A method for operating an electric power source unit for an inhaler is provided. The method includes making a sensor detect a puff action performed by a user; measuring detected-time that is a puff action period during that the detected puff action is continued; correcting the measured detected-time, by using a time correction model that is based on a characteristic parameter associated with the puff action; calculating accumulated detected-time by accumulating the corrected detected-time; and estimating a remaining quantity level of an inhaled component source, based on the accumulated detected-time.