摘要： In this paper, we investigate a problem of optimal capacities of energy storage system for the residential users and an optimal unit price energy storage system for an aggregator. We suppose that the residential users have own photovoltaic generation system and a smart meter which can schedule activation of home appliances and controls. The aggregator participates in energy market to maximize his pro?t by selling the storage to the residential users. Each user determines his energy consumption schedule and a required amount of storage to minimize his energy cost depending on the unit price of energy storage, price pro?le of electricity from the main grid and his renewable power generation capacity. We consider electricity bill from main grid and storage bill from the aggregator as users’ energy cost. We formulate a problem for the aggregator to decide an optimal unit price of energy storage and a problem for each user to decide energy consumption schedule and a required amount of storage capacity. With numerical investigation, it is shown that the energy storage can reduce the energy load to main grid and shave peak power. As a result, by purchasing energy storage, users can save their energy cost by 43% in average compared to the case without energy storage.