A water heating system includes a tank, one or more heating elements mounted on the water heating system, and a first controller mounted on the tank. The first controller is coupled to the one or more heating elements and includes logic to activate and deactivate the heating elements according to a first threshold value. The water heater also includes a second controller that is selectively coupled to the first controller and configured to communicate the first threshold value to the first controller, and perform an additional function related to the operation of the water heater. The first controller is configured to receive the first threshold value from the second controller and control the one or more heating elements based on the received threshold value, and to control the one or more heating elements mounted on the water heating system in a physical absence of the second controller.