Disclosed is an air conditioner. The air conditioner includes an outdoor unit. The air conditioner further includes an indoor unit located in a building and configured to distribute cool air to a space within the building. The air conditioner further includes an antenna unit configured to sense (i) movement of human bodies within the space or (ii) presence of human bodies located in the space and determine a number of human bodies based on the sensed presence, where the antenna unit includes a housing and a plurality of antenna arrays located on an outer surface of the housing.