The aim of this paper is to compare two high power devices namely CoolMOS and MOSFET in high frequency basic inverter circuit. Where inverter can be used in UPS system, obtaining high quality and efficient AC output at the load requires proper selection of driving power switches. Even though MOSFET has already known for its superior in high frequency operation and high power applications, CoolMOS power device could produce better results in lowering total switching loss in the inverter. The study also looks into the comparison of power losses in the output load from switching activity of both devices during their operating cycles. From the experiment, it can be seen that CoolMOS device can produce higher power saving by at least 82 compared to its counterpart, MOSFET. © 2008 IEEE.