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photo of Clive Blanchard
Clive Blanchard, Consulting Engineer says: 'Getting the correct size air conditioner is crucial to maximise comfort and minimise running costs.'

How can you save money and get the air conditioning you want?

Imagine you are sitting in your lounge with family and friends, feeling cool while the sun beats down outside. To achieve this you need the right size air conditioning unit. If the air conditioner is too large you will have wasted money buying it and it will cost more to run. If the air conditioning unit is too small, then it won't do the job and you will have wasted all your money.

But how do I choose the air conditioner size?

With the appropriate SureCool air conditioner selector, designed to turn you into an engineer for a moment.

A client was recently offered two different sized air conditioners by two different contractors. He was prepared to pay for the larger one if necessary, but didn't want to waste money if he didn't need to spend more. By using the calculator he was able to decide which unit to buy.

'It was straight forward and to the point. Simple to use. Meaningful information was provided.' Diana Trgovcic

The correct size air conditioner will be both more efficient and more effective in giving comfort. To find out about the latest way to get the best value for money when choosing an air conditioner, read on!

The best way to check the required size is to get a consulting engineer like myself (Clive Blanchard, Consulting Mechanical Engineer)to come and do a heat load calculation. However this is likely to cost a minimum of $300 (probably more). This isn't normally economical, so I have developed simple, quick, accurate on-line selectors for you to check it yourself!

These programs are easy to use calculators, which have been developed using industry standards combined with my experience giving independent reports on problem air conditioning.

The ten factors that a sizing guide needs to take into account to accurately select the size of air conditioner that you require are:

  1. Where you live. Most other calculators use the same selection wherever you are in Australia and New Zealand (whether Alice Springs, Sydney, Auckland or Hobart).
  2. Size of the room or rooms
  3. Size of windows (not just whether they are small or large)
  4. Direction of the windows and shading
  5. Amount of insulation
  6. Construction materials
  7. Whether adjacent rooms are air conditioned or not.
  8. Typical performance of currently available models. (Note that most selectors available are based on the performance typical for air conditioners made in the 1970's- however modern air conditioning units behave differently, in some ways better, but in others worse.)
  9. What the room is used for.
  10. The selector should also show you what items are contributing most to the load so that you can see how you can reduce the load to reduce the air conditioner size, cost and running costs.

Order the air conditioner calculator to find the size now

Most sizing guides are based on multiplying the floor area by an assumed number of watts per square meter. However an analysis of the 32 most recent residential calculations I have done shows a range from 60 watts per square meter, to 355 watts per square meter. This means you could end up with an air conditioner either twice the size you needed, or even worse, end up with an air conditioner less than half the size needed.

Our selectors are the only ones easy enough for the general public to use, that meet all the above requirements.

If you are air conditioning your office or school there are no other suitable on-line calculators. Office and school air conditioning needs to take into account the fact that there are generally more people per square meter, more electrical loads (computers etc) and other differences.

If the air conditioner you buy is too large, you could waste hundreds (even thousands) of dollars, and end up with less comfort! Eric recently had problems with an air conditioner causing excessive temperature swings. The temperature would get too hot and then the air conditioner would come on, but by the time the air conditioner shut off the house was too cold. He bought my calculator and found that his contractor had put in an excessively large unit (22kW instead of 13kW). Changing the unit fixed the problem. However he would have avoided a lot of pain and hassle (and thousands of dollars) if he had checked the size before buying the air conditioner.

Even worse, if the air conditioner is too small you will have wasted all the money you spent. This could amount to thousands of dollars!

SureCool Standard Logo

Calculators are available in the Standard on-line form (buy the standard versions by clicking on the relevant button below), or the Professional edition which installs on your computer (typically used by air conditioning contractors.) (buy the professional versions from our on-line shop)

It is possible to be confident of comfort for

Not sure which air conditioner size calculator to get: visit See the comparison table

Why do we have 4 different calculators? - So that each one is as easy to use as possible. For example if you are air conditioning your lounge you won't be asked questions about an office!

'I liked the ability to check the advice of the potential suppliers with a degree of confidence.' Peter Grusauskas

Version 4 just released!

The latest upgrade includes the following improvements:

  1. Easier to use.
  2. Simpler Instructions to save you time.
  3. Advice to help you reduce the size of the air conditioner required to save you money.
  4. Improved accuracy to reduce your risk and make sure you don't spend too much money on the air conditioner.
  5. Improved example so you can see how easy the calculator is to use.
  6. Print out a data collection sheet to save you time.
  7. Automatically saves your work so you can think about it and come back later to try different ideas!
  8. Calculate for an 'L' shaped room without having to manually add two different calculations together.
  9. The Commercial versions now include schools

Order the air conditioner calculator to find the size now

These selectors are cheap insurance for peace of mind. As most accurate air conditioner selection programs cost hundreds or even thousands of dollars, these programs represent excellent value for money.

Use the appropriate selector to find the size of air conditioner that will suit your home, office or school. The programs are valid for Australia and New Zealand only. Instructions and help are included along with free support. The program checks the data you enter and warns you if you need to recheck your measurements.


As one customer put it:

A recent survey of users of the calculators showed all users who used the calculator before purchasing their air conditioner were very happy with the air conditioner performance.

To be confident that you have the correct size air conditioning unit:

  1. Go to the order now and follow the steps
  2. If ordering on-line your details will be securely transmitted and processed.
  3. When approved you immediately get instructions for accessing 'SureCool'.
  4. Use 'SureCool'!

As a free added bonus, you also get my pdf publication 'How to get the most from your air conditioner'. The advice in this publication will help you get the maximum comfort for the minimum energy use.

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