How to Install a Window Air Conditioner

Window air conditioners are simple to install and save big money when compared to construction of a central air system. They can be installed in just a few easy steps and easily removed for storage when the unit is not needed. Below is a basic walk-through of a window air conditioner installation, but users should always consult their owner’s manual for manufacturer specific instructions.

Choosing the Location of the Unit

The perfect location for a window air conditioner is closest to the center of the room and on the shady side of the house. If you need to choose one or the other, pick the shade side. Units located in the hot afternoon sun will be required to work harder to cool the room. You’ll also want to position the unit close to an outlet to avoid using an extension cord. If an extension cord must be used only use one rated for window air conditioner use. (Also, see our Learning Center for more information on the proper power supply rating for your unit)

Prepare and Inspect the Window and Surrounding Area

Inspect the window sill and sashes for any damage or rot and repair if necessary. A rotting sill could become worse with an air conditioning unit mounted on top and it also presents a safety hazard should the unit fall due to disrepair.

It’s also important to remove any obstacles that may interfere with the installation at this stage. Storm window frames and window screens may need to be removed entirely. Also clear the area around the window so it can be accessed easily. Window air conditioning units can often be clumsy to handle so keep the area clear of any tripping hazards. It’s a good idea to recruit a friend to assist with the installation.

Pro Tip: Since this might be the last time the window will be opened for several months clean the inside and outside of the window for clear viewing.

Install Brackets (If Required)

Some units require a bracket to be installed to the outside of the window. These attach to the outside of the house and require some leveling adjustments after installation. When installing these into metal frames, metal screws should be used; wood screws should be used when installing into vinyl or wood. Consult your owner’s manual for specific instructions.

Position and Secure the Unit in the Window Opening

You’re now ready to place the unit into the window opening. Open the window to provide just enough room for placement of the unit and collapse the accordion panels inward to ensure that they do not interfere with initial positioning. Carefully place the unit in the opening and lower the top sash to hold the unit in place. It is important to consult your owner’s manual regarding the angle the unit should be positioned in. Some units require being angled backward to assist with condensation drainage, others do not. Make any adjustments as needed.

Next, expand the accordion panels outward into place to reach the edges of the window and screw them into the bottom sash. If holes are not already present in the bottom sash, pilot holes should be drilled in order prevent the wood from splitting. Use a drill bit slightly smaller than the screw size to make pilot holes.

Next, you must prevent the window sash from moving upward while the air conditioner is installed. Some window air conditioners will come with angle brackets that are used for added security. These L-shaped brackets are installed by fastening them into the front facing of the top window sash and to the top of the bottom window sash. Another alternative is to cut 2 x 2 inch stock to the exact length needed from the top of the bottom window sash to the top frame of the window and wedging the stock between the two.

Weatherproofing and Insulation

Because the window is now open there will be a gap between the two panes of glass . Seal this opening with foam weather stripping that came with the kit, or purchase some from your local hardware store. If the window faces a side of the house that receives a lot of wind or rain it’s a good idea to think about adding caulk to the outside of the window. This added step will improve the air tightness of the installation and keep any water, wind and pests from getting through.

Plug It In

You’re now ready to plug the unit in. Keep in mind to use a properly rated power supply for your unit, and to use a properly rated extension cord, if needed. These cords are rated for heavy current and the packaging will state either “Air Conditioner Cord” or “Major Appliance Cord”.