A class E power amplifier is demonstrated for application to a wireless power transfer system. The amplifier consists of input matching circuits, a RF power transistor as a switching device, and a load network with a lumped element matching circuit. The discrete components in the load network are designed with parallel circuit to reduce the efficiency degradation due to the parasitic resistance and characteristic variation. The single-ended amplifier with 20 V supply voltage shows 21.7 W output power and 81.6% power added efficiency at 6.78 MHz.