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Engineering ToolBox > Air Conditioner Efficiency
The 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, which shall be attached to all new air conditioners.
Some of the air conditioner manufacturers participate in the voluntary EnergyStar labeling program where EnergyStar-labeled appliances mean that they have high EER and SEER ratings.
EER is a measure of how efficiently a cooling system operates when the outdoor temperature is at a specific level (outdoor conditions commonly used 95? F). 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.
Select room air conditioners with EER of at least 9.0 for mild climates. In a hot climates, select air conditioners with EER over 10.
SEER - Seasonal Energy Efficiency Ratio - can be expressed as
SEER = Qc / P (1)
where
Qc = seasonal cooling energy (Btu)
P = seasonal power consumption (Watt-hours)
SEER should be at least 10 - and there are units with SEERs reaching nearly 17.
A cooling unit operating at 1 kW/ton 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 kW (1000 watts) per ton is equivalent to a COP of 3.516, or an EER of 12.