The current invention relates to an uninterruptible power supply (UPS) with PeakShaving and energy time shifting functions system comprising at least one UPS comprising an AC/DC conversion stage, a DC/AC conversion stage, and at least one Energy Storage System (ESS); an Energy Management System (EMS) configured to control the system: at least one processor, and at least one non-transitory computer readable media comprising software; wherein the software causes the processor to configure the system to operate according to different operating stages.