There is provided an electric power control apparatus in an electric power system (11) with power sources connected thereto, the power sources including a generator, and a storage cell, including a power aggregator (4) for selecting the power sources on the basis of a CO2 origination amount. The power aggregator 4 includes a data collection unit (41) for receiving a selection condition of each of apparatuses collecting information via a setting screen on a display unit (46), thereby acquiring information including a voltage value, and a current value of each of the apparatuses in the electric power system, according to the selection condition, an electric power coloring unit (43) for computing of which power generator origin electric power stored in the storage cell is on the basis of the voltage value, the current value and admittance with respect to each of power sources, thereby computing a CO2 origination amount obtained by multiplying the electric power for every power generator origins by a CO2 emission coefficient preset by a power generation type, and a system control-apparatus computation unit (45) for displaying the CO2 origination amount by the power source on the display unit (46).