A method for controlling an inverter in a system including a load, a motor for driving the load, and an inverter for operating the motor comprises when a load amount of the load is reduced to below a sleep level, checking whether a time corresponding to a sleep delay has lapsed; when the load amount of the load is still below the sleep level even after the sleep delay, varying an operating frequency of the motor, and if there is no change in a feedback from the load in response to the variation in the operating frequency, controlling the inverter to enter a sleep mode.