The number of air conditioners refers to the cooling capacity of air conditioners. The more air conditioners, the greater the cooling capacity and the better the cooling effect. A 3-horse air conditioner can meet the cooling demand of a 39-square-meter room, while two 1.5-horse air conditioners have a total cooling capacity of 3 horses, but the cooling effect may be inferior. So compared with the two, a 39-square-meter room with three air conditioners will be fine.