An evaporator rough-in box includes a flat panel having a first score mark by which the flat panel can be folded between a front wall and a top wall of the rough-in box, and a second score mark by which the flat panel can be folded between the front wall and a bottom wall of the rough-in box. The front wall has an opening through which an interior of the rough-in box can be accessed, the opening being covered by a removable cover plate. Left and right ends of the top and bottom walls include extension pieces bendably attached to central portions of the top and bottom walls to form mounting brackets. The central portions include score marks that delineate knock-out holes by which a lineset and a drain line can be installed to the rough-in box. A drain fitting is attached to the knock-out hole of the drain line.