# Air Conditioner Efficiency

## Air conditioner efficiency is the ratio between heat removed and power (watt) used - *EER* and *SEER*

Equipment used in cooling systems in residential and small commercial buildings often express the cooling system efficiency in terms like

*EER - Energy Efficiency Ratio and/or**SEER - Seasonal Energy Efficiency Ratio*

For air conditioners in rooms it is common to use *EER - Energy Efficiency Ratio*.

For central air conditioner systems it is more common to use *SEER - Seasonal Energy Efficiency Ratio.*

These ratings are normally 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 (35 ^{o}C)*).

- the higher
*EER*- the more energy efficient is the system

*EER* can be calculated

EER = q_{c}/ P (1)

where

q_{c}= output coolingenergy(Btu)

P = input electricalenergyconsumption (watt-hours, Wh)

*EER* is common for room air conditioners ranging *5000 -* *15000 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 above *10* should be selected.

Note that EER is sometimes based on cooling power and electrical power consumption as

*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 calculated

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 at least *17*.

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

_{power}

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

*12000 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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