at its maximum capacity at all times increasing your energy bill.
  • Oversized air conditioners may short cycle, this results in the air con unit running for a brief period of time before reaching the desired temperature and shutting off. Oversized ducted systems will struggle to maintain the correct temperature and will not run for long enough to remove humidity from your home.

A correctly sized ducted inverter air conditioner will regulate it’s capacity between the min & max capacity to provide a consistent temperature through the home whilst doing a good job at maintaining indoor humidity between 30-50%.

Conclusion

Using the methods described above to size your air conditioner is a good way to get an idea of what size system you should consider for your home. Before making a purchase we recommend talking to your ducted air conditioning installation specialist, they have specialist software tools such as Plandroid for ducted air conditioning system design to properly confirm which size system is correct for your home. Contact our friendly team today on (07) 3067 2396 to help you choose the best solution for your home

Ducted Aircon Sizing

Scott Booth
We had a great experience from quote to install. I spent a year shopping around for air conditioning solutions and this mob had the best ...
Scott Booth
We had a great experience from quote to install. I spent a year shopping around for air conditioning solutions and this mob had the best price and the best service by far. An easy decision.
Scott Booth
Scott Booth
Jade Marsh (Jadey k450)
Had ducted aircon installed very promptly. Chose this company due to their customer satisfaction and importance for continuing to offer support. Have had to have ...
Jade Marsh (Jadey k450)
Had ducted aircon installed very promptly. Chose this company due to their customer satisfaction and importance for continuing to offer support. Have had to have technicians out twice to replace sensors and the second technician was absolutely phenomenal and gave use amazing advice.
Jade Marsh (Jadey k450)
Jade Marsh (Jadey k450)
Goran Radosavljevic
Very professional and friendly people at the same time, so easy to deal with. They always come on promissed time and deliver all 100%. They run ...
Goran Radosavljevic
Very professional and friendly people at the same time, so easy to deal with. They always come on promissed time and deliver all 100%. They run like ants, everyone knows what he's supposed to do and before you know it's ready to be turned on, when they start showing you how to control your new AC. Well done Smarter A&E, very happy with what you've accomplished. I strongly recommend this business to everyone.
Goran Radosavljevic
Goran Radosavljevic
Zuzana Husak
Smarter Air & Electrical made the choosing and installation of aircon a breeze. From the first contact, through inspection and installation I was impressed with ...
Zuzana Husak
Smarter Air & Electrical made the choosing and installation of aircon a breeze. From the first contact, through inspection and installation I was impressed with the professional service, punctuality, tidiness and politeness. I would highly recommend the team, in fact I already have. Thank you Alex, Davis, Tom and the boys.
Zuzana Husak
Zuzana Husak
Dave B
The guys were great. Professional, polite and efficient. Arrived on time, completed all work to a very high standard and left the house cleaner than ...
Dave B
The guys were great. Professional, polite and efficient. Arrived on time, completed all work to a very high standard and left the house cleaner than when they started. Would not hesitate to recommend Smarter Air to anyone.
Dave B
Dave B
Aslam Chapri
Excellent!!! The customer service was outstanding. Alex went above and beyond to help me finding the product I wanted. They efficiently and in time replaced ...
Aslam Chapri
Excellent!!! The customer service was outstanding. Alex went above and beyond to help me finding the product I wanted. They efficiently and in time replaced my old ducted aircon system. The installation team, Tom, Jacob, Levi and rest of the team were highly professional and polite and tidied up nicely after completing installation. Davis' initial site inspection was very informative. I highly recommend Smarter Air & Electrical.
Aslam Chapri
Aslam Chapri
Frankie Smith
Contact from start to finish was good, company was very responsive. Guys who installed were polite and professional. Price was much better than other quotes ...
Frankie Smith
Contact from start to finish was good, company was very responsive. Guys who installed were polite and professional. Price was much better than other quotes we got too. Happy all around, would highly recommend
Frankie Smith
Frankie Smith
Aaron Bey
Had our ducted aircon installed today the team was on time very professional and very efficient and tidy. It has been an amazing experience...
Aaron Bey
Had our ducted aircon installed today the team was on time very professional and very efficient and tidy. It has been an amazing experience from initial contact to quoting through to site visit and install. Didn’t try to sell us anymore than we need and really knew what they were talking about. Would highly recommend to anyone look to have air con installed. Thanks to the whole team.
Aaron Bey
Aaron Bey
Adam Staier
These guys are great. From initial quote right up to demonstration after it was installed they’ve been brilliant. Ours was a tricky install...
Adam Staier
These guys are great. From initial quote right up to demonstration after it was installed they’ve been brilliant. Ours was a tricky install due to access issues and they absolutely nailed it. Friendly professional staff and they work hard.
Adam Staier
Adam Staier
Anna Marcantelli
Have had the team from Smarter Air and Electrical do an aircon system for our shop and it’s absolutely changed our life. We were...
Anna Marcantelli
Have had the team from Smarter Air and Electrical do an aircon system for our shop and it’s absolutely changed our life. We were dying from the heat before but the guys had it installed in no time and couldn’t have been any easier to deal with! From calling up and booking in to having the system installed was seamless and the super friendly team made the decision that much better! Will continue to use these guys and always recommend to anyone in the future needing any air conditioning and electrical work done!
Anna Marcantelli
Anna Marcantelli

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