# Air Conditioner Efficiency

##
The ratio between heat removed - to watt of power used - *EER* and *SEER*

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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 ^{o}F*).

- The higher
*EER*the more energy efficient system.

*EER* can be expressed as

EER = q_{c}/ p (1)

where

q_{c}= 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 = Q_{c}/ P (2)

where

Q_{c}= 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 per hour* 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*.

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