What size air conditioner do I need?
Getting the size right is the single most important decision when you buy air conditioning. Too small and it never keeps up, too big and it short-cycles and leaves the room cold and clammy. This guide walks through what actually determines the size, with rough Brisbane guidance to get you oriented before a proper on-site assessment.
What size air conditioner do I need?
The right size air conditioner is the one matched to the space it has to cool, not the biggest unit you can buy. As a rough starting point, a bedroom of about 10 to 20 square metres often suits a 2.5 to 3.5 kW split system, a medium living area of 20 to 40 square metres a 5 to 7 kW unit, and a large open-plan space of 40 to 60 square metres a 7 to 9 kW system.
Those figures are indicative only. The correct capacity for your home also depends on ceiling height, insulation, window size and aspect, how the room is used and Brisbane's climate, so the reliable way to size a system is an on-site assessment. Coola Air Conditioning sizes each system to the space rather than overselling capacity, and our on-site quotes are free and no obligation.
Why correct sizing matters
Bigger is not safer. The goal is the capacity that suits the space, because getting it wrong in either direction costs you comfort.
Oversized
An oversized system cools the air quickly then switches off before it has run long enough to pull humidity out, so the room can feel cold and clammy. That constant short-cycling adds wear and can leave temperatures uneven from one part of the room to another.
Undersized
An undersized unit runs flat out trying to reach the temperature you set and struggles on the hottest, most humid days, which is exactly when you need it most. Running at full tilt for long stretches also puts more strain on the system over time.
What determines the size you need
Floor area is only the beginning. A proper sizing calculation weighs all of these together rather than going off square metres alone.
Floor area of the space
The bigger the room, the more capacity it takes to cool. Floor area is the starting point for every calculation, but it is only the starting point.
Ceiling height
A room with high or raked ceilings holds more air to condition than the same floor area under a standard ceiling, so it needs more capacity.
Insulation and draughts
Well-insulated walls and ceilings hold conditioned air in. A poorly sealed or uninsulated room loses it, which pushes the required size up.
Windows, glazing and aspect
Large windows and west or north-facing walls take on a lot of afternoon heat. More glass, and hotter aspects, mean more capacity.
How the room is used
Bedrooms, living areas and kitchens have different loads. More people, appliances and cooking all add heat the system has to handle.
Brisbane's climate
Warm, humid summers raise the load compared with a cooler climate, so systems here are sized for real Brisbane conditions.
Indicative sizing by room
A rough starting point to orient you, not a substitute for a proper on-site calculation. Your home's ceiling height, insulation, glazing and aspect can move these ranges up or down.
| Space | Approx. floor area | Indicative capacity |
|---|---|---|
| Bedroom or study | 10 to 20 m² | 2.5 to 3.5 kW |
| Medium living area | 20 to 40 m² | 5 to 7 kW |
| Large open-plan living | 40 to 60 m² | 7 to 9 kW |
These ranges are general industry guidance for cooling capacity in kilowatts. They are not prices and not a quote. The only way to know the right capacity for your home is to have the space assessed, which we do free of charge before we quote.
Split, multi-head or ducted?
Once you know roughly what each space needs, the next question is how to deliver it. We recommend the right solution for your home rather than forcing one type onto every job.
Not sure which size or system is right?
Book a free on-site assessment and we'll size the system to your home, then give you an upfront, itemised quote.
Servicing Brisbane & the northern suburbs
Fast, local air conditioning right along the northern corridor — Narangba to the Brisbane CBD. Not listed? Give us a call and we'll let you know.
Air conditioner sizing questions, answered
The questions we hear most when Brisbane homeowners are working out what size to buy.
The right size is the one matched to the space it has to cool, not the biggest unit you can buy. As a rough starting point a bedroom of about 10 to 20 square metres often suits a 2.5 to 3.5 kW split system, a medium living area of 20 to 40 square metres a 5 to 7 kW unit, and a large open-plan space of 40 to 60 square metres a 7 to 9 kW system. These are indicative figures only. The correct capacity also depends on ceiling height, insulation, window size and aspect, and how the room is used, so the reliable way to size a system is an on-site assessment. Our on-site quotes are free.
Sizing is about matching the cooling and heating capacity of the unit, measured in kilowatts, to the heat load of the space. That load depends on floor area and ceiling height, how well the room is insulated, the size and orientation of its windows, how many people use it, and the local climate. Brisbane's warm, humid summers push the load higher than a cooler climate would. A proper calculation weighs all of these together rather than going off floor area alone.
Usually not. An oversized system cools the air quickly then shuts off before it has run long enough to pull humidity out, so the room can feel cold and clammy and the unit short-cycles on and off. That extra switching adds wear and can leave temperatures uneven. An undersized unit has the opposite problem, running flat out and struggling on the hottest days. The aim is the capacity that suits the space, which is why we size to the room rather than overselling capacity.
As a rough guide a standard bedroom of around 10 to 20 square metres is often served by a 2.5 to 3.5 kW split system. Larger bedrooms, high ceilings, or a west-facing wall with big windows can push that higher. Treat it as a starting point and confirm the exact capacity with an on-site assessment.
A medium living area of about 20 to 40 square metres is commonly matched to a 5 to 7 kW system, and a large open-plan living, kitchen and dining space of 40 to 60 square metres to roughly 7 to 9 kW. Open-plan layouts, high ceilings and large areas of glass all raise the requirement, so these ranges are indicative rather than fixed.
There is no single number for a whole home. A ducted system is sized around the combined load of the areas it serves, the layout and zoning, ceiling height, insulation and glazing. Zoning matters because you rarely condition every room at once, so the system is designed around how the home is actually used. We design ducted systems on site so the capacity and zones suit your home.
A phone or online estimate can get you in the right ballpark, but the accurate way to size a system is to see the space, because access, wall and window positions, ceiling height and insulation all affect the result. Coola Air Conditioning provides free, no-obligation on-site assessments across Brisbane's northern suburbs, and sizes each system to the space before quoting.
Get your air conditioner sized right
Tell us about your place and we'll assess the space, size the system correctly and send an upfront quote. Prefer to talk it through? Give us a call.
- Call us(07) 3543 2543
- Emailinfo@coolac.com.au
- Service areaNarangba to the Brisbane CBD