How To Install A Window AC Unit – Complete Guide

As temperatures start soaring, we're all looking for ways to escape from the heat.

One of the easiest ways to do this is to install a Window air conditioner (AC) unit in your home.

Even if you're new to DIY, if you're well-prepared, the installation is a breeze.

Project Metrics

Here's what to expect when installing a window AC. 

Working Time

25 minutes

Prep Time

15 minutes

Skill Level

Beginner

Material Cost

This depends on the unit's size, but you can expect to spend between $140 to $200.

Supplies Needed to Install a Window Air Conditioner

Apart from the supplies provided by the manufacturer, you’ll also need the following tools:

How to Install a Window AC Unit

1. Check Your Tools

One of the tricks to being good at DIY is having the right tools. Before you get started, make sure that you have all the tools and materials that you'll need.

Remove the unit and all its parts from the packaging. Make sure all the pieces you need are there.

4. Install the Top Rail

Most units come with a top rail that must be attached to them. The top rail is a safety feature. To prevent the screws from getting stripped, you can screw them in manually. Be sure to tighten them all.

5. Attach the Side Panels

The two accordion-style panels will be marked “left” and "right.”' Slot each one into the correct side of the AC and secure with screws. Push the panels flat against the AC.

6. Insert the AC

Two people need to complete this step.

Together, lift the AC and place it on the bottom window sill. The center of the AC must be where you made your pencil mark at step three.

While one person holds the AC in place, the other should check that the back of the unit is at a slight tilt. The tilt ensures that any water that’s collected can be drained. Close the window now.

Plug in your unit, and don't forget to make sure that the power is on! Enjoy the cool air.

How to Install a Window AC Unit in a Casement/Horizontal Sliding Window

With some basic DIY, you can fit your standard AC into a horizontal sliding window. To secure the AC, you’ll need to build a frame for it. You can do this as follows:

1. Build your bottom frame before inserting the unit into the window. Use a 2x2 cross piece that is the same length as the window to act as the window frame bottom. You’ll screw the bottom of the air conditioner into this instead of the window frame.

2. Use another 2x2 cross piece and attach it to a 1x4 crosspiece (with screws) to create a window ledge. You can use adhesive velcro to attach your new ledge to the existing ledge. It must line up with your new window frame bottom.

3. When you've completed the bottom frame, you can insert the window AC.

4. Add the top of the frame. The top fills the gap above the AC. For this, you can cut a piece of plexiglass to size.

5. To make sure that the space around the plexiglass is airtight, you can seal it with duct tape.

6. If there’s still a gap where the windows connect, you can use a piece of foam core board (cut to size) to fill it.

7. Check the space around the side of the unit. If there are gaps once you extend the panels, you’ll need to seal them. You can use pieces of foam to do this.

How to Install a Window Air Conditioner in a Travel Trailer

AC units can't fit into the regular windows of a travel trailer, so you’ll need to modify them. You can make two adapters out of plywood to slide into the top and bottom of the window. These adaptors will secure the unit and fill up the space between the window and the AC.

How to Install a Window Air Conditioner Without Screws

An easy way to install an AC without screws is to use dowels. You would need two dowels.  The first one fits between the outer window and the inner window, while the second dowel goes between the top of the window frame and the double-hung window. The dowels keep the top window open and the inside window closed. Using dowels is a quick, inexpensive way to secure your AC.

How to Install a Window AC Unit on a Second Floor

When installing an AC unit on the second floor, you may want to further secure it with a brace or bracket. The brace/bracket would fit at the back of the unit and help keep it steady. You can purchase one at a hardware store or online, but be sure to keep your AC measurements on hand.

Conclusion

There's a lot to consider when you're thinking of installing an AC, but it's simple to do with the right tools and preparation. Remember to have someone help you because AC units are heavy, and you need to work with precision.