A control system for a water heater generally includes a water heater controller configured to receive upper and lower sensor temperatures associated with water in the respective upper and lower portions of the tank. The water heater controller is configured to determine a value indicative of a portion of water in the tank at a desired set-point temperature as a function of the upper sensor temperature, the lower sensor temperature, and the desired set-point temperature. The water heater controller is configured to wirelessly transmit at least one signal indicative of said value indicative of the portion of water in the tank at the desired set-point temperature. A user interface includes a plurality of selectively illuminated segmented portions. The user interface is configured to receive said value from the water heater controller and to selectively illuminate a number of segmented portions representative of said value.