What Size Air Conditioner Do I Need?
Choosing the right size split system is one of the most important parts of getting comfortable, efficient cooling and heating in your home.
Quick Air Conditioner Size Guide
As a general guide, you can allow approximately 1kW of cooling capacity for every 10–15m² of room space. These recommendations are a guide only and may vary depending on your home.
For approximately every 10–15m² of room space, depending on insulation, windows, ceiling height and sun exposure.
| Room Size | Recommended Capacity | Typical Use |
|---|---|---|
| Up to 15m² | 1.5kW – 2.0kW | Small bedrooms, guest rooms and small offices |
| 15m² – 25m² | 2.5kW – 3.5kW | Bedrooms, master bedrooms and home offices |
| 25m² – 40m² | 4.0kW – 5.5kW | Small living rooms and medium rooms |
| 40m² – 60m² | 6.0kW – 7.1kW | Large living areas and family rooms |
| 60m²+ | 8.0kW – 9.5kW | Open-plan living, dining and kitchen areas |
Air Conditioner Size by Room Type
Bedrooms
2.0kW – 2.5kWLarger master bedrooms, sun-exposed rooms or bedrooms with large windows may require a 3.5kW system.
Home Offices
2.0kW – 3.5kWConsider room size, sun exposure and heat generated by computers, screens and office equipment.
Living Rooms
5.0kW – 6.0kWIf the room is open to a kitchen, dining area or hallway, a larger system may be required.
Large Living Areas
6.0kW – 7.1kWDesigned to move more air and maintain comfort across larger spaces.
Open Plan Areas
7.1kW – 9.5kWBest for open-plan living, dining and kitchen areas depending on total size and layout.
High Heat Rooms
Size may increaseRooms with large west-facing windows, poor insulation or strong afternoon sun may need additional capacity.
Why Correct Sizing Matters
Choosing the correct size air conditioner affects comfort, efficiency, running costs and system lifespan.
If the system is too small
- It may run constantly
- It may struggle on very hot days
- It may take longer to cool or heat the room
- It may use more power trying to keep up
- It may reduce the lifespan of the system
If the system is too large
- It may cycle on and off too often
- It may not remove humidity effectively
- It may feel less comfortable
- It may cost more upfront
- It may use more power than needed
Factors That Affect Air Conditioner Sizing
Ceiling Height
High ceilings increase the total air volume, which may require a larger system.
Windows & Glass
Large windows and sliding doors can let in significant heat during summer.
Sun Exposure
West-facing rooms and afternoon sun can increase cooling requirements.
Insulation
Well-insulated homes hold temperature better and reduce system load.
Open Layouts
Open-plan spaces are harder to cool than enclosed rooms.
Room Use
Kitchens and home offices may generate extra heat from appliances and equipment.
Perth Climate Considerations
Perth summers can be extremely hot, so it is important to choose a system that performs well during peak heat. Homes with poor insulation, large west-facing windows, dark roofing or open-plan layouts may need additional capacity.
Common Size Examples
2.0kW
Best for small bedrooms, guest rooms and small home offices.
2.5kW
Best for standard bedrooms, children’s rooms and small master bedrooms.
3.5kW
Best for large bedrooms, home offices and small living areas.
5.0kW
Best for living rooms, medium family rooms and larger enclosed spaces.
7.1kW
Best for large living rooms, open-plan areas, dining and kitchen spaces.
8.0kW – 9.5kW
Best for large open-plan homes, high ceilings or high heat-load spaces.
Should I Size Up?
Sometimes, yes. However, bigger is not always better. Oversizing can reduce efficiency and comfort, so the best option is to size based on the full room conditions.
- Large west-facing windows
- Poor insulation
- High ceilings
- Lots of direct sunlight
- Open adjoining areas
- Kitchen appliances nearby
- Dark roofing or high heat gain
Need Help Choosing the Right Size?
Every home is different. If you're unsure what size split system you need, contact the BESS Air team via live chat or request a Site Inspection & Custom Quote.