A display device includes a display panel including gate lines, data lines, and pixels connected to the gate lines and the data lines, a gate driver driving the gate lines, a data driver driving the data lines, a voltage generator generating first and second voltages to drive the gate driver, and a timing controller receiving an image signal, applying a data signal and first control signals to the data driver, and applying second control signals to the gate driver. The timing controller calculates a total operation time of the display panel and applies a first voltage control signal and a second voltage control signal to the voltage generator to correspondingly change a voltage level of at least one of the first and second voltages when the total operation time exceeds a predetermined reference time.