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Choosing a system

Sizes, ratings, noise and features, and the questions worth asking.

11 guides · about 38 minutes of reading

  1. 01What size air conditioner do you need?Most bedrooms and smaller living rooms suit a unit of about 2.0 to 3.5 kW, and large open-plan spaces often need 5.0 kW or more. Sun, glazing, insulation and ceiling height can matter as much as floor area.4 min read
  2. 02kW and BTU explainedkW and BTU per hour both measure an air conditioner's capacity, meaning how much heat it can move. One kW is about 3,412 BTU per hour, so a 3.5 kW unit is roughly a 12,000 BTU unit.3 min read
  3. 03Energy labels: SEER and SCOP explainedSEER and SCOP are the seasonal efficiency ratings on an air conditioner's energy label, for cooling and heating. Each shows roughly how much heat the unit moves over a standard season for every unit of electricity it uses, and higher is better.3 min read
  4. 04How loud is air conditioning?Quiet indoor units are often around 19–26 dB(A) on their lowest fan speed and louder at higher speeds, while outdoor units are typically 45–50 dB(A) at 1 metre. How loud it seems also depends on where the units are and how hard they're working.4 min read
  5. 05Decibels explainedA decibel (dB) is a unit on a logarithmic scale, so adding 10 dB means ten times the sound energy and sounds roughly twice as loud. Air conditioner figures are usually in dB(A), which reflects how sensitive hearing is to different pitches.4 min read
  6. 06Features worth havingThe features that make the most day-to-day difference are an inverter, heating that copes with cold weather, a genuinely quiet lowest fan speed, good airflow control, useful timers and easy-to-clean filters. Many extras are pleasant rather than essential.3 min read
  7. 07What air conditioning filters doAir conditioning filters catch dust and fibres before they reach the indoor unit's coil and fan, keeping air flowing freely and the inside of the unit cleaner. Most are washable mesh screens that need cleaning every few weeks in regular use.3 min read
  8. 08Wi-Fi, apps and smart controlsMany air conditioners can be controlled from a phone app over your home Wi-Fi, either built in or through an add-on adapter. An app lets you switch on, change settings and set schedules from anywhere, while the remote usually still works as normal.3 min read
  9. 09Which rooms benefit mostBedrooms usually benefit most, because heat makes sleeping hard, followed by top-floor and loft rooms, home offices and sunny living spaces. The best candidates are rooms you use a lot that regularly overheat, rather than every room in the house.3 min read
  10. 10Where to put the indoor unitA wall-mounted indoor unit usually goes high on a wall with clear space around it, where its airflow can reach the whole room without blowing straight at people. The best spot also depends on the route for the pipes and where the condensate can drain.4 min read
  11. 11Questions to ask an installerAsk how they sized the system, where both units and the pipes will go, whether it meets planning and noise rules, what the quote includes, which F-gas and electrical qualifications they hold, and what warranty and servicing come with it.4 min read