How to Buy a Used Air Conditioner

Updated June 2, 2023

Thom Dunn

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There are a lot of mediocre, brand-new air conditioners out there. (Trust us. We’ve tested most of them.) They can be loud, inefficient, unintuitive, and occasionally glitchy—and somehow still cost $300 or more. If you want to save money, we think you’re better off getting a used machine, as long as it's no more than 10 years old.

In fact, in our guide to window air conditioners, we recommend used air conditioners as our budget pick.

There's an environmental case for buying a used AC, too. Americans throw away an estimated 6 million window AC units per year (PDF), according to the Environmental Protection Agency. That's roughly 200,000 tons of metal, plastic, and styrofoam waste piling up year after year. ACs also contain potentially harmful refrigerant chemicals that require proper disposal. By buying a used model, you’re prolonging the life of a big machine and (for a time) keeping harmful materials out of the environment.

But don't settle for just any old air conditioner. Otherwise, even a free AC unit could be more hassle than it's worth. Below, we share how to save yourself an extra trip to the curb or recycling center.

If you’re on the hunt for a used air conditioner, in all likelihood there's already someone in your area looking to offload an old unit. There's no need to travel far or pay exorbitant shipping costs to get a heavy piece of hardware delivered to your door. Plus, money spent locally tends to stay local, so you’re also helping your community.

We recommend SearchTempest, which compiles listings from local sources such as Craigslist and Facebook Marketplace, as well as eBay and Amazon. Keep in mind that ACs purchased this way typically don't come with warranties. You’ll also have to do your own work to vet the sellers and arrange a pickup.

When you’re buying a used AC, you’ll want to make sure you’re getting a machine that actually keeps you cool without running up the electric bill or causing other problems for your home or health.

The main thing to remember: Don't buy anything that's more than 10 years old.

Back in 2014, the US Department of Energy implemented new regulations that required most standard-size room air conditioners to achieve a minimum combined energy efficiency ratio (CEER) of 11.0. An AC with that efficiency level will still use close to 40% more energy annually than our top AC pick, from Midea, which has a CEER of 15.0. Based on current energy prices, that difference could cost you about $16 more per year on average. That's ultimately not a bad trade-off for buying used! But the further back you go before those standards were in place, you’ll find that AC efficiency swiftly declines, which means even more noise and higher energy bills.

Older ACs—particularly those made before 2010 (PDF)—are also more likely to use hydrochlorofluorocarbon (HCFC) refrigerants like HCFC-22 (also known as R-22). While these are arguably preferable to the older refrigerants that helped bore a hole in the ozone layer, HCFCs still aren't great for the planet, and they have an extremely high global warming potential. As a result, some common HCFCs have also been illegal (PDF) to produce within or import to the United States since 2020 (with the rest to follow in 2030). This could pose some problems if you ever need a refrigerant refill. Most ACs will have the refrigerant type listed on a label on the side of the machine. If you can't figure out how old the air conditioner is, or the seller doesn't know when they bought it, you should at least try to make sure it doesn't use R-22.

Be sure the AC fits your window. Most window air conditioners have expandable plastic side panels, which are meant to fill the width of your window and keep cooled air in. Unfortunately, they are prone to breaking; that could make it more difficult to get an airtight seal (and you could lose all that air you just cooled). If you don't have hung windows (the kind that slide up and down), you may need to go for a portable air conditioner. These ACs are typically less efficient than window units and take up more space inside your home, but they offer more-flexible installation options.

Make sure you’re getting enough power. The AC unit should have the right power load to cool the size of the room. In most situations—like to cool a 200- to 400-square-foot room—a 6,000- or 8,000-Btu unit should do the trick. If you get a bigger AC than you need, it will still cool the room, but it won't dehumidify it properly, leaving you feeling cold, damp, and clammy. Still, that's preferable to an undersize AC, which will run up your electric bill without providing any relief from the heat. If you’re not sure which size AC you need, the EPA's Energy Star program has a handy chart to help you out.

Always check the filter. Every air conditioner has an air filter, and it should be easy to remove and clean. Take a peek at it before you buy a unit. A filthy filter isn't a dealbreaker on its own; a little soap and elbow grease should take care of normal dust and gunk. But if you see or smell something funky—such as mold, ash, mildew—it could be a sign that something worse is festering inside the machine.

Ask about warranties (just don't expect to get one). Most new air conditioners come with a warranty that lasts for only a year or two, and it typically isn't transferable to a secondhand buyer. But it doesn't hurt to ask the seller, especially if you’re buying from a professional used-appliance dealer. Some sellers, such as BackMarket, offer warranties on refurbished products. Of course, they might also charge you more than that random dude on Craigslist. Sometimes that's the trade-off.

Watch out for ice. Aren't air conditioners supposed to make things cold? Yes, but the machine shouldn't get so cold that ice or frost starts forming on the hardware. If you see this, it's a sign of a refrigerant leak. And that spells trouble. A leak will affect the efficiency of your AC—so it might not cool the air at all—and it could be toxic and harm you or the environment.

Don't buy a unit with a discolored control panel. If an AC's control panel (on the front) has yellowed (or browned, or greened), there's a chance you could be bringing some nasty stuff into your home. (The least-worst reason for any yellowing would be that the unit is more than 10 years old, so you probably shouldn't be using it anyway.) Remember, you’re going to be breathing the air this thing puts out. And that includes whatever smoke, must, or mildew is still trapped inside of it. (If you see dirt or discoloration on the part of the AC that sits outside the building, that's normal.)

Sharp edges could be a dealbreaker. Air conditioners are hefty machines that can handle a few dings and dents. You can probably deal with some broken plastic pieces on the front grille, too. But if the metal chassis is beat up enough that it has cracks or kinks, you may want to leave it alone. They could affect the seal around the window or the flow of air inside the unit, or they could create ventilation or filtration problems.

The exceptions to the sharp-edge rule are those metal exhaust fins on the back of the unit. They are supposed to be sharp. But they can get flattened, bent, or collect gunk and debris. If that happens, it's an easy fix. Just scrub them clean with a wire grill brush or a can of compressed air, or carefully twist the blades back into shape, and the air will be flowing normally in no time.

This article was edited by Katie Okamoto and Harry Sawyers.

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