An electric power control apparatus outputs output from a power generation apparatus to a power system has a power converter that converts power output from the power generation apparatus and a power storage apparatus that stores output from the power generation apparatus or output from the power converter as well as discharges stored electric power as necessary detects an amount of electric power generated at the power generation apparatus within a predetermined time period, sets an output pattern of the electric power control apparatus in a next predetermined time period based on the amount of electric power of each predetermined time period, and controls the output of the electric power control apparatus in accordance with the output pattern. By so doing, for example, even where the output from the power generation apparatus fluctuates, the amount of electric power output to the power system is decided in advance, and electric power equivalent to the difference between the predetermined amount and the output amount is stored in a power storage apparatus or discharged from the power storage apparatus.