Can you install a window air conditioner on its side?

NO, NO, NO ! The compresser is made to have the freon or oil in it at all times. turning it on its side , the oil (freon) runs out . The compresser burns up . Your at the store ,to buy a new AC. The same goes for a refrigerator. IF you lay one down to move it , you should wate 24 Hr before you plug it back in. Assuming that the reason for the question is that you have a narrow window you wish to place the a/c in a little research will help you find an a/c that is made taller than wide just for this purpose. They cost more that a standard demension a/c. There are companies that make roll around a/c units that only require a panel be placed in a window or other exhaust avenue. The panel can be installed either horizontally or vertically. I used one this past a/c season and let me tell you, it sure beats all the hassle of installing and uninstalling the a/c in the window and having to seal it every cooling season.