What size air conditioner do I need for my room?

Start with the room, not a universal formula

Floor area is useful for screening the likely range, but rooms with the same floor area can have very different loads. A final recommendation should also consider:

• ceiling height and room volume;
• roof, ceiling and wall insulation;
• window area, glass, curtains and external shading;
• orientation, especially exposed western sun;
• upstairs rooms and heat beneath the roof;
• occupancy and heat from kitchens or equipment; and
• doorways, adjoining spaces and where air can realistically travel.

Compare models at the capacity the room requires

The 2.5, 3.5, 5 and 7 kW figures commonly seen in stores describe heating or cooling output. They are not universal room-size codes. Once the likely load is known, compare systems with similar output, relevant efficiency information and appropriate indoor and outdoor sound levels.

An undersized system may run hard without bringing the room under control. Deliberately choosing the next size up is not a reliable shortcut either: a larger unit costs more and still cannot push air effectively into separated rooms.

For a final recommendation, send the room dimensions, ceiling height, suburb and wide photos of the room and possible outdoor position. Start with our Perth air-conditioning installation guide, then see the split-system air-conditioning service for the complete assessment and installation process.