There are provided an image forming apparatus which can implement on-demand fusing with quick rise in temperature by using the upper current (power) limit of a commercial power supply more effectively and a control method for the apparatus. This image forming apparatus includes a rechargeable battery device capable of charging and discharging, and is designed such that a load other than heating element of a fusing device can receive power from the commercial power supply and/or the rechargeable battery device. When printing is to be executed, the temperature of the fusing device is detected by a temperature detection element provided for the fusing device, and the supply of power from the commercial power supply or rechargeable battery device to the load is controlled in accordance with the detected temperature. The power supplied from the commercial power supply to the fusing device is then limited to a limit level corresponding to the control result.