A first estimator estimates first power to be generated by a photovoltaic power generation apparatus during an interested period. A second estimator estimates second power to be consumed by an electric load during the interested period. A power purchasing cost calculator calculates, when there is a shortfall in the first power compared to the second power, a cost to be paid for receiving, from a power grid, power for compensating for the shortfall. A determiner compares an amount of money to be paid to a customer facility in accordance with a trading term when power is supplied from the power storage apparatus to the power grid, with the cost calculated by the power purchasing cost calculator. A controller causes the power storage apparatus to the electric load when the cost to be paid to the customer facility is equal to or less than the cost.