Abstract: This invention provides a system and process to optimize photovoltaic (PV), grid, and other electricity in powering an electric water heater. The system comprises a photovoltaic (PV) controller coupled to a plurality of power input sources and heating elements wherein the heating elements immersed in an electric immersion heater water tank. The PV controller is further configured with control circuitry having an operating efficiency routine calculating optimal use cases from a variety of installation parameters and learned parameters to determine the appropriate power input source and switch between sources accordingly.