Buying Guide: Air Conditioning

Find the suitable air conditioner for your home with this buying guide taking you through the basics of the different types of air conditioners, including the split system, window/wall or mobile (movable) units.

Room Size Vs. Air Conditioner Capacity

Reverse cycle split system air conditioner

Match the air conditioning unit to the size of the room it's cooling. As a rule of thumb, the bigger the room, the more powerful an air con unit will have to be to cool it:

  • Underpowered air conditioners will have to work harder, wasting energy
  • Overpowered air conditioners are an unnecessary expense

How Much Capacity Will I Need?

Air conditioners are rated by BTU (British Thermal Unit) and power output, in kilowatts (kW). To work out the approximate sized air con you'll need, apply this simple formula:

  • Bedroom: 80 watts (0.080kW) per square metre (length by width). For example, a 16m² bedroom should need around 1.28kW of air conditioning
  • Living room: 125 watts (0.125kW) per square metre. For example, a 30m² living room should require around 3.75kW

Proximity to the kitchen and appliances increases a room's required cooling.

Which Type Of Air Conditioner?

Ducted: Cool multiple rooms through a large cooling fan, which sits outside and pumps cool air around the building through ducts, which are housed in the ceiling cavity.

Window units: Mounted through a window/wall. These are excellent for small rooms.

Split system: The cooling unit is installed outside, with the fans mounted inside. A split system air conditioner is suited to cooling one or more adjoining rooms.

Multi-split system: Utilising one outdoor unit, with multiple fan units inside to distribute the cool air throughout the house.

Reverse cycle split system air conditionerPortable: Small, light and mobile, so they're movable from room to room. Portable units have a low power output, suited to small spaces –- apartments and renters. 

Evaporative coolers: Appear like cheaper versions of portable air conditioners, but do not use refrigerant technology. They work by drawing air past a special water-cooled 

filter system.

Technical Terms You Should Know

  • Reverse cycle: The reverse cycle air conditioner internally reverses its operation to provide heating or cooling, as required
  • Inverter system: Constantly alters fan and motor speeds. This enables faster cooling of a room, and the inverter air conditioner doesn't have to switch itself on and off to maintain a constant temperature

Energy Efficiency

The Australian Government recently introduced changes to the energy rating system. Energy efficiency is now rated out of 10 stars, rather than the previous six-star system.

  • Air conditioning star rating stickers now display cooling and heating efficiency side by side
  • This replaces the old six-star rating sticker, which displayed cooling as a blue crown on top of the red heating crown
  • Manufacturers of inverter systems claim that they are 30 per cent more efficient during partial load

Noise Issues

If you're considering an outdoor air conditioning unit, make sure to check the relevant noise level regulations.

Are Filters Necessary?

Yes. Good air conditioning units will use filters to prevent bacteria and allergens being recycled through the room. Filters require cleaning every few weeks to ensure the remain effective, and some units will also indicate when the filters need changing.

Positioning Is Important

Portable air conditioner

  • Avoid positioning the air conditioning unit on the side of the house that gets the most sun as this will cause it to be less efficient
  • For efficient cooling, mount the unit high in the room — allowing the cool air to sink


Do not attempt to install a split or ducted system without holding the appropriate licenses, this will also void your warranty.