Apparatus includes a main body having a function of reducing performance of the apparatus during operation, an AC adapter which is connectable to the main body and supplies power to the main body from a commercial power source, and a rechargeable battery which is connectable to the main body and discharges to supply power to the main body. Apparatus operates without reducing the performance even while the power supplied from the AC adapter is turned off and the power is supplied from the battery during a peak shift period (e.g. mid-day summer where limiting the power supplied by the AC adapter is desirable) in a state where both the AC adapter and the battery are connected to the main body, and thereafter, the power supplied from the AC adapter is turned on and power is supplied to the main body from the AC adapter even during the peak shift period.