Performance evaluation of a high-resolution computer based efficiency measurement system for electric vehicle (EV) traction inverter is given. First, a simulation study is carried out to determine the upper limit of the EV traction inverter efficiency curve. Then, experimental efficiency measurements are completed. In the experimental study, a 30kVA induction machine-dynamometer system is used to obtain the loading between 1kW-8kW. Efficiency measurements are completed with both the YOKOGAWA WT500 power analyzer and the proposed computer based efficiency measurement system. Results are discussed and compared considering the accuracy and the cost.