Air conditioning units are available in a variety of sizes with multiple efficiencies at each size range. The efficiency of these units is a function of the size of the heat transfer surfaces, the efficiency of the compressor and fan motors, and the operating parameters. The higher the SEER (Seasonal Energy Efficient Ratio) or EER (Energy Efficient Ratio), the more efficient the air conditioner.
Currently, unitary air conditioning units (65 to 250 MBH) sold in Canada are regulated by Canada's Energy Efficiency Regulations. Natural Resources Canada is in the process of changing the minimum efficiency requirements for units imported or shipped interprovincially for sale in Canada. The new minimum efficiencies will regulate single package and split system air conditioning units with rated capacity of <65 MBH, as well as factory assembled commercial unitary units with capacity from 65 to 240 MBH.