Room Air Conditioners

A room air conditioner (RAC) cools the air, removes humidity, circulates air, filters out dust, and in some cases also provides heating. Although most RACs are designed for the residential market, about 20 percent of commercial buildings are cooled by them as well. Building operators and managers purchase RACs for one of several reasons:

  • They want to cool selected rooms in an otherwise uncooled building.
  • It isn't feasible to install central cooling in their building.
  • They want to completely isolate one room from another (to avoid mixing air between rooms, so that each room has complete controls autonomy, so that each room can be billed separately, or all of the above).
  • They want to replace a failed RAC.

Commercial and industrial RAC consumers often waste money by not paying attention to efficiency ratings. New RACs in the U.S. range from about $200 to over $1,000 and have energy efficiency ratios (EER) that range from 8.0 to 12. More efficient units are often more expensive than less efficient units, but not always. Smart consumers can save money in the long run by accounting for both first cost and operating cost, and then selecting the unit with the lowest lifecycle cost.

Air-conditioning terms

Here are some terms you may encounter as you're comparing models.

Capacity indicates the amount of cooling a unit can produce and is expressed in British thermal units per hour (Btu/h) or in kilowatts (kW). Models on the North American market range from 4,200 to 35,000 Btu per hour.

Efficiency in the U.S. and Canada is designated by an energy efficiency ratio (EER), which is calculated by dividing Btu per hour (the measured cooling capacity) by watts (electricity input).

Coefficient of performance, another measure of efficiency used in some nations, is the ratio of the rate of heat removal to the rate of energy input.

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