Abstract: A group generation apparatus coupled via a communication network to a plurality of consumers coupled to a power system. The group generation apparatus includes: a group size determination unit that determines a number of consumers per group that makes a difference minimum or equal to or smaller than a threshold, between a total sum of demand power of the consumers included in a same group and a forecasted value of the total sum, and a grouping unit that divides the plurality of consumers into a plurality of consumer groups in accordance with the number of consumers determined.