The Air-Conditioning, Heating and Refrigeration Institute (AHRI) has developed a standard (AHRI 550/590 Standard) that defines the Integrated Part Load Value (IPLV) as a better performance characteristic for chillers. Over the lifetime of a chiller, it is running at 100% capacity only 1% of the time, or in other words, 99% of the time it is at part load conditions.

The IPLV is calculated using the efficiency of the equipment while operating at capacities of:

• A = EER @ 100% Load
• B = EER @ 75% Load
• C = EER @ 50% Load
• D = EER @ 25% Load

The allocation of time running at these four loads defined by AHRI is as follows:

A=1%, B=42%, C=45% and D=12%

IPLV = 1%A + 42%B + 45%C + 12%D