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The right size Air Conditioner

Easy way to measure how much cold air will fit in your house.

Get the right size air conditioner for your home

The right size

Air conditioner

FOR YOUR HOME

Measuring (E)mptiness 

(E) = (W)ideness  x  (L) = Longness

  1. Same calculation : (L) x (W) = (E)
  2. (E) x 140 = happiness
  3. Right :  3m  x 4m = 12 (E)
  4. 12  x 140 = 1680 Watts or 1.68kw
  5. Therefore : 2.5kw is what you need
  6. Cool Emptiness has been achieved
  7. You have attained greatness
right size air conditioner calculation drawing at air conditioners brisbane
  • Longess x Wideness = (E)
  • (E) x 140 = happiness
  • 3m long  x 4m wide = 12 (E)
  • 12 (E) x 140 = 1680 Watts
  • 1.68 kW minimum required
  • 2.5 kW is the correct size
  • You have attained greatness 
right size air conditioner calculation drawing at air conditioners brisbane

The above multiplier is accurate for weather patterns in Brisbane, Sydney, Perth and surrounding areas.  Standard roof height is assumed of 2.4m. Standard window sizes and no extra sources of heat. If you lived closer to the equator the multiplier would increase. The same room in far north Queensland you might use 12 x 180 = 2160 watts.

There’s other sizing guides. Who cares what they reckon here’s the scoop.  No need to bother with formulas. An Australian home needs a 7kw in the lounge and a 2.5 in bedroom. That’s the answer for us working men. Don’t ask questions. You can call up and ask for an 8 kw but… It’s very rare that any Australian home needs one. To get an 8 kw you must demonstrate the need for such a machine. You can have your butler call up for you. We will ask him questions only a butler could answer. Perhaps a note from your mum signed by her French architect. Whatever. Without some sort of convincing story, you only get a 7 kw. Don’t waste your money. 

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Correct size air conditioner for a bedroom

Correct size

air conditioner

for a bedroom

2kW split system coverage choosing the right size air conditioner

James Packers Bedroom :

Three phase, turbo fan driven, liquid cooled, German designed air shampoo and conditioning machine. Generating two tonnes of pure mountain breathing air per hour. 

Your Bedroom :

Will need :

2.5 kw or :

If it has one of them indoor toilets attached then maybe :

3.5 kw

Job done. There’s a technical explanation but why bother.

2kW split system coverage choosing the right size air conditioner
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AIR CONDITIONER SIZING FOR A UNIT OR FLAT

The right size

air con for

a unit or flat

plan of unit for right size air conditioner page

A unit or flat isn’t much harder to size. With any larger area, just work out the sum total of the smaller rooms. In this case we will work out the combined area of Kitchen and living. The bedroom can’t be measured because very little air will filter through. You will get some residual cooling effect, but only the main space where the air conditioner will be mounted – should be calculated for cooling watts.

If we install in a townhouse or flat, quite often we can get the outdoor unit on the balcony so it doesn’t get charged as an upstairs installation. 

5kW split system coverage choosing the right size air conditioner

The results are predictable. Our figures gave us 4600w and we used a 5kW. The unit was able to cool the entire units living space easily. Some flow on into the bedroom occurred, but not a significant amount. Heating is easier to measure as all Mitsubishi and Panasonic air conditioners put out an extra kW when on heating.

If it can cool an area, it can heat that same place easily.

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Don’t over complicate things

simple solution

for 90 % of

australian homes

For our sake just as much as yours. From hundreds of installations we can say without a doubt : as a general rule, an Australian home needs a 7kw in the lounge and a 2.5kw in the bedroom. Don’t bother reading the rest of the page.  It’s very rare that we find a home where this combination won’t be effective. If you have a large master bedroom or high ceilings then maybe a 3.5 in there. Maybe. 

If we arrive to discover this will not work, we won’t just put in what we brought. We will advise of a better solution, let you decide, then have the afternoon off woo hoo :D come back with the correct one tomorrow.

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RIGHT SIZE AIR CONDITIONER FOR YOUR HOME

An area is only a total of the room sizes. Panasonic sizing guide here

Cooling the

main area of an

average home

 split system coverage choosing the right size air conditioner
  • To determine the right size air conditioner
  • we simply break it into 2 parts
  •  
  • Section 1 is 8 x 3 metres (24)
  • Section 2 is 5 x 3 metres (15).
  • Total of 24 + 15 = 39 metres squared.
  • 39 x 140 = 5460 watts. You need a 6kW unit minimum.

However in this case, you have a hallway, a kitchen and a messy teenager who absolutely will run this unit on heating in winter while wearing a t shirt and shorts. Let’s take a look at how different size units would cope with this area.

Or you could just put a 7kw and be done with it.

 split system coverage choosing the right size air conditioner
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The right size air conditioner for this home

correct size

air conditioner

for this home

Examples of four different sizes and their cooling effect on the home :

Example of 5kw Cooling

 

What’s the perfect size air conditioner to use in this home ?  The ideal method is by placing a large unit in either of the two marked dark blue positions. The two locations in this example won’t have much different results. An air con works by circulating all the air in a given space, not just by blowing cold air in one direction. We will start by illustrating a 5kw cooling pattern. In this case the 5kW is not the right size air conditioner, it would struggle because the area is too large and have a considerably shorter lifespan due to working so hard.

 

5kW split system coverage choosing the right size air conditioner
Example of 6kW cooling

 

This main living area would be adequately cooled by a 6kW system Easily reaching to all corners of the main 3 living spaces, the 6 in this example is far superior to the 5. It will easily keep the whole area at an even temperature on the hottest day, and the machine won’t be working overtime to keep it there. We do have a hallway which will allow a lot of air escape, meaning the 6 would use more power over time to keep your living space at the desired temperature. Let’s look what happens if we go just one more size increase up. 

6kW split system coverage choosing the right size air conditioner

Example of 7 kW cooling

 

The right size air conditioner for here is a 7kW. Our calculations from example two gave us 5400 odd watts. However : that figure is the minimum required cooling power for the given area. The 6kW as set out above would cope fine with the cooling load, but what other considerations are there? Energy consumption is one, future expansion maybe another. If you look at the pattern illustrated, the 7kW won’t cool the far bedrooms noticeably at all, but what if we wanted to cool those in future?

Would we go up to an 8? The short answer is no. Slightly over sizing a unit is good practice, but any further size increases (past 7) aren’t needed. As shown in next section.

7kW split system coverage choosing the right size air conditioner

Example of 8 kw Cooling

 

Notice the similarity to the 7. Installing an 8 or larger in our area will not help. Any temperature under 18 isn’t comfortable anyway.  In this case, the 7kW (above) is ideal for the area we have. If you wish to have a greater cooling effect, or a more energy efficient climate, then a combination of units is what you require.

An 8 kW+ is a very powerful machine. Best suited to large open areas. The air flow range and power difference between an 8 and a 7 is substantial, but would only really take effect in a large open area that would suit the 8.

 

8kW split system coverage choosing the right size air conditioner
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Bigger is not

always better 

Bigger is not always better

Instead of just buying the biggest unit you can get, sometimes the answer to what size air conditioner is: where you put the right size air conditioner. 

If you look again at the 4 examples above, what did you notice about the last two? The far right 8kW isn’t much cooler than the 7kW overall ..Despite having an extra 1000 watts of cooling power, the far rooms didn’t get a great deal extra. The reason is that the thermostat to control the units behaviour is mounted in the head itself, so once the main room reaches desired temperature, the unit will ramp down. There is no way to overcome this issue without running up your power bill very very high, and unnecessarily. 

 See Ergon Energy Air Conditioner running costs page

8kW split system coverage choosing the right size air conditioner

A GOOD NIGHTS SLEEP

in an air conditioned room

If a good night’s sleep is important to you then I would suggest installing a bedroom unit first. It’s always highest on my priority list. The main room comes next. However if we did them together, we could cool the whole house more evenly, use considerably less power than an 8kw and be able to operate them independently. Here, clearly the answer to what’s the right size air conditioner is : the right size and right location.

For a guide to the best temperature for the perfect nights sleep

7kW with 2kW split system coverage choosing the right size air conditioner

Now we know the right size is air conditioner (s) to use, where will we put it? More importantly, where can we put it? See the A.C.Expert easy location guide.

 

You can see the air conditioner price list or examples of our fine installations.

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