A demand response apparatus receives from a supply resource utilizing apparatus a signal indicating whether power supply from the demand response apparatus to the supply resource utilizing apparatus is possible, estimates a first power usage of the demand response apparatus for a first time interval, changes an operation of the demand response apparatus, estimates a second power usage for a second time interval after the changing of the operation of the demand response apparatus, calculates supply power available to the supply resource utilizing apparatus based on the estimated first power usage and the estimated second power usage, and transmits information about the available supply power to the supply resource utilizing apparatus.