A system and a method for electricity management are disclosed. The system includes a data management unit, a cabinet, a control unit, an uninterruptible power supply apparatus and a power switch. The cabinet is powered by an external power supply. When the data management unit sends a testing instruction to the cabinet, the control unit controls the power switch to shut down the external power supply such that the cabinet is powered by the uninterruptible power supply apparatus instead. The control unit measures a set of battery parameters of the uninterruptible power supply apparatus, computes a power supply capacity of the uninterruptible power supply apparatus according to the set of battery parameters, and returns the power supply capacity to the data management unit.