The purpose of this paper is to quantitatively compare the efficiency, of silicon and silicon carbide power devices in power circuit environments. Models developed for the MOSFET, PiN rectifier, Schottky rectifier, for both silicon and silicon carbide will be presented. These models have been implemented in the SABER circuit simulator and used to simulate power circuits, in order to determine the efficiency of the silicon and silicon carbide devices. It is essential for a fair comparison that the two devices are optimally designed, hence optimization of area has been performed and an analytical expression, for the optimum area as a function of operating conditions, determined. The efficiency for the optimum silicon and silicon carbide devices as a function of frequency, blocking voltages and operating currents is then presented. It has been shown that the 5000V SiC MOSFET has efficiencies comparable to the 300V Si counterpart.