Disclosed is an air conditioner. The air conditioner includes: an outdoor unit having therein a compressor for compressing refrigerant; at least one indoor unit; a storage configured to store a database on a power quantity used by the air conditioner; and a controller. The controller is configured to: based on the database, calculate an estimated power quantity expected to be used by the air conditioner for at least a part of an entire period, based on a preset maximum power quantity for the entire period and the calculated estimated power quantity, determine a target power quantity for a specific unit time, which is expected to be used by the air conditioner for the specific unit time of the entire period; control the compressor for the specific unit time based on the target power quantity; and in response to arrival of a point in time to update the target power quantity, add, to the database, the power quantity used by the air conditioner for the specific unit time.