A recognition interface recognizes a reverse flow state in which power flows from a customer's site to a power system or a forward flow state in which power flows from the power system to the customer's site. When the recognition interface recognizes a reverse flow state, a controller causes at least one of a first power storage system through a third power storage system to be charged, based on a priority level related to charge defined for the first power storage system through the third power storage system. When the recognition interface recognizes a forward flow state, the controller causes at least one of the first power storage system through the third power storage system 40c to be discharged, based on a priority level related to discharge defined for the first power storage system 40a through the third power storage system.