An information processing method by an information processing device, comprising: receiving from a user terminal a reservation request for reserving that a power feeding source vehicle moves to a power feeding destination vehicle to supply power; determining the characteristic information and estimating the upper limit and the lower limit of the charging rate from the characteristic information, the smaller the difference between the clock time when the power is supplied and the clock time when the reservation request is received, the smaller the difference between the upper limit and the lower limit; and transmitting information indicating the upper limit and the lower limit of the charging fee to the user terminal.