This invention consists of an apparatus to interface an electric vehicle battery with a solar photovoltaic system and a method of using the apparatus to provide back up power during grid outages and ancillary service revenue from the grid. The apparatus uses the solar PV inverter to provide bidirectional power flow from the battery during night-time hours, or whenever the solar array is producing insufficient power. The apparatus thus consists only of switches and control and measurement equipment. It relies on the otherwise underutilized inverter and the on-board vehicle battery charger as the power electronic components, thus minimizing cost.