A screen saver controller includes a temperature calculator, a temperature comparator, an operator, and a screen saver data generator. The temperature calculator calculates temperature data of a display panel based on input image data. The temperature comparator receives the temperature data and a target temperature and compares a temperature of the display panel with the target temperature to generate temperature change data. The operator receives the temperature data and the temperature change data and generates operation data based on the temperature data and the temperature change data. The screen saver data generator receives the operation data and generates screen saver data based on the operation data. The screen saver controller adjusts a luminance of the display panel based on the screen saver data when operating in a first mode.