How to Install a Window Air Conditioner in 7 Steps

window ac unit

We all know how scorching hot Canadian summers can be — and how the heat can make it uncomfortable in our homes. If your living space isn’t set up for central AC, a window air conditioning unit is an effective alternative to stay cool. And while installing a window air conditioner by yourself may seem like a daunting task, it doesn’t have to be. Keep reading to find out how to install a window AC for your home in seven simple steps. 

How to Get Ready to Install Your Window AC

Before you get started, there’s a bit of prep work that has to be done. First, make sure you’re installing the right AC unit for your space. If you’re unsure which air conditioner will best suit your needs, consult our definitive buyer’s guide to air conditioners

Once you’ve decided which window air conditioner you’d like to install, it’s time to choose the window you’ll be installing it in. You’ll want to consider many different factors, including: 

  • Frame: Inspect the window’s size to make sure it is the right fit for the air conditioner you want to install. 
  • Design: Most AC units are designed for double-hung windows. If your window is a sliding window, check whether the air conditioner you’ve chosen is actually suitable for such installation. 
  • Brackets: Not all window air conditioners include support brackets for the outside of your window. (Brackets transfer the AC unit’s weight more evenly so the load isn’t placed entirely on your windowsill and sash.) Know beforehand whether you’ll need to purchase them separately.
  • Power supply: Ideally, a three-pronged outlet will be within reach of the power cable of the air conditioner. Extension cords are an option but do not always provide sufficient power to the unit.
  • Location: Ensure your window is free from obstructions. You may need to remove storm window frames or branches growing too close to the window. If possible, choose a window that is partially shaded and doesn’t receive too much sunlight, which could affect the unit’s performance. You should also make sure the air conditioning unit is not installed in an egress window or fire escape route, as this may violate fire safety codes and put yourself and others at risk.

In addition, the windowsill must be sturdy and without any damage, otherwise it might not be able to support the weight of the air conditioning unit. If you see any damage or rotted wood on your window, address these repairs first before trying to install the AC unit.

On the actual day of the installation, make sure you have everything in place and ready to go to make things as smooth and simple as possible. That includes: 

  • Clear your workspace and keep it organized. Make sure there are no tripping hazards.
  • Keep a measuring tape and a screwdriver at hand. Some units also require that you have a pair of scissors available for installation.
  • Get somebody to assist you with the installation. Air conditioning units are heavy, so having an extra set of hands to lift and handle the unit will help avoid accidental drops and damage.

7 Steps for Installing a Window Air Conditioner

Now it’s time to install your window air conditioner. Carefully remove the unit from the box, then take out the owner’s manual and follow along as you go through the following seven steps.

Step 1: Prepare Your Window

Wash the glass of your window before installing the air conditioning unit. A clean window frame, free of dirt and debris, will protect your unit and make installation easier. Also, once the air conditioner is installed, cleaning the window will be more difficult — so do it now while you still can!

Step 2: Position and Secure Bottom Window Sash

For an easier installation, mark the centre of the windowsill with a pencil. Precise measurements will ensure the unit is positioned properly and the side panels will reach the window frame on both sides. Slide up the bottom window sash (the movable part of the window) and temporarily lock it in place with a screw or piece of wood to prevent it from closing during the installation. 

Step 3: Install Weather Strips (Optional)

Some manufacturers will provide weatherstrips with their air conditioners, but they can be purchased separately as well. Though not required, they effectively seal small gaps and cracks and also protect the window from scratches and warping damage. Install them now to help prevent hot air, moisture, rain, dust, insects and drafts from entering your living space.

Step 4: Attach Side Panels and Brackets

The accordion-style side panels cover and seal the gaps between the AC unit and the window frame. Position the panels properly on the AC unit, then slide them into their appropriate slot and attach them with the screws provided. 

While not mandatory, now is the time to install brackets on the outside of your window if you want to provide additional support for your air conditioner. 

Step 5: Mount and Secure the Air Conditioner

Lift the air conditioner into the window, using the pencil mark you made earlier to centre the AC unit within the window frame. Depending on the model, there may be a flange or mounting rail on the bottom and top of your air conditioner to align and interlock with your window frame. Once the unit is positioned securely, close the sash and lock it in place by attaching L-shaped clips or screws for added stability.

Now that the air conditioner rests securely in the window, fully extend the accordion-style panels to each side of the window. They will help prevent hot air from coming in and cold air from leaking out. Screw or clip them in place. 

Step 6: Fill Gaps with Foam Seals

While the side panels help keep hot air from entering your space, you may still want to add additional insulation, especially if your window receives a lot of sunlight during the day. Extra insulation will help prevent the air conditioner from running unnecessarily, ultimately helping to prolong the unit’s lifespan. 

Cut the foam seals to size and use them to fill the space between the frame of the bottom sash and the window of the upper sash. If you need new or additional foam seals, or if none were provided with your air conditioner, you can buy them separately.

Step 7: Power On the AC Unit

As a last step, plug your window air conditioner into a nearby power outlet. Now all that is left to do is to sit back and enjoy the cool air in your living space!

Window Air Conditioner Installation FAQs

Is there something we missed? Here are some of the most frequently asked questions and their answers. 

How Do You Install a Window Air Conditioner Unit Without Side Panels?

If your unit does not come with side panels or if they don’t fit, you’ll need to find other solutions to stop cold air from getting out and hot air from coming in. You can use plywood, plexiglass, or other material to seal the space. You can also purchase replacement side panels at your local hardware store or online.

Can a Window Air Conditioner Be Installed in a Sliding Window?

Most units are designed for double-hung windows. If your living space has sliding windows only, you can build a wooden frame to support the installation of the unit.

Can You Install a Window AC Unit Sideways?

It is not recommended to install a window unit sideways. Condensation and rainwater will not drain properly, freon may leak and the processor may get damaged, creating a serious fire hazard.

Can You Install a Window Unit Without Drilling or Screwing?

It is possible to install a window unit without drilling or screwing, but always make sure the unit is secured safely. The installation of brackets on the outside may be necessary to prevent serious accidents and potential damage to your house.

Stay Cool with a Ductless AC Unit

If installing a window AC unit isn’t the right fit for your home, consider getting a ductless air conditioner instead.  A ductless AC system can be added to your home without having to open walls and add or modify ductwork; plus, they’re efficient and can target specific rooms in your home. If you’d like to explore purchasing a ductless AC unit, Enercare is ready to help with licensed technicians who can install your AC unit to ensure safe, efficient cooling throughout your home.