An uninterruptible power supply includes a battery unit including battery racks divided into at least one first battery rack including a first battery and at least one second battery rack including a second battery; an overall control unit configured to determine an operation mode of the battery unit from among a discharge mode and a charge mode, and a measurement unit configured to monitor an amount of accumulated power consumption of the load during each of a plurality of time periods and transmitting data associated with the monitoring to the overall control unit.