Recent advancements in modem electronics have made it possible to collect the various "transient noise" signals that are present on electric power lines of motordriven equipment while using a simple non-intrusive, clamp-on inductive pickup. Electronic filters are used to analyze the noise signal with an on-the-spot, real-time analysis. An exploratory study, conducted at a national laborato~ examined the potential for using the motor current signature on heat pumps and air conditioners as a diagnostic tool Preliminary results show that there is some correlation between the motor current signature and the performance of a heat pump. However, tests and associated analysis were limited, and additional research is needed to determine the full potential of motor current signature analysis (MCSA).