POWER CALCULATION APPARATUS AND POWER CALCULATION METHOD

A power calculation apparatus includes: a power-amount acquisition unit (111) configured to acquire a power amount information regarding amounts of power input to and output from a plurality of vehicles, the amounts of power being detected by a plurality of measuring instruments provided in the plurality of vehicles or interposed between a power grid and the plurality of vehicles; a group setting unit (112) configured to classify the plurality of measuring instruments based on errors possessed by the plurality of measuring instruments to set a plurality of groups; and a power-amount calculation unit (113) configured to calculate a total power input and output in each of the groups, based on the power amount information. The group setting unit (112) sets the plurality of groups such that a mean value of errors of amounts of power in the groups is a predetermined value or less.