Power switching devices based on wide bandgap semiconductor materials, such as silicon carbide (SiC) and gallium nitride (GaN) offer superior performance such as low switching and conduction losses, high voltage, high frequency, and high temperature operation. In this paper, a 600-V GaN switch and a 600-V GaN diode were tested in detail to understand the GaN device capabilities with respect to equivalent silicon-based devices such as IGBT and MOSFET. Detailed experimental loss models are developed and compared with datasheet models. Experimental setup of different power converters such as boost, buck–boost, and half-bridge inverter and associated comparative experimental results are presented. This paper also presents the investigations into the effectiveness of using GaN devices and higher switching frequencies in reducing the total size and cost of power conversion equipment such as an online UPS system.