Abstract: A disclosed home appliance system comprises: a washer for washing clothes; a dryer for drying the clothes; an external server for communicating with the washer and the dryer; and a mobile device for controlling the washer and the dryer through the external server, wherein the mobile device can: acquire energy peak time information including time-specific energy billing information from the external server; display a first user interface for receiving the selection of a first interworking course of sequentially operating the washer and the dryer; determine a first cycle time of the first interworking course including a first washing time of the washer and a first drying time of the dryer, the first cycle time being required in order to perform the first interworking course; display a second user interface for receiving the selection of whether to perform the first interworking course on the basis of the energy peak time information and the first operation time; and transmit first interworking course informatio