How To Install a Window AC Unit

Installing a new window air conditioning unit can offer much-needed relief during hotter months, especially in homes without a central air system. While it may seem daunting, you can successfully install a window AC unit in your home with the right tools and guidance. We’ll walk you through the step-by-step installation process so you can enjoy cool temperatures in no time.

Tools and Materials Needed for AC Installation

Before beginning installation, gather all the necessary tools and materials. Having everything on hand will make the process easier.

Essential Tools

To install a window AC unit, you’ll need the following tools:

• Power drill
• Screwdriver
• Tape measure
• Torpedo level
• Utility knife

Required Materials

In addition to tools, you’ll need these materials:

• Foam insulation strips
• Mounting brackets (usually included with the unit)
• Screws (if not provided with the unit)
• Weatherstripping
• Window AC unit

Choosing the Right Window AC Unit

Selecting the appropriate window AC unit is crucial for effective cooling and energy efficiency. When choosing, consider both the size of your space and the unit’s energy rating.

Determining the Correct BTU Rating

BTU (British Thermal Unit) ratings indicate the cooling capacity of an AC unit. Here’s a quick guide:

• 5,000–7,000 BTUs for rooms 100–250 square feet
• 7,000–11,000 BTUs for rooms 250–500 square feet
• 11,500–18,000 BTUs for rooms 500–900 square feet

Measure your room’s square footage and choose a unit with the appropriate BTU rating to ensure efficient cooling. There’s also a specific BTU calculator online, but most AC units include the room measurements within the product specifications.

Considering Energy Efficiency

Look for units with high Energy Efficiency Ratio (EER) ratings. EER of an HVAC cooling device is the ratio of output cooling energy (in BTU) per hour to the power input (in watts). A higher EER indicates better energy efficiency, which can lower electricity bills and reduce environmental impact.

Preparing Your Window for AC Installation

Proper preparation of your window is essential for a secure and efficient installation. This involves accurate measurements and removing obstacles that may affect a safe installation.

Measuring the Window Opening

Before buying, you’ll want to check that the window AC unit is the right size. Use a tape measure to determine the width and height of your window opening. Confirm the AC unit you’ve chosen will fit comfortably within these dimensions, allowing for proper sealing and support.

Removing the Window Screen

Before installation, remove the window screen to provide clear access to the window frame. Note that you won’t be able to use a window screen with a window AC unit. Store the screen safely, as you’ll likely want to reinstall it once the cooling season ends.

Step-by-Step Window AC Installation Process

With your window prepared and your AC unit selected, you’re ready to begin the installation process. Follow these three quick steps to set up your AC unit easily.

Step 1: Unboxing and Assembling the AC Unit

Carefully unbox your AC unit, being mindful of the sharp aluminum fins on the back. Assemble any included components, such as side panels or mounting brackets, according to the manufacturer’s instructions.

Step 2: Placing the AC Unit in the Window

To install the AC unit safely, it may be helpful to have a stool, bench, or ladder to support it. Lifting the unit carefully, you should place the bottom bracket outside the window’s bottom lip and the top bracket inside the window. You’ll then want to lower the window sash to hold the unit in place.

Step 3: Securing the Side Panels

Extend the side panels to secure your AC unit in place to fill any gaps between it and the window frame. Your AC unit will include manufacturer instructions for securing the panels to your frame. Typically, you’ll want to use screws or brackets provided with the unit.

Ensuring Proper Tilt and Drainage for Your AC Unit

Keeping your window AC unit in the correct position is crucial for proper operation and drainage. Your unit should have a slightly backward tilt so condensation flows away from your home.

Using a torpedo level, check that your window AC unit is tilted slightly backward. This tilt should be about 1/4-inch from front to back to allow for proper condensation drainage while preventing any leaking into your home.

Most window AC units come with support brackets designed to provide additional stability and maintain the correct degree of tilt. You should install the brackets according to the manufacturer’s instructions, usually by attaching them to the window sill or frame.

If your window sill is uneven, use shims (thin, tapered, or wedged pieces of material) to level the AC unit. This guarantees proper drainage and prevents the unit from rocking or vibrating during operation.

Sealing and Powering Up the AC Unit

Correct sealing and insulation are essential for maximizing your window unit’s efficiency while, most importantly, preventing air leaks. This final part of the installation process helps to maintain cool temperatures inside while simultaneously keeping hot air out.

Applying Weatherstripping

By applying weatherstripping around the edges of an AC unit, you create an airtight seal to prevent drafts, which is essential to the functionality of your window unit. Weatherstripping is applied everywhere the unit meets the window frame.

Using Foam Insulation Strips

Any remaining gaps between your window and the AC unit can be filled with foam insulation strips. These strips can be cut to size and pressed into place to provide additional insulation and prevent air leaks.

Proper Outlet Requirements

The majority of AC window units require a 115-volt, 15-amp circuit. To prevent overloading, avoid plugging your unit into an outlet shared with other high-power appliances.

Using Extension Cords Safely

If the location of your window unit is not close enough to an outlet, you’ll need to use an extension cord specifically designed for air conditioners, such as a heavy-duty 14-gauge cable. You should not use a standard household extension cord because it may not handle an AC unit’s power requirements.

Maintenance Tips for Window AC Units

Regular maintenance is key to keeping your window AC unit running efficiently and extending its lifespan. We suggest cleaning your filter monthly during the cooling season when your unit runs more frequently. You should also wipe down the exterior and interior of the unit with a damp cloth to remove dust and debris. 

For thorough maintenance, you should consider a professional cleaning annually if you plan to use your window unit for years to come. At the very least, you must replace the filter every 3–6 months or more frequently if you live in a dusty area or have pets. A clean filter offers better air quality and functionality.

Alternative Cooling Options

While window AC units are popular, they’re not the only option for cooling your home. If you’re unsure about investing in a new AC window unit, here are a few alternatives.

Portable AC Units

Portable air conditioners do not require a permanent installation and provide flexibility. Portable air conditioners work and are ideal for renters or homeowners who want to move cooling from room to room. Learn how to select a portable air conditioner in this guide.

Through-the-Wall Air Conditioners

Through-the-wall air conditioners are permanently installed on an exterior wall. They offer a more secure and energy-efficient option but require professional installation.

Central Air Conditioning

If you’re looking for a whole-house cooling solution, central air conditioning might be the right choice. This option requires ductwork and professional installation, but it provides even cooling throughout your home. You should think about factors like home size and climate when considering central AC.

Evaporative Coolers

For homeowners living in dry climates, evaporative coolers, also called swamp coolers, can be an effective and energy-efficient cooling option. These units cool the air by evaporating water, adding moisture while lowering temperatures.

Ductless Mini-Split Systems

Ductless mini-split systems are a flexible solution for cooling individual rooms without requiring ductwork. These systems consist of an outdoor unit and one or more indoor units, providing targeted cooling and a less invasive cooling option.

Our Conclusion

Installing a window AC unit is a manageable DIY project that can dramatically improve your home’s comfort during hotter seasons. Choose the right size for your space, prepare your window properly, and follow safety precautions during installation and setup. Regular maintenance will ensure your AC unit will continue running smoothly for years.