How To Install A Window Air Conditioner (10 steps)

Homes and apartments across the country utilize portable air conditioners to keep occupants cool during periods of hot weather. These units are easy to install but need to be installed safely for your protection. It is essential that your portable air conditioning unit be sized properly for the window it will be placed in. Follow these instructions to install a window air conditioner unit properly.

Materials Needed

  • Measuring tape
  • Level
  • Foam strip
  • Mounting brackets
  • Screws (wood or sheet metal screws)
  • Screwdriver
  • Drill
  • Waterproof caulk (or any other weatherproof sealant)
  • Caulking gun


  1. Measure the window where you would like to install the unit to make sure it is large enough to accommodate the unit’s size.
  2. Open the window to install the mounting brackets onto the windowsill. Screw one end into the sill and adjust the center screw on the bracket so the air conditioner will be level.
  3. If your window frame has a lip, set a wood strip on the exterior window sill. The wood strip should be level to the top of the lip of your window sill to provide stability for the portable air conditioner and stabilize the window lip.
  4. Set the air conditioner unit in the window, moving it over the sill and onto the mounting brackets. Continue pushing it back until the top lip of the unit reaches the pane.
  5. Close the window, and check to see that the unit lip and window fit snugly together.
  6. Pull out the extensions on either side of the air conditioner until they reach each side of the window (you may have to reposition the unit to get it centered).
  7. Using the screws that came with your unit, attach the side panes to the window frame.
  8. Look around the unit at the areas where the window and unit touch. If you see areas where light comes through, use foam stripping to create a seal.
  9. Go outside and caulk around the AC unit to prevent any rain, dirt, bugs (etc.) to get inside your home.
  10. Connect the air conditioner to a grounded outlet. You should have a dedicated outlet that is only for your portable air conditioner to prevent the circuit from becoming overloaded and tripping your breakers.