A network system capable of effectively managing an energy source has a first component and a second component. A first communicator is connected to the first component, and a second communicator is connected to the second component. The first communicator allows communication between the first component and the second component. Communication information between the first component and the second component has information related to energy. The first communicator has a memory that stores information received from the first component and information received from the second component. The first communicator transmits the information stored in the memory to the second communicator when the first communicator receives a message for requesting the information from the second communicator.