Because of the exhaust hose, it's easy to install a portable AC unit in a room with a window. The hose can simply go right out the window, dropping its exhaust and hot air into the great outdoors. \
Many portable air conditioner units come with window kits to make it easier to stick the exhaust hose out of the window and still have a nice, tight seal around it, and the window so cold air isn't leaking out of your home. \
However, the exhaust hose can go straight through the wall if there is no window present. This should only be done as a last resort, as it will create a hole in your wall that goes through the exterior all the way to the outside. \
Should you ever move your portable AC unit or upgrade to a new HVAC system, this hole in the wall will need to be repaired both inside the room and on the exterior of the wall. \