# 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 efficient a cooling system operates in steady state (over time) 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}= output coolingenergy(Btu)

P = input electricalenergyconsumption (watt-hours, Wh)

*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.

Note that EER is sometimes expressed with cooling power and electrical power consumption

*EER _{power} = q_{c} / P (1b)_{}*

*where *

*q _{c} = output cooling power (Btu/h)*

*P = input electrical power consumption (W)*

### SEER - Seasonal Energy Efficiency Ratio

SEER - Seasonal Energy Efficiency Ratio - can be expressed as

SEER = Q_{c}/ P (2)

where

Q_{c}= seasonal coolingenergy(Btu)

P = seasonal electricalenergyconsumption (Wh)

*SEER* should be at least *10* - there are units where SEER reach ate least *17*.

### Example - *EER*_{power}

_{power}

A cooling unit operating at *1 ton/kW* would have an *EER _{power}* 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

_{power}*12*.

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