A power management system includes a first administrator, a second administrator, a first estimator, a second estimator and a determiner. The first administrator manages a residual capacity of a power storage apparatus. The second administrator manages interruption information regarding a power grid. The first estimator estimates, as first power information, an amount of power that is consumed by an electric load during an interruption period. The second estimator estimates an estimation residual capacity that is the residual capacity at an end point of the interruption period, based on the first power information. The determiner determines that a condition for participating in a power trade market is met, when the estimation residual capacity exceeds a reference value.