A package air conditioner is a larger model of a window air conditioner. However, unlike window air conditioners or PTAC units, it has a greater cooling or heating capacity and can typically cool an entire house or commercial building. Nominal capacities range from 3 to 15 tonnes. In this Packaged air conditioner, the conditioned air is transferred to the space to be conditioned via ducting that is typically hidden in the ceiling and walls of the building. The unit is installed outside the home, in a special room within a building, or even on top of a roof. This air conditioner is factory assembled, and skilled technicians are required to install it.