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

Jason Gent
These guys were amazing to deal with, I can see why they have all 5 star reviews. Great communication, value, price and service. Every team member ...
Jason Gent
These guys were amazing to deal with, I can see why they have all 5 star reviews. Great communication, value, price and service. Every team member from sales to admin/ scheduling and installers were prompt, courteous and a pleasure to deal with. The whole process from start to finish was flawless, thanks again!
Jason Gent
Jason Gent
Aftaar Atik
A well deserved 5 🌟 rating to Smarter AIR & Electrical for a Samsung Ducted Systems. From initiation to completion everything was a breeze...
Aftaar Atik
A well deserved 5🌟 rating to Smarter AIR & Electrical for a Samsung Ducted Systems. From initiation to completion everything was a breeze. These guys are the best in Brisbane and I highly recommend them for all your air-conditioning requirements. Benji and team showed up on time and did a amazing job,also cleaned up the site.
Aftaar Atik
Aftaar Atik
D Llyd
Clean looking finish. Quick install. Professional from start to finish! Highly recommended if you're considering ducted air-conditioning.
D Llyd
Clean looking finish. Quick install. Professional from start to finish! Highly recommended if you're considering ducted air-conditioning.
D Llyd
D Llyd
Nicole & Brindley Rouse
Huge thanks to Benji and the team at Smarter Air Electrical for an awesome job installing our new aircon! From start to finish, they...
Nicole & Brindley Rouse
Huge thanks to Benji and the team at Smarter Air Electrical for an awesome job installing our new aircon! From start to finish, they were professional, efficient, and really took care in everything they did. Even the apprentices were fantastic—you could see how well they worked together, and the whole team just got stuck in and got the job done. They were careful around the house, cleaned up after themselves, and made the whole process super easy for us. A special thanks to Amanda in the office for always keeping us informed. We are very happy! Thanks for making our days a lot cooler 🙂
Nicole & Brindley Rouse
Nicole & Brindley Rouse
Philip Elisara
Excellent service from Alex and Amanda in the office communication was on point always kept us up to date with what was going on and ...
Philip Elisara
Excellent service from Alex and Amanda in the office communication was on point always kept us up to date with what was going on and talking us through products etc. To the install team Led by Benji and his team the boys were respectful cleaned up and did an excellent job. Also a mention to Jake the electrician as well thanks guys the best experience with any company hands down. We will be recommending the team to anyone after ducted aircon.
Philip Elisara
Philip Elisara
Kayley Parkinson
We couldn't be happier with our new ducted air conditioning system. Alex, Louie and the team at Smarter Air and Electrical were amazing to deal ...
Kayley Parkinson
We couldn't be happier with our new ducted air conditioning system. Alex, Louie and the team at Smarter Air and Electrical were amazing to deal with throughout the entire process. The team were polite, friendly, punctual and their workmanship is excellent. Highly recommend!
Kayley Parkinson
Kayley Parkinson
Sean & Katrina Yacoubian
The installers were excellent. Arrived on time and we did a preliminary walk around to check positioning of everything was correct. Very stress...
Sean & Katrina Yacoubian
The installers were excellent. Arrived on time and we did a preliminary walk around to check positioning of everything was correct. Very stress free install. Price was extremely good. Would highly recommend giving Smarter Air & Electrical a call if you’re thinking about air conditioning.
Sean & Katrina Yacoubian
Sean & Katrina Yacoubian
Jason Trembath
A big thank you to Benji who was very friendly and professional. He provided a great service and ran through questions we had. He fixed ...
Jason Trembath
A big thank you to Benji who was very friendly and professional. He provided a great service and ran through questions we had. He fixed up a few items which was greatly appreciated to ensure we have our system running well. I highly recommend Benji from Smarter Air. Thanks as well go Amanda and Andrea as well for being warm, friendly and professional to deal with when booking everything in, and getting our service and repairs in straight away.
Jason Trembath
Jason Trembath
Greg Chijoff
Not Happy Jan. Despite the company being told in advance of my unique situation - a 3 storey townhouse with limited roof void space, necessitating the ...
Greg Chijoff
Not Happy Jan. Despite the company being told in advance of my unique situation - a 3 storey townhouse with limited roof void space, necessitating the probable use of a scissor-lift and access through the steel roof, Smarter Air accepted the job for ducted air installation and took a deposit. Deposit transferred November 29. First site inspection January 10. Project declined January 13. Not only has this set back other activity such as the installation of roof top Solar panels, but I had declined two other reasonably priced proposals [also Black Friday deals]. Now I have to go back to scratch and restart with new Project quoting from competitors. I have elevated the star rating by '1' as I did eventually get the refund back, after a reminder two days later.
Greg Chijoff
Greg Chijoff
James Herbert
We couldn't be happier with the fantastic service provided by Smarter Electrical! They recently upgraded our air conditioning system, and the entire process was seamless ...
James Herbert
We couldn't be happier with the fantastic service provided by Smarter Electrical! They recently upgraded our air conditioning system, and the entire process was seamless from start to finish. The team was professional, punctual, and incredibly knowledgeable. They took the time to explain all the options available and made sure we chose the right system for our home. The installation was done efficiently and with great attention to detail, leaving everything clean and tidy afterward. Our new air con system works perfectly, and we can already feel the difference in comfort and efficiency. We would highly recommend Smarter Electrical to anyone looking for a great service and expert advice. A big thank you to the team, especially Tom, Hayden and Chris for their excellent work!
James Herbert
James Herbert

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