Comparative performance analysis of fixed or oriented (single axis or twin axis type) sun tracking systems in the field requires that the solar PV arrays mounted on the test tracker and the reference tracker, not only have to be identical, but also tested under identical operating conditions. In order to satisfy the above criteria as well as to extract the maximum output, the identical operating condition for a comparison test is chosen to be the maximum power point operation. Use of an electronic load, realized with a MOSFET serving as a variable load resistor, in conjunction with a microcontroller for maximum power point operation of a PV array during such comparative tests is presented in this paper. A prototype measurement system based on the proffered technique is developed to carryout comparison studies on sun tracker systems in the filed. Using the prototype, tests were conduced to compare the performances of a fixed PV array system and a two step, stepwise manual tracker. Simulation results and experimental results obtained using a prototype unit built and tested establish the efficacy of the proposed technique for proper comparison of sun tracking systems, in the field. © 2013 IEEE.