Disclosed embodiments relate to a power monitoring system. In some embodiments, the power monitoring system includes: a sampling device configured to measure patterns of energy consumed by loads included in the power system; an electric meter configured to measure an amount of second energy supplied from a system to the power system; a power supply configured to supply power stored therein or generate power to supply the power system and measure an amount of third energy supplied; and an external server configured to receive at least one of the patterns, the amount of the second energy and the amount of the third energy and analyze the patterns to acquire an amount of first energy for each of the loads. In some embodiments, the external server calculates at least one of the amount of the first, second and third energy.