An energy management system for managing energy such as power consumed in a building in an optimal state to significantly save energy is provided. A computer control system (200) for controlling the energy management system performs program control as follows. Current date and time are acquired, a control pattern for that time is obtained using a control program, so as to determine whether operation of an air conditioner (186) is to be turned ON or OFF, and then output either an operation instruction or a stop instruction. A control signal is then output from a digital output unit (212) to the air conditioner (186). Thus, the air conditioner (186) temporarily stops operation according to a predetermined pattern for the program control. The current operating state is displayed on a display unit (240) and a remote monitoring unit (270).