Disclosed embodiments relate to a power monitoring system. In some embodiments, the power monitoring system includes: a sampling device configured to measure patterns of how loads included in the power system consume energy; an electric meter configured to measure a first amount of energy supplied from a transmission system to the power system; a power supply configured to supply power stored therein or generate power to supply it to the power system, and measure a second amount of energy supplied to the power system; an external server configured to receive measurements of the patterns from the sampling device, and obtain a third amount of energy consumed by the loads based on the measurements; and a home server configured to receive the first amount of energy and/or second amount of energy and transmit/receive data to/from the external server.