An image forming apparatus having a thermal fixing unit reduces a current inputted from a commercial power source using electric power charged in the capacitive when warming up the thermal fixing unit. The apparatus comprises a first charging unit to charge the capacitive unit at a first charging rate, and a second charging unit to charge the capacitive unit at a second charging rate lower than the first charging rate and greater than a natural power discharge rate of the capacitive unit. A charge switching control unit switches a power source charging the capacitive unit from the first charging unit to the second charging unit when the image forming apparatus transitions into an energy saving standby mode, and returns the power source charging the capacitive unit from the second charging unit to the first charging unit when the image forming apparatus returns from the energy saving standby mode.