Air Conditioner Efficiency Air conditioner efficiency express the ratio between heat removed to watt of power used - EER and SEER Sponsored Links
Cooling equipment systems used in residential and small commercial buildings often express cooling system efficiency in terms of the Energy Efficiency Ratio - EER - and/or Seasonal Energy Efficiency Ratio - SEER. For room air conditioners the commonly used efficiency ratio is the EER - Energy Efficiency Ratio For central air conditioners the commonly used ratio is SEER - Seasonal Energy Efficiency Ratio These ratings are posted on the Energy Guide Label attached to all new air conditioners. Some air conditioner manufacturers participates in the voluntary Energy Star labeling program where the Energy Star label indicates higher EER and SEER ratings.
EER - Energy Efficiency Ratio EER is a measure of how efficiently a cooling system operates when the outdoor temperature is at a specific level (outdoor conditions commonly used are 95 oF). 
The higher EER the more energy efficient system.
EER can be expressed as EER = qc / p
(1)
where qc = cooling energy (Btu/hr) p = power consumption (Watts)
EER is commonly used for room air conditioners ranging 5,000 Btu per hour to 15,000 Btu per hour. 
1 Btu/h = 2.931x10-4 kW = 0.0299 kpm/s = 0.252 kcal/h = 3.986x10-4 hk = 3.939x10-4 hp = 0.2163 ft lb/s
In mild climates air conditioners with EER of at least 9.0 should be selected. In hotter climates air conditioners with EER over 10.should be selected.
SEER - Seasonal Energy Efficiency Ratio SEER - Seasonal Energy Efficiency Ratio - can be expressed as SEER = Qc / P
(2)
where Qc = seasonal cooling energy (Btu) P = seasonal power consumption (Watt-hours) SEER should be at least 10 - there are units where SEER reach ate least 17.
Example - EER A cooling unit operating at 1 ton/kW would have an EER of 12,000 Btu divided by 1000 watts or 12. This is mathematically equivalent to multiplying the COP by 3.413. Therefore a small cooling unit operating at 1 ton per kW (1000 watts) is equivalent to a COP of 3.516, or an EER of 12.