Modular control system and method for water heaters

A water heater having a modular control system, comprising:

• a tank;
• a heating element coupled to the tank;
• a first controller mounted on the tank, the first controller including a first base, first control logic, and a first communication port for coupling the first controller to another controller, wherein the first communication port and the first control logic are mounted on the first base, the first control logic configured to
• determine whether the first communication port is conductively coupled to another controller, and
• control the heating element using at least one first set point in accordance with a first algorithm if the first communication port is not conductively coupled to another controller;
• and
• a second controller mounted on the tank, the second controller including a second base, a second control logic, and a second communication port that is selectively connectable to the first communication port of the first controller, wherein the second communication port and the second control logic are mounted on the second base, the second control logic configured to
• control the heating element in accordance with a second algorithm, and
• automatically determine at least one second set point for controlling the heating element according to the second algorithm,
• wherein the first controller is further configured to allow the second controller to control the heating element when the second controller is conductively coupled to the first communication port, wherein the first controller is unable to control the heating element in accordance with the second algorithm in an absence of the second controller, wherein the heating element is connected to the first controller, and wherein the second controller operates the heating element through the first controller.