When selecting an air conditioner, tonnage is the most important factor. A "ton" refers to the heat capacity of a ton of melting ice over one day. This means that a 1.5 ton air conditioner can remove enough heat which can melt 1.5 tons of ice in a day. So the bigger the room, the more cooling capacity your air conditioner needs to have; hence, more tonnage. To find out which tonnage will suit your room the best, please share details about your room such as dimensions, facing direction, floor, number of windows, etc.