An instant hot water deliverysystem for efficiently heating water when necessary to provide instant hot water to a faucet. The instant hot water deliverysystem generally includes a water heater including an inlet and an outlet, a cold water supply line introducing cold water into the inlet, a hot water supply line connecting the outlet to a faucet and a recirculation line connected to the hot water supply downstream of the outlet and the cold water supply line upstream of the inlet. The recirculation line forms a first recirculation loop for water within the water heater to flow during a first water heating process. A recirculation pump is connected to the cold water supply line between the recirculation line and the inlet for circulating the water during the water heating process. In one embodiment, the control unit is used to retrofit an existing gas or electric water heater.
A water heater control for an electric water heater operates according to at least one fixed hardware and / or softwaretemperature limit and a variable softwaretemperature limit. The control monitors a temperature of water in a tank of the electric water heater to determine if the temperature exceeds the fixed hardware and / or softwaretemperature limit. If the temperature exceeds the fixed temperature limit, the control turns off one or more heating elements of the electric water heater. The variable software temperature limit is indicative of a desired user temperature and an offset temperature. If the temperature exceeds the variable software temperature limit, the control turns off the one or more heating elements.