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Choosing the Right Cooling Capacity for your Air-conditioner

Air-conditioners are designed to control both the air temperature and humidity. Choosing the right cooling capacity for your air-conditioner is important for proper comfort and to save energy.

An oversized air-conditioning system is costly and may cost more to operate. It might also not properly dehumidify the space. This is because the air-conditioner cools the space too quickly and then powers down before the moisture level is reduced. On the other hand, an undersized air-conditioning system will not provide adequate cooling and dehumidification.

To size your air conditioning system, a useful rule of thumb is to divide the area of the space to be air-conditioned by 5, i.e.:

Cooling capacity required in kW = Total area to be air-conditioned [m2] ÷ 5

*to convert to Btu/hr, multiply the kW result by 3412
* to convert from ft
2 to m2, multiply the area in ft2 by 0.093 

Points to note:

  1. A larger air-conditioner may be needed for rooms with:
    •  Double volume (i.e. double ceiling height)

    • A large window area (e.g. full-height glass windows)

    • Windows orientated towards the sun (i.e. east-west direction)

    • Additional heat sources such as bar fridges

  2. Total cooling capacity of a multi-split air-conditioner is usually the sum of the cooling capacities of the individual rooms. However, a smaller total cooling capacity may be sufficient if all the room units are not turned on at the same time.
  3. For a more detailed assessment of the cooling capacity required, please consult your air-conditioner supplier.

We thank Carrier, Daikin, LG, Mitsubishi Electric and Panasonic for their inputs in the development of this air-con cooling capacity guideline.

Last Updated on : 11 February 2016
© 2012 National Environment Agency