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# Conversion Between EER, SEER, IEER

## Conversion Between EER, SEER, IEER

(OP)
Hi All,

I'm seeking a method for converting between EER, SEER, & IEER. I require this information each time I file drawings and have grown tired of waiting for Sales Engineers to get back me with these numbers.

Any information will help.

Thanks.

### RE: Conversion Between EER, SEER, IEER

The problem "converting" between EER and SEER is that they don't measure the exact same thing.  It's not like measuring a heat loss and converting between BTU/hr and kW.

As you probably know, EER is an efficiency rating measuring cooling in BTU/hr compared to electrical energy input in kW.  It is calculated based on one single set of conditions for the indoor and the outdoor space.

SEER numbers are based on a range of outdoor air temperatures to try and predict the ratio of cooling to input power annually.

Because of this it isn't always a linear relationship and different climates begin to throw off any empirical relationships between EER and SEER.  The US DOE has provided this acceptable correlation however:  EER = –0.02 × SEER² + 1.12 × SEER

Just note that this is really only a quick and dirty correlation.

### RE: Conversion Between EER, SEER, IEER

PS, a followup to the post I just made.  I realized I didn't address IEER.

Essentially you have the same problem "converting" between IEER and EER as you do EER and SEER. They don't measure the same thing Because IEER is a weighted average, you need the EER rating at 4 different load points (which you don't always have) to calculate IEER.  If  you DO have the EER at 100%, 75%, 50%, and 25% full cooling capacity, the IEER can be calculated by:

IEER = (0.020 * A) + (0.617 * B) + (0.238 * C) + (0.125 * D)

Where:
A = EER at 100% net capacity at AHRI standard rating conditions
B = EER at 75% net capacity and reduced ambient (81.5oF for air-cooled)
C = EER at 50% net capacity and reduced ambient (68oF for air-cooled)
D = EER at 25% net capacity and reduced ambient (65oF for air-cooled)

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