A window air conditioner insulation kit to be used with a window air conditioner mounted in a window including a left side panel to be pressed in a first opening between a side of the air conditioner and a left side jamb of the window. A right side panel to be pressed in a second opening between a right side of the air conditioner and a right side jamb of the window. A top panel to extend and be pressed in a third opening between the left side jamb and the right side jamb. The top panel having an upper flap, a first side flap, a second side flap and a central flap which extend down and over an upper section of the first side flap, an upper section of the second side flap and onto the top of the AC.