IPLV is an abbreviation for Integrated Part Load Value. Like the EER, the IPLV rating was developed by the Air-Conditioning and Refrigeration Institute. (In 1998, the ARI released a revised Standard, ARI 550/590-98 to cover IPLV.) Unlike the EER, however, the IPLV measures the efficiency of air conditioners under a variety of conditions — that is, when the unit is operating at 25%, 50%, 75% and 100% of capacity and at different temperatures.
IPLV is only calculated for non-residential central air conditioners — if you are purchasing a central air conditioning unit for your home, you should compare efficiency based on the SEER rather than the IPLV.