Power supply system and method for supplying power

The invention relates to a power supply system (26) for at least one electrical load (12), comprising at least one uninterruptible power supply (UPS) (14), a power output connection of the UPS (14) being connected to the at least one electrical load (12), at least one electrical energy storage means (28) and at least one switching means (32, 36), wherein - in a first mode of operation (48), a power input connection of the at least one UPS (14) and the at least one electrical energy storage means (28) are connected to a power mains (16) via the switching means (32, 36), - in a second mode of operation (52), the power input connection of the at least one UPS (14) is connected to the electrical energy storage means (28) via the switching means (32, 36). The invention further relates to a method for operating such a power supply system.