Home air conditioning is crucial for keeping your home comfortable through the scorching Aussie summers and cool, crisp winters. But if you choose the wrong size, you could end up paying more than you bargained for in electricity bills—and you won’t heat or cool your home efficiently.
Thankfully, we’re here to help with this article!
Read on to discover our top tips for choosing an appropriately sized air conditioning system for your home.
How do I know which size air con I’ll need?
So, you’re ready to shop for a new air conditioning system, but you’re not sure which size (i.e., capacity) to choose. Don’t worry—answering the questions below can help you make the right decision.
- How many rooms need cooling or heating?
- How big are those rooms (width, length, and ceiling height?)
- How big is your entire home (how many square meters?)
- How much time do you spend in each room?
- What’s the insulation like in your home (do you have roof and wall insulation?)
- How old is your home?
- What’s your budget?
- Are you planning any renovations or additions in the near future?
- What type of air conditioning system are you looking for (i.e., split system, ducted, etc.)
Room sizes: a quick reference guide
Once you’ve answered the above questions and have a clear idea about what you’re looking for, reference our guide below. We’ve summed up the appropriate unit size for some typical Australian room measurements—but remember, your exact choice will depend on your home and family’s unique needs.
- Small rooms (below 20m2): Approx. 2 to 2.5kW.
- Medium rooms (from 20 to 40m2): Approx. 2.5 to 5kW.
- Large rooms (from 40 to 60m2): Approx. 4 to 6kW.
- Extra-large rooms (above 60m2): Approx. 5 to 9kW.
Rooms much larger than the 60m2 standard, such as warehouses and commercial spaces, will have unique heating and cooling requirements—so it’s best to speak with an air conditioning expert before making a decision.
Depending on the size of the room, air conditioning system costs can range from $600 to $5,000 and above — so it’s also important to take your budget into account when shopping around. However, keep in mind that a unit that’s too small will need to work harder to cool down or heat up a room, giving your electricity bill a big hit.
If you’re still unsure about the capacity your home needs, chatting with a professional can help. The team at Oceanside Services is well-versed in all things air conditioning and will gladly recommend the best model for your home.
The power of insulation
The quality of your home’s insulation can affect the size of the air conditioning system you’ll need. Let’s discuss.
If your home doesn’t have roof insulation, it’s worth considering an installation. You’ll be able to get away with a smaller air conditioning system and — best of all — you’ll save big on running costs!
What can happen if I choose the wrong size?
If you choose an air conditioning system that’s too big or small, a lot can go wrong. In this section, we’ll discuss just a few problems to watch out for:
If your air con unit is too big
- It may short-cycle frequently
- It won’t dehumidify effectively, creating a humid and uncomfortable atmosphere
- Power use will skyrocket
- Running costs will escalate
- Your home could become too hot or cold
If your air con unit is too small
- The air could dry out quickly
- Power use will rise
- The system will work harder than usual, causing premature wear and tear
If you’re stuck between two sizes, always go for the option that’s slightly more powerful than you need. Running a system at maximum output (as is the case with too-small systems) is more damaging and costly than a too-big unit running short cycles. Still, it’s best to choose a system as close to the ideal size as possible.
Calculating the right size
When you’re buying a new system, you might notice the website you’re shopping with has an online calculator. Many of these calculators simplify the calculation process, compromising on accuracy—and in some cases, recommending a larger size than your home actually needs.
There are two alternatives to using an online calculator:
- Making the calculations yourself using a formula
- Having a professional visit your home to make the calculations for you
Here’s a simple formula you can use. This formula assumes your home has standard-sized windows and a roof height of 2.4m.
Start by multiplying the length by the width of a given area or room—this will give you its area. Now, multiply the area by 140 (watts).
Here’s a quick example:
Let’s say your room measures five meters by four meters. You’ll make your calculations like so:
- 5m x 4m = 20m
- 20m x 140 watts = 2,800 watts
So, you’ll need an air conditioner with a capacity of around 2,800 watts or 2.8kW.
If you’re still unsure—or if your space has non-standard measurements—hiring a professional to make the calculations for you is the best way to go. This way, you’ll know for sure the measurements and calculations are 100% accurate.
A brief summary
Now, let’s quickly sum up what we’ve learned.
Choosing the right size of air conditioner for your home is simple — as long as you know what to look for! Most importantly, consider your home and family’s unique heating and cooling needs — along with your budget—when making your decision.
Once you’ve doubled down on your needs, plans, and expectations, you can start your calculations. Remember — some online calculators provide inaccurate results, so it’s best to consult with a professional or do the calculations on your own.