A power reserve margin trading system comprising: a first acquisition unit configured to acquire a predicted power demand amount and a power reducible amount for a predetermined period in the future for each customer; a reserve margin trading unit configured to trade the power reducible amount of the customer acquired by the first acquisition unit as a reserve margin for demand adjustment and thereby to acquire a consideration; a second acquisition unit configured to acquire a power consumption amount for each customer; a determination unit configured to calculate, for each customer, a difference between the predicted power demand amount acquired by the first acquisition unit and the power consumption amount for the predetermined period acquired by the second acquisition unit, and to determine a rank of each customer by giving a higher rank to a customer having a smaller value of the calculated difference; a notification unit configured to determine a reduction request amount for each customer based on the power reducible amount acquired by the first acquisition unit and to transmit the reduction request amount to the customer as notification when a power reduction request is sent; an estimated reduction amount calculation unit configured to calculate, for each customer, an estimated reduction amount being an estimated reduction amount of power consumption by use of the predicted power demand amount acquired by the first acquisition unit and a power consumption amount after the reduction request amount transmission calculated by using the power consumption amount acquired by the second acquisition unit; and a trading consideration distribution unit configured to distribute a consideration acquired by the reserve margin trading unit into customers in such a manner that a customer determined as a higher rank by the determination unit receives a larger proportion of the consideration when a power reduction request is not transmitted, and in such a manner that a customer determined as a higher rank by the determination unit and achieving a larger estimated reduction amount calculated by the estimated reduction amount calculation unit receives a larger proportion of the consideration when the power reduction request is transmitted. a first acquisition unit configured to acquire a predicted power demand amount and a power reducible amount for a predetermined period in the future for each customer; a reserve margin trading unit configured to trade the power reducible amount of the customer acquired by the first acquisition unit as a reserve margin for demand adjustment and thereby to acquire a consideration; a second acquisition unit configured to acquire a power consumption amount for each customer; a determination unit configured to calculate, for each customer, a difference between the predicted power demand amount acquired by the first acquisition unit and the power consumption amount for the predetermined period acquired by the second acquisition unit, and to determine a rank of each customer by giving a higher rank to a customer having a smaller value of the calculated difference; a notification unit configured to determine a reduction request amount for each customer based on the power reducible amount acquired by the first acquisition unit and to transmit the reduction request amount to the customer as notification when a power reduction request is sent; an estimated reduction amount calculation unit configured to calculate, for each customer, an estimated reduction amount being an estimated reduction amount of power consumption by use of the predicted power demand amount acquired by the first acquisition unit and a power consumption amount after the reduction request amount transmission calculated by using the power consumption amount acquired by the second acquisition unit; and a trading consideration distribution unit configured to distribute a consideration acquired by the reserve margin trading unit into customers in such a manner that a customer determined as a higher rank by the determination unit receives a larger proportion of the consideration when a power reduction request is not transmitted, and in such a manner that a customer determined as a higher rank by the determination unit and achieving a larger estimated reduction amount calculated by the estimated reduction amount calculation unit receives a larger proportion of the consideration when the power reduction request is transmitted.