A power management apparatus is provided. The apparatus includes a communication unit configured to receive information on a price of power and communicate with image forming apparatuses, and a control unit configured to control image forming apparatuses to operate at a normal mode and/or a power saving mode by comparing the information received on the price of power with information on a standard price of power. A user may conduct a printing at a desired time to minimize inconvenience. A mode of the power management apparatus is determined according to the price of power such that a plurality of image forming apparatuses are operated at a normal mode when the price of power is low, and at least one image forming apparatuses is operated at a normal mode when the price of power is high, thereby reducing cost and enhancing the efficiency in managing the power.