Skip to main content

How To Install a Window Air Conditioner

Heat wave got you down? Unleash an arctic blast with these steps.


  • Step 1: Use scissors to trim the weather stripping that came with the AC to fit the space between the upper and lower sash. Put the stripping in the gap to insulate the window and keep pests out.
  • TIP: Cover floor intakes or vents with foil or insulation to keep the cool air in the room.
  • Step 2: Plug the AC unit in, turn it on and relish your triumph over the elements.
  • FACT: If every window AC in the U.S. were Energy Star rated, it would prevent more than a billion pounds of greenhouse gas emissions.
  • TIP: You can also cut a board to fit vertically between the top of the lower sash and the head jamb to prevent the window from opening.
  • Step 3: Extend the panels to the sides of the window frame. Drill pilot holes, and use screws to secure the accordion panels to the window. Then, attach L-brackets between the upper and lower sashes to keep the window from sliding open.
  • Step 4: If the AC unit came with a mounting bracket, attach it to the outside of the windowsill. Center it and mark where the screws will go. Drill pilot holes using a bit with a slightly smaller diameter than the screws. Then, screw the brackets into place using wood screws for a wood windowsill and sheet-metal screws for vinyl or metal sills.
  • Step 5: Place a level on the bracket and adjust it with the adjustment screws, or with shims placed between the bracket and sill, until the bracket is level.
  • Step 6: Open the window several inches wider than the height of the AC unit. Lift the unit and place it in the window so it rests on the bracket and the accordion panels fit in the window track. Lower the window so it fits tightly behind lip on top of the accordion panels and the AC unit.
  • Step 7: Measure the innermost width of the window and choose an AC that will fit.

Popular Categories