How to Install a Window Air Conditioner

Are you thinking of installing a small window air conditioner but don't want to hire an HVAC specialist? Well, we have good news: It's easier than you think. With some planning and the right tools, you'll be able to complete this DIY project in no time.

Here are some helpful tips for choosing and installing a window air conditioner.

1. Plan it out. 

Before you purchase and install a window A/C unit, you’re going to have to do some homework on air conditioner maintenance and research for window installation. Unless you want to hire an electrician, make sure you have the electrical requirements for an air conditioner window unit, as well as the right kind of plug. If you don’t have an outlet within easy reach of the window, you’ll need to purchase an extension cord labeled specifically for air conditioners. 

2. Choose the right window. 

Make sure that the air conditioner you select is designed for the type of window that will house it. Do you need a vertical window air conditioner? Is it double-hung or casement, or do you need an air conditioner for a sliding window? Many units require a sash or double-hung window that can be raised and lowered, so if you have another kind of window, you’ll need to shop for a unit that is compatible. 

It’s important to accurately measure the width and height of the inside of the window frame to make sure the window unit will fit properly. Window unit air conditioners won’t cool the air unless properly vented and installed, so it’s important not to guess. 

You’ll also want to assess the condition of the window. It should be sturdy and not show signs of wear and tear. Window air conditioners can be really heavy—make sure your window can handle the weight. You may also want to invest in a support bracket to help distribute the pressure.  

3. Pick the right unit.

Measure your room size to ensure the air conditioner can adequately cool the area. The cooling capacity of air conditioners is rated in British thermal units, or BTUs. Ask your local home store or air conditioner retailer to help you calculate how many BTUs you need for cooling your specific area. If you pick the smallest window air conditioner, it may not be effective if the room has high ceilings or if the window is in a sunny spot. 

It's important to consider the energy efficiency ratio, or EER, of the unit that you purchase. The EER measures how well the air conditioner converts cooling energy; a higher rating means higher energy efficiency. Units with the ENERGY STAR certification use 10 percent less energy and cost less per year to run than those that aren’t ENERGY STAR-certified. 

You’ll also want to look for other cooling features that can help increase energy efficiency and enhance your comfort, such as variable fan speeds, digital temperature control, energy-saving settings, and timers. Once you’ve chosen the best window air conditioner for your room, it's time to get the ball rolling with installation. 

4. Gather your tools. 

Before you get started, gather the following tools:

  • Tape measure 
  • Drill 
  • Screwdriver
  • Safety goggles 
  • Insulating foam panels or strips, or a window air conditioner kit 
  • Torpedo level 
  • Heavy work gloves

It’s also helpful to have an extra person around to assist with lifting and positioning the unit, so ask a friend or family member to be present when it's time to install the window air conditioner.

5. Begin installation. 

Prepare your window. If there’s a storm window, you’ll have to remove it or affix a spacer block to the windowsill to raise the air conditioner away from the storm window frame. After you’ve prepared the window, read the manufacturer’s installation instructions carefully before starting the mounting process. Attach any rails, flanges, brackets, or panels that need to be installed before placing the unit into the window.

Mount the air conditioner on the window. With the window opened wide, position the window unit air conditioner in the center, placing the bottom flange on the window seal. Close the window onto the unit. Before going any further, make sure that the unit will be level so that it will operate properly. Check the air conditioner’s position with a torpedo level and adjust accordingly before anchoring it into place.

Secure it in place. Affix any brackets that came with the assembly kit by drilling pilot holes and tightening the screws with a screwdriver. Open the side panels and insert screws or clips to immobilize them, and add foam strips or panels around all sides, as needed, to seal off the unit as completely as possible. A good air conditioning seal prevents cool air from escaping the room and prevents insects and moisture from entering.

Test your A/C unit. After you’ve made sure that all the air conditioner window unit parts are installed correctly, it’s time to plug it in and turn it on. Avoid placing other electrical appliances, like lamps or televisions, near the air conditioner’s thermostat, as the heat from these appliances can signal the air conditioner to cool longer. For the greatest energy efficiency (and lower utility bills), choose the highest comfortable thermostat setting, and avoid running the unit when you’re not in the room or out of the house. 

If you decide to upgrade to HVAC in the future, keep our home warranty plans in mind. Replacing your air conditioner out of pocket can be pricey, so our coverage includes an air conditioner warranty to protect your budget from breakdowns due to the everyday wear and tear to major components of your unit. Our network of qualified service contractors can help diagnose covered air conditioner problems and determine if a repair or replacement is necessary. The only thing you’ll have to do is keep running your household like a pro. Protect your budget from covered appliance breakdowns with a home warranty from American Home Shield®. Learn more about our pricing and plan information

Now you can beat the heat with your window air conditioner and take pride in another homeowner DIY task checked off your list. 

AHS assumes no responsibility, and specifically disclaims all liability, for your use of any and all information contained herein.

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