1. A method of interfacing with an energy management apparatus controlling an energy level of an electric device, the method comprising: displaying, on a screen, a graphical user interface (GUI) element for a user to input a weighted index, which represents a relative increase or decrease between power rates and inconvenience that the user experiences when using the electric device; receiving the weighted index that is input by the user through the displayed GUI element; determining an inconvenience index based on the weighted index that is input by the user through the GUI element on the screen; and displaying the determined inconvenience index that represents a degree of inconvenience, which the user experiences, as a number or a color when the electric device operates at the energy level, wherein the determined inconvenience index has a value proportional to a difference between the inputted weighted index and a preset reference weighted index.