While it is possible to plug a 100V FR-301 in a 120V outlet, a step-down transformer should be used. We do not recommend this however since these 100V units are designed for the Japanese domestic market. Connecting the units to 120V will cause an overvoltage on the PCB and the heating element that could lead to premature failure. The units are also not rated for safety to UL standards in North America. If a problem were to occur with the unit, you will need to return the unit to the place of purchase as we are unable to repair it.