Suppose a special district (group) that is composed of multiple companies (agents) imposed energy demand. We have proposed a Distributed Energy Management System (DEMS) that optimizes energy consumption of a group through energy trading in the group. In this paper, we propose an efficient operation planning method for DEMS with storage device. At first, we formulate the optimization problem for agents. Secondly, we propose a method to search a unit commitment state that depends on group composition. We confirmed that the proposed method enables efficient use of generators in groups.