IPLV

IPLV stands for Integrated Part-Load Value — a weighted-average efficiency rating that represents how a chiller performs across a realistic load profile rather than at a single full-load design condition. AHRI Standard 550/590 defines the IPLV calculation: efficiency is measured at 100%, 75%, 50%, and 25% load, then weighted by the percentage of hours commercial chillers typically operate at each level (1%, 42%, 45%, and 12% respectively).

For most commercial buildings, IPLV is a better predictor of annual electricity cost than full-load EER, because chillers spend less than 5% of their operating hours at full load. A unit with an EER of 14 at full load but an IPLV of 0.65 kW/ton at typical loading will cost more to operate annually than a unit with EER 12 at full load but IPLV of 0.45 kW/ton.

Magnetic-bearing variable-speed chillers excel on IPLV because their oil-free, frictionless compressor design maintains high efficiency at low loads. Fixed-speed and standard variable-speed units lose efficiency rapidly below 50% load. When comparing financing options on units that have similar headline EER ratings, ask the distributor for the IPLV — the unit with the better IPLV will produce a meaningfully better ROI over the financing term.