Ultimate guide to window AC units: Costs, efficiency, and alternatives

Considering buying a window AC unit? Read this guide. You should know about all your options.

Considering buying a window AC unit? Read this guide. You should know about all your options.

We’ve all been there at some point in our lives:

Sleepless in a stuffy, humid, too-hot bedroom, or sweating through a summer movie night in a stale family room… both in need of some fresh, cool air circulation.

Desperately, you open up your phone or laptop searching for a fix: Window AC. 

Do they work? Are they worth it? Are they even energy efficient? Is there something else going on in your house to make it feel so… yucky in the summer?

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Lucky you: You’ve found the right corner of the internet. Before you buy a window AC unit on Amazon and go through all the tricky trouble of installing it (and blocking your natural light while you’re at it), scan through this guide.

At Sealed, we want the best for you, your home, and the planet. If your house qualifies, you could get custom home upgrades—including a super-efficient HVAC system or insulation to fix uneven temperatures—for $0 upfront cost. Find out how.

Table of contents:

Key points:

  • Figuring out if a window AC unit will work well for your house depends on what problem you’re trying to solve. (We’ll give you some key questions to think through below!)
  • Window AC units offer an affordable short-term fix if you’re a renter or a homeowner who isn’t quite ready to solve their house’s underlying temperature problems.
  • If you’re considering a window unit to save on energy costs, think again. They’re not the most energy-efficient solution to uneven temperatures or a too-hot upstairs bedroom, especially if you run them at the same time as central AC.
  • Yes, AC heat window units exist. But there’s a better solution than ruining your view or blasting heat out a window. Read on to find out what it is—or skip ahead to see if you qualify for $0 upfront cost heat pump upgrades with Sealed.

Do window AC units work well?

Okay, so if you’re trying to decide if a window AC unit is the right solution for you, the first thing you might be asking is if it’ll work well to keep you cooler during the summer.

Overall, energy-efficient window AC units work well as a short-term solution for an uncomfortable room that’s on the small side—especially for renters. 

Although window units are far from ideal from a noise or decor perspective, they can get the job done.

But ultimately, whether or not window AC units “work well” really depends on what problem you’re trying to fix. 

Whether or not window AC units ‘work well’ really depends on what problem you’re trying to fix. 

Here are a few questions to think through before you click “add to cart” on a window AC unit from a big-box home improvement website:

  • Do you have one room that’s really uncomfortable (or several rooms)?
  • Is the comfort issue you’re trying to fix located upstairs or downstairs?
  • Is this a smaller room that needs supplemental cooling or a larger living space?
  • Do you have central air conditioning already? If so, when was the last time you replaced your air filter? (Most require a fresh replacement every 90 days!)
  • Are you a renter or a homeowner?

If you’re a homeowner, we’ve got a few more questions for you:

  • How old is your current HVAC system? Is it time for a central AC update? Tap here to learn when to replace AC.
  • Do you have existing ductwork? If so, is it in good condition or does it need duct sealing?
  • When did you last upgrade your insulation and air seal your house?
  • Is your house simply too stuffy and hot in summer? Or is it too cold and drafty in winter, too?
  • When was the last time your house had a professional energy audit completed?

If you’ve realized that you have uneven temperatures throughout your house (and throughout the year)—or an older HVAC system in its final years—a window AC unit isn’t going to work well for solving your underlying problem.

And here’s why.

(Friendly note here: You’re welcome to skip this next section if your house has been recently insulated and air sealed. Tap here to jump ahead.)

a GIF of a window AC photo illustrating open gaps and seams around the unit that create air leaks and allow outside air indoors
Open gaps and seams around window units (called air leaks) cause outside air to get inside, making your window unit AC work harder and your house feel more uncomfortable. Even a well-installed unit can allow unwanted airflow into your home.

The real fix for uneven temperatures and too-hot rooms

We’ve worked with hundreds and hundreds of homes, and we can tell you this confidently: 90% of US homes are under-insulated (1). And about 85% of single-family homes were built before energy efficiency was top of mind.* 

That means most American households are dealing with some sort of unnecessary energy waste or too stuffy, drafty, or uncomfortably hot rooms

But why does insulation and overall energy efficiency matter if you’re looking to get a window AC unit? 

Well, under-insulated homes have big problems with uneven temperatures, energy waste, uncomfortable rooms, and too much humidity. This can also make your existing HVAC system work too hard (and too much!). 

It can be tempting to grab a window AC unit at your nearest store to bandage up the problem.

But if you’re adding window AC units to solve the issue of uneven, uncomfortable temperatures, you’re just burning through more energy—and in one of the noisiest ways possible.

Adding a window AC unit means you’re just burning through more energy—and in one of the noisiest ways possible.

These uncomfortable, uneven temperatures happen in your home because of a couple building science principles: 

  1. One principle is called the stack effect 
  2. And the other principle at play is a combination of your house’s thermal boundary and building envelope.

Here’s a quick overview of how this combo makes your home feel uncomfortable and waste energy:

  • When your house has air leaks, that means your home has holes in its building envelope—or that it’s leaky.

    The stack effect causes your house to take in outside air through those open gaps and seams, and this makes your HVAC work harder and the temperatures throughout your home uneven. Professional air sealing is the right way to fix this.

  • If you have an under-insulated attic, an attached garage that isn’t insulated—or even uninsulated hidden attics—these can radiate heat straight into your home, creating hot spots in the summer.

    Insulation is what puts a boundary between your indoor temperature and outside temperatures—it’s your home’s thermal boundary. Getting the right insulation upgrades solves the issue.

  • Even if you have a central HVAC system, a leaky, under-insulated house causes your AC unit to be inefficient and have a shorter lifespan.

    Once you address those underlying issues, a super-efficient heat pump can dramatically improve your comfort, reduce your energy waste, and offer flexible installation that doesn’t require ductwork. Heat pumps are excellent AC choices on their own, but fixing uneven temperatures is also part of the long-term solution. 

For a deeper dive, read all about the ins-and-outs of the stack effect in Why is my upstairs so hot? or Why is my house so drafty? 

Or watch this short video below to learn how outside air gets inside your house…

Before we move on, know this: 

Even if you install a new energy-efficient window AC unit in every room—or even if you install a super-efficient heat pump HVAC system—you’re still going to have the same problem if you don’t solve your insulation issue. 

But what if you have an older, worn-out HVAC system—one that’s no longer up to snuff? 

Well, a window AC unit isn’t the right long-term fix for that, either. 

51% of your home’s energy consumption is for heating and cooling alone.

U.S. Energy Information Administration

That’s why we created a plan to solve these issues for good: Heat pump HVAC systems are the most efficient way on the planet to cool and heat your home. Pair that with up-to-date insulation and air sealing, and you’ve got yourself an amazing-feeling, healthier, less-wasteful house—year round and long-term. 

See if you qualify for custom home energy upgrades at $0 upfront cost with Sealed.

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What good insulation and window AC units can accomplish together—a real-life example

We’ll stand by the fact that a heat pump is the best heating and cooling system for any home—and if you don’t have central ductwork, skip the window AC units because ductless mini-split heat pumps are the way to go.

But here’s an interesting story:

In May 2022, this writer and her family stayed in a cozy, tiny Nashville bungalow that had been thoughtfully redone with comfort (and the planet!) in mind. 

I had lived in Nashville for 12 years and was back in town for a quick visit, and one of the places I rented in Nashville when I was just out of college (an older, tiny home built in the 1920s) had one window air conditioning unit. It was terrible—and noisy, windy, and uncomfortable. 

If you’ve ever been in the South on a hot, humid May day, you know things can quickly get sticky, sweaty, and desperately uncomfortable. So when I realized we scheduled a vacation rental with—gasp!—window AC units, I was nervous.

But the owner had upgraded the older tiny home with sheep’s wool insulation in the walls (one of the most planet-friendly ways to insulate a home), and I could instantly feel how comfortable the house was when I stepped in it. It didn’t feel like an older house with rickety window AC… at all. 

And much to my surprise—and although they were noisy compared to mini-split AC—the window units did a decent job and the house was cool and fresh… despite the sticky summer air outside. 

Behold the power of a well-insulated home: No matter what type of heating or cooling unit you have, proper insulation and air sealing is definitely going to make the most of it. 

That’s why incentives like insulation tax credits and rebates and income-based weatherization programs can help you get these crucial home improvements.

Pros and cons of window AC units

Okay, so now that you have a better understanding of how insulation works to keep your home more comfortable—no matter how you cool your indoor air—let’s look at the pros and cons of window units.

Pros of window unit AC

  1. They’re affordable.
    Window AC units can be a lower-cost short-term solution for your cooling needs, especially for small spaces or single rooms. They are generally less expensive to purchase and install than central air systems.
  2. They can be installed without ductwork.
    Window AC units have a fairly straightforward installation process and don’t necessarily require professional installation. However, they do take some determination to install, so call an electrician or HVAC professional if needed. Safety first!
  3. They’re portable.
    Window AC units can be moved and re-installed in different rooms, making them fairly versatile. But they’re a hassle to move from room to room. So if you want AC that follows you around, it’s better to go with ductless mini splits or a portable air conditioner.
  4. You can have different temperatures in different rooms.
    Window AC units give you individual control in each room, allowing for greater customization. But you can get this same benefit with mini-split AC—and without blocking all your windows!

Cons of window unit AC

  1. They’re inefficient.

    Window AC units can be much less energy efficient than other types of cooling systems, especially if they’re too large for the room they’re cooling. And guess what? This inefficiency can lead to higher energy bills and unnecessary energy waste.
    The most energy-efficient way to heat and cool your home is with a heat pump—hands down.
  2. Their cooling range is limited.

    These AC units are designed to be placed within a window to cool a single room or small area, so they’re not the best choice for larger homes, rooms with vaulted ceilings, or open-concept living spaces.
  3. They’re unsightly.

    Okay, so we can all acknowledge that window AC units don’t look the best. In fact, they’re… downright ugly. Although newer, sleeker designs are out there, even if you’re not into interior design, they can be an eyesore and block your view.
  4. They’re loud.

    Window AC units can be noisy, especially if they’re not maintained properly. When they cycle on and off during the night, they can interfere with your sleep.
  5. They can cause security concerns.

    It’s true: Using a window AC can create a security risk. Installing them incorrectly in the window creates an easy entry point for intruders.
  6. They’ve got problems—lots.

    They leak water, and if the drain line isn’t clear, it can leak out the front and inside your house. Even when they’re draining properly, they can stain your house’s siding. Window AC units are also prone to creating air leaks—even if they’re installed well—which allows outside airflow into your home.

Are window AC units safe?

Window units can make it easier for burglars to break in your home if proper measures aren’t taken. So support brackets, sliding window locks on your window frame, and correct installation is key.

Check out this video below for tips on how to secure a unit safely.

Even though they can cause security risks, window AC units are generally safe to use with proper installation and maintenance. 

And keep in mind: Without regular maintenance, window AC units are more prone to mold and mildew than central AC. Make sure to follow the manufacturer’s recommendations for regular cleaning.

Do window AC units use a lot of electricity?

Window AC units can use a surprising amount of electricity, especially if they are not properly maintained or if they are used for an extended time. Generally, the larger the unit and the lower the temp setting, the more electricity you’re going to use.

However, the amount of energy your window AC unit ends up using will depend on a few things, including the:

  • Size of your unit 
  • Efficiency rating 
  • Size of the room you’re trying to cool (including how high the ceilings are!)
  • Temperature settings

Curiously, even though window AC units are smaller, central air-source heat pumps and ductless mini-split heat pump systems make much better use of electricity when you’re trying to cool a whole home. 

An added bonus? Heat pumps are whisper-quiet, unlike window AC units.

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Cost vs. benefit analysis: Window AC vs. central HVAC systems

While window AC units are generally less expensive to purchase and install than central HVAC systems (they can cost anywhere from $150 to $500 for one window unit alone), they can’t provide the same level of comfort—or energy efficiency. 

Central HVAC systems—especially super-impressive heat pump HVAC systems—cost more upfront to install, but use less energy to cool an entire home. They are also more reliable, easier to maintain, and less noisy than window AC. 

While the upfront cost of installing central HVAC can be higher, it can save energy in the long run. Not to mention, it’s an energy-efficiency upgrade that can increase your home’s value.

If you’re having trouble deciding, you can do a basic cost vs. benefit analysis:

  • Calculate how many window units you’ll need to make your space feel better
  • Research which size units you’ll need and note the pricing and efficiency of each unit
  • Calculate the cost of how many units you’ll need total and price to install (if you’re skipping the DIY route)
  • Calculate the total cost per day to run each unit and multiply that by 30 to get an estimated monthly cost
  • Add up the estimated monthly cost to run the window units plus the initial costs to purchase and install them
  • Add up all of those appliance, installation, maintenance, and use costs and estimate overall costs per year based on how long the window unit will last. (Heat pumps and central AC tend to last significantly longer.)
  • Research any rebates or financial incentives that might be available to offset the total cost
  • Compare that to quotes for installing home energy upgrades that will fix your house’s underlying comfort problems. 

If your house qualifies for Sealed, our experts will design a customized home comfort makeover for you—including heat pump HVAC if you need it—and help you understand any federal or local rebates you could qualify for. 

Sealed experts can design a customized home comfort makeover for you that includes any federal or local rebates you qualify for. 

Get home upgrades at $0 upfront cost with Sealed, and pay for the work done with a flexible payment option that’s best for you. See if your house qualifies.

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Are window AC units worth it?

Window AC units can keep your home cooler during the warmer months and have a lower installation cost than long-term fixes. However, as we mentioned above, they’re usually a short-term solution to a larger underlying problem: an issue with your home’s building envelope and thermal boundary that causes you to lose comfortable, conditioned air you’ve paid for. 

If you’re a renter, window AC units can be a low-effort fix and help you feel more comfortable in a house where you’re unable to make permanent changes. 

But be forewarned: They’ll increase your utility bills.  

Overall, their energy efficiency varies depending on the size and age of the unit and the amount of square footage you’re trying to cool. And if you have an older unit or one that’s too large for the space you’re cooling, you could be wasting energy (and money!). 

If you choose to go the window AC route, make sure to look for the ENERGY STAR label.

And if DIY isn’t for you, call a professional to help with getting the right unit for your room size and the installation process—that way, you make sure you’re getting the best efficiency.

Skip the view-blocking window units. Get comfortable at home—once and for all—with Sealed

You could get a whole-home comfort makeover—with a money-back guarantee.

Keep your view and natural light and sleep more peacefully all summer long with cooler temperatures and whisper-quiet HVAC. 

If you qualify for Sealed, get $0 upfront home energy upgrades without the hassle. 

Keep your view and natural light and sleep more peacefully all summer long with even temperatures and whisper-quiet HVAC. 

See if you qualify today.

FAQs about window AC units: 

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How can I save electricity with my window air conditioner?

A correctly insulated and air sealed house can help you reduce your energy use when you’re using your window unit. You can also plug your window unit into a smart plug, or plug with a timer, to have more control of when it runs. 

And don’t forget: Proper installation of your unit and regular maintenance (make sure to clean that air filter!) will also help make sure it’s running efficiently and using electricity wisely.

Do window AC units need to be recharged?

Not necessarily. Air conditioning units are designed to have the refrigerant needed for their lifespan. So if your window AC isn’t cooling properly, it may have a refrigerant leak or need to be replaced entirely. Even in the event of a refrigerant leak, it’s often cheaper to replace the whole window unit than to try and diagnose and repair it.

And if your window AC is getting close to eight years old or more, it’s time to go ahead and replace it. You may need an upgrade sooner if it hasn’t been maintained properly over its lifespan. Learn why heat pumps are the better option in our heat pump vs. AC guide.

How much do window AC units cost to run?

A 8,000 BTU window AC unit, which is about the size window unit you’d need for a 200-square-foot room, will cost between $1 to $2.50 a day, depending on electricity prices in your area and how long you run it during the day (2).

Based on that estimated range, you’re looking at anywhere from $30 to $75 a month to run one window unit alone—and possibly even more if you live in an area with higher-than-average electricity costs. 

Keep in mind: Window AC units are designed to cool a small area only. If you need to cool multiple rooms in your home, you’ll need to run more units. For example, if you have two bedrooms and one living space that need window units, you’re looking at running three separate units, costing anywhere from $90 to $225 a month total to run.

Oh, and we don’t want to leave you wondering what a BTU is: It stands for British thermal unit, and it measures how much energy it takes for your HVAC unit to move around heat.

Do window AC units have heat?

Window AC models that contain supplemental heat do exist, but they’re pretty similar to using a space heater… with your window partially open. It’s not the best idea. If you’re looking for ductless heating and cooling options, check out mini splits—they’re the way to go.

And if you’re a renter who needs both temporary cooling and heating that’s portable? Check out Gradient, the window unit heat pump that’s an excellent energy-efficient option for renters and small spaces, like New York apartments.

Does a window AC unit have to be in a window to work?

Yes, definitely. (Although some AC unit models can be installed into your drywall… but you probably want to skip cutting a huge hole in your house.) If you need a portable, moveable AC unit, check out one of these models. Next question!

How much is a window AC unit?

Window AC units cost anywhere from $150 to over $500 per individual unit, depending on the features you’d like to have. If you want an option with heating included—which we don’t recommend—the price per unit increases. If you’re looking for efficient heating and cooling that doesn’t require ductwork, check out ductless mini splits.

You could get super-efficient heat pump HVAC (or ductless mini splits) at no upfront cost. Find out which ones are right for your home:

*85% of American single-family homes were built before 2000, when residential energy-efficiency standards became prevalent in building codes.

May 12, 2023