PV water heating system

A hot water heating system, comprising:

• a storage tank having:
• an inlet fluidly connectable to a water supply;
• an outlet fluidly connectable to at least at least one valve, wherein when the valve is opened, water from the water supply displaces water through the storage tank and out the outlet;
• a first heating element connectable to a power source that provides one of combustible gas and AC electricity;
• a thermostat interconnected to the first heating element, wherein the thermostat controls operation of the heating element based at least in part on a temperature of water in the storage tank;
• a second heating element, having:
• a threaded collar for threaded insertion with a threaded opening of the storage tank,
• an electrical heating element connected to the threaded collar, wherein the electrical element is disposed within the storage tank when the threaded collar is threaded into the threaded opening of the storage tank;
• an electrical connector electrically connected to the electrical element, wherein the electrical connector is disposed on an outside of the storage tank when the threaded collar is threaded into the threaded opening the storage tank;
• a renewable DC power source having electrical leads interconnected to the electrical connector, wherein the renewable DC power source provides electrical power to the second heating element
• a controller interconnected to the first heating, element and the second heating element, wherein the controller selectively operates the first and second heating elements, wherein the controller further comprises:
• operating logic adapted to identify expected usage times when water passes through the tank between the inlet and the outlet;
• and
• control logic operative to control the first and second heating elements based at least in part on the usage times.