A good energy efficiency ratio (EER) to aim for is 11, according to QualitySmith. Energy efficiency ratios are used to gauge the amount of energy the air conditioner uses in hot weather. A higher EER rating indicates that an air conditioner is able to help reduce energy costs.
Energy efficiency ratios are calculated by measuring how much energy an air conditioner uses when it is working to cool a house; this is implemented when the temperature outside is 95 degrees or higher, according to QualitySmith. The EER rating indicates how efficient an air conditioning unit is at keeping a house cool in a warm climate.