02 / WINDOWS
The best window air conditioner covers for winter
A window unit left in over winter is a hole in the wall with a fan in it. Covering the indoor face helps. Dealing with the concertina side panels helps more, and almost nobody does it.
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Buy an INDOOR cover, not an outdoor one — the indoor face is where cold air enters the room. Better still, deal with the plastic accordion side panels either side of the chassis, which leak more than the machine does. Best of all, if you can lift it out, take the unit out for the winter.
Why a window unit is such a bad winter draft
A window air conditioner is not a sealed appliance sitting in a sealed hole. It is a box with a fan and a heat exchanger, mounted through the wall of your house, with deliberate openings on the outdoor side and a chassis that was never designed to be airtight. Around it, filling the rest of the window opening, are two thin plastic panels that concertina out to whatever width is needed.
In August none of that matters. In January every part of it is a path: through the unit's own vents and coil housing, around the chassis where it sits on the sill, and through and around the side panels. The sash resting on top of the unit does not seal either, because it is resting on a machine rather than closing onto a frame.
The result is one of the largest single air leaks a house can have, and it is a leak most people walk past because the appliance looks like it belongs there.
Indoor cover or outdoor cover
This is the only decision that really matters and the listings make it needlessly hard. Search for a window AC cover and you will get both kinds, described in similar language, at similar prices.
- Outdoor covers go over the part of the unit outside the building. They keep rain, snow and leaves out of the coil and off the fan. They are genuinely useful for the machine's lifespan. They do almost nothing for the draft, because the air reaching your room has already got past the chassis on the inside.
- Indoor covers go over the face of the unit inside the room. They block the path from the unit into the room, which is the path you actually feel. This is the kind that makes a room warmer.
- Surround panels replace or insulate the concertina side panels. They address the part of the installation that leaks most and the one no face cover touches.
Match the part to your gap
Measure at the widest point. Then read across. If your measurement sits on a boundary, take the larger band — a seal that is slightly too big compresses, and one that is too small does nothing at all.
| Your gap | Part type | Our pick | Price |
|---|---|---|---|
| Unit stays in year-round | Insulated surround side panels |  Breeze Stop Surround Insulation Side Panels for Window AC UnitsReplaces the flimsy accordion panels, which are the actual leak. Published for winter and summer, so the unit stays usable. | $32.99 · CHECK ON AMAZON |
| Large unit, out of use all winter | Indoor insulated face cover |  Jeacent Indoor Air Conditioner Cover, Double Insulation, LargeCovers the indoor face, which is the side the cold air enters the room from. | $19.99 · CHECK ON AMAZON |
| Standard unit, out of use all winter | Indoor insulated face cover | Jeacent Indoor Air Conditioner Cover, Double Insulation, SmallSame cover in the smaller published size. Measure the face of the unit rather than guessing. | $17.99 · CHECK ON AMAZON |
| You want to match dimensions exactly | Dimensioned indoor cover |  Window Air Conditioner Cover for Inside, 21 in W x 15 in H x 3.5 in DPublishes width, height and depth, which makes the fit question answerable before you buy. | $19.99 · CHECK ON AMAZON |
Measure the face, not the window
Covers in this category are sold either by a rough size label — small, large — or by published dimensions. The dimensions are worth hunting for, because the fit question is binary: a cover that does not close around the unit leaves a gap, and a gap is what you were trying to remove.
Three numbers to take before you buy: the width of the unit's indoor face, its height, and how far it protrudes into the room from the sash. That last one catches people out — a cover sized on width and height alone will not sit flat against a unit that sticks four inches into the room.
The picks
Quick picks
Ranked for fit, not for hype. Tap a row to jump to the full write-up, or go straight to the listing.
| # | Product | Best for | Gap range | Price |
|---|---|---|---|---|
| 1 | Breeze Stop Surround Insulation Side Panels for Window AC UnitsThe one product here that addresses the concertina side panels rather than the machine — which is where most of the cold air around a window unit actually gets in. | The gap every cover misses | Not published as a gap range — panels sized to the unit surround | $32.99 · CHECK ON AMAZON |
| 2 | Jeacent Indoor Air Conditioner Cover, Double Insulation, LargeThe same cover in the larger published size, for the units the small one will not close over. | A bigger window unit | Not published as a gap range — sold by unit size | $19.99 · CHECK ON AMAZON |
| 3 | Jeacent Indoor Air Conditioner Cover, Double Insulation, SmallThe indoor cover done properly: it goes over the inside face of the unit, which is where the cold air is actually coming into the room. | A standard window unit, indoors | Not published as a gap range — a fitted cover, sold by unit size | $17.99 · CHECK ON AMAZON |
| 4 | Window Air Conditioner Cover for Inside, 21 in W x 15 in H x 3.5 in DThe pick for anyone who would rather match three published numbers than trust the words small and large. | Buying on actual dimensions | Not applicable — published as fitted dimensions | $19.99 · CHECK ON AMAZON |
| 5 |  3M Indoor Window Insulator Kit, Two PackThe two-window box: the right way to find out whether film solves your problem before committing a whole house to it. | Trying it on one room | Two windows up to a published 3 ft x 5 ft each | $9.48 · CHECK ON AMAZON |
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The gap every cover misses
Breeze Stop Surround Insulation Side Panels for Window AC Units
Published gap range
Not published as a gap range — panels sized to the unit surround
#ad · how we are funded · price as of October 17, 2026
The one product here that addresses the concertina side panels rather than the machine — which is where most of the cold air around a window unit actually gets in.
Where the number comes fromEvery window air conditioner ships with thin plastic accordion panels filling the window either side of the chassis. They are the weakest part of the whole installation and no face cover touches them. These are insulated replacements for that surround. Published for winter AND summer use, so unlike a cover it does not have to come off to run the unit.
- Targets
- The accordion side panels, not the unit face
- Published seasons
- Winter and summer
- Side fitted
- Indoor
- Finish
- White
- Published R-value
- None claimed
- Mounting
- Fitted into the window either side of the AC chassis
What it does well
- Attacks the actual weak point of a window AC installation instead of the machine
- Published for year-round use, so the unit stays usable
- Complements rather than duplicates a face cover
Where it fails
- Costs more than a simple face cover while leaving the face uncovered
- Fit depends on your window width and the chassis position
- Does not help at all if your unit comes out for the winter
Who this is forA window unit that stays in year-round, with flimsy factory side panels.
A bigger window unit
Jeacent Indoor Air Conditioner Cover, Double Insulation, Large
Published gap range
Not published as a gap range — sold by unit size
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The same cover in the larger published size, for the units the small one will not close over.
Where the number comes fromIdentical construction to the small, in Jeacent's larger published size. The sizing is the only decision: a cover that does not close fully around the face leaves the air path it was bought to block.
- Side fitted
- Indoor
- Construction
- Double insulation, per Jeacent
- Sizing
- Large
- Published R-value
- None claimed
- Seasonal
- Winter only
- Mounting
- Fitted over the indoor face of the window unit
What it does well
- Fits the larger units that the small size leaves gaping
- Same honest absence of an invented R-value
- Indoor-side fitting, so it addresses the draft rather than the weather
Where it fails
- Still does nothing for the perimeter gap around the chassis
- Winter-only part that has to be stored
- Large/small sizing is coarse for a category where fit is everything
Who this is forA larger window unit that a small cover will not close around.
A standard window unit, indoors
Jeacent Indoor Air Conditioner Cover, Double Insulation, Small
Published gap range
Not published as a gap range — a fitted cover, sold by unit size
#ad · how we are funded · price as of October 17, 2026
The indoor cover done properly: it goes over the inside face of the unit, which is where the cold air is actually coming into the room.
Where the number comes fromThis is an INDOOR cover. That distinction decides whether the product does anything for a draft: an outdoor cover protects the machine from weather, while an indoor cover blocks the air path through the machine into the room. Jeacent publishes this in a small and a large; measure the face of your unit rather than guessing.
- Side fitted
- Indoor
- Construction
- Double insulation, per Jeacent
- Sizing
- Small (a large is also published)
- Published R-value
- None claimed
- Seasonal
- Fitted for winter, removed in summer
- Mounting
- Fitted over the indoor face of the window unit
What it does well
- Covers the indoor face, which is the side that matters for a draft
- Jeacent publishes two sizes rather than one universal fit
- No R-value invented for it, which is the honest position for a fabric cover
Where it fails
- A cover over the unit does nothing about the gap around the CHASSIS, which is usually the bigger leak
- Has to come off before the unit is used, so it is a winter-only part
- Published sizing is small/large rather than dimensions, so measure and expect to check
Who this is forA window air conditioner staying in the window all winter, in a room you are heating.
Buying on actual dimensions
Window Air Conditioner Cover for Inside, 21 in W x 15 in H x 3.5 in D
Published gap range
Not applicable — published as fitted dimensions
#ad · how we are funded · price as of October 17, 2026
The pick for anyone who would rather match three published numbers than trust the words small and large.
Where the number comes fromThe listing publishes 21 in wide by 15 in high by 3.5 in deep. That is the most useful thing a cover in this category can publish, because the whole job depends on the cover closing over the unit's face. Measure your unit's width, height and how far it protrudes into the room, then match.
- Published width
- 21 in
- Published height
- 15 in
- Published depth
- 3.5 in
- Side fitted
- Indoor
- Finish
- Beige
- Mounting
- Fitted over the indoor face of the window unit
What it does well
- Publishes all three dimensions, which makes the fit question answerable before you buy
- A larger 25 x 17 in version is listed for bigger units
- Beige is less conspicuous in a living room than white or black
Where it fails
- Fixed dimensions mean a unit between sizes is not served
- Same perimeter-gap limitation as every face cover
- Unbranded reseller listing rather than an established maker
Who this is forSomeone who has measured their unit and wants a cover that matches it.
Trying it on one room
3M Indoor Window Insulator Kit, Two Pack
Published gap range
Two windows up to a published 3 ft x 5 ft each
#ad · how we are funded · price as of October 17, 2026
The two-window box: the right way to find out whether film solves your problem before committing a whole house to it.
Where the number comes from3M publishes the window count and nominal window size. No gap figure applies to film.
- Windows covered
- 2
- Per window
- 3 ft x 5 ft
- Tape
- Scotch window film mounting tape
- Install
- Indoor
- Use
- Single room trial
- Mounting
- Scotch double-sided tape, hair dryer shrink
What it does well
- Cheap enough to test the idea on the worst room
- Same tape as the five-pack
- Two windows is one evening, not a project
Where it fails
- Worst price per window in the range
- Standard film, so same puncture caveat
- You will end up buying the big kit anyway if it works
Who this is forOne cold room and a reasonable suspicion that film will fix it.
What we would skip, and why
Nobody in this category ever declines to recommend something. That is what makes universal praise worth ignoring. Here is what we would not buy.
An outdoor cover, if your goal is a warmer room
This is the mix-up that wastes the most money in this category. An outdoor cover wraps the part of the unit hanging outside and protects it from weather. It does nothing measurable about the cold air coming into your room, because that air travels through and around the chassis on the inside. If you want the machine protected, buy an outdoor cover. If you want the room warmer, buy an indoor one. They are different products solving different problems and the listings rarely say so.
Any cover at all, if you can take the unit out
The honest first recommendation. A window air conditioner removed for the winter leaves a window that closes and locks like any other, and the whole problem disappears — no cover, no side panels, no compromise. Units are heavy and awkward and many people genuinely cannot do it alone, which is why this page exists. But if you have someone to help you lift it, that is the fix and everything below is second best.
Sealing the unit and ignoring the accordion panels
Every window AC ships with thin plastic concertina panels that fill the window either side of the chassis. They are a few tenths of an inch of unfilled plastic, they never seal properly at the sash, and they are the largest leak in the whole installation. A beautifully insulated cover over the front of the machine leaves both of them untouched. If you are only going to fix one thing, fix these.
Taping the unit up with duct tape for the season
It works for about a month and then you have adhesive residue baked onto a painted sash and a vinyl frame, which is a worse job to remove than the draft was to live with. If you want a temporary seal around a chassis, use rope caulk — it presses into the same gaps, seals at least as well, and peels away cleanly in spring.
How we picked
- We rank on which side of the window the product addresses, because that single fact decides whether it does anything for a draft. Indoor products block the air path into the room. Outdoor products protect the machine. Only the first kind is on this page.
- After that we rank on published fit. A cover that does not close around the unit leaves the path it was bought to block, so a listing that publishes width, height and depth beats one that publishes the words small and large.
- We record where a maker publishes no R-value and treat that as the honest position rather than a gap — an insulated fabric cover has no meaningful R-value to quote, and the ones that invent a number are the ones to distrust.
- None of this is tested by us; the method is published in full.
We have not tested these products and we do not claim to have. The full method, including what we refuse to claim, is on how we pick.
Complete the kit
The parts that decide whether the seal you just bought actually holds. Skip these and you will be doing the job again in March.
Seasonal window sealing
Frost King B2 Mortite Fingertip Caulking Cord, 1/8 in x 90 ft
Rope caulk: pliable putty you press into a gap in October and peel out in April, leaving no adhesive behind.
Large, irregular gaps
fowong Open Cell Foam Weather Stripping, 1 in x 1/2 in x 13 ft
Half-inch-thick open-cell foam for the gap nothing else reaches — an AC surround, a loose sash, a warped frame.
Removing old weatherstrip adhesive
Goo Gone Pro-Power Adhesive Remover Spray, 16 fl oz, with Scraper
The step everybody skips: the new tape will not stick to the residue the old tape left behind.
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The gap a cover cannot reach
Even with the best indoor cover fitted and good surround panels, one path remains: the joint where the chassis rests on the sill and where the lowered sash meets the top of the unit. Those are irregular, they are different on every installation, and no molded product fits them.
Rope caulk is the answer, for the same reason it is the answer on an old sash window. It is a putty rope you press into whatever shape the gap happens to be, it seals well, and it peels off in spring without marking the paint. A single pack does the perimeter of a window unit several times over. It is in the kit above, and the fuller comparison is in rope caulk vs V-seal vs film.
If the unit is out of use entirely and the window it occupies is one you are happy to lose until spring, the most complete fix is to remove the unit, close the window, and treat it like any other cold window — which puts you back in how to seal windows for winter.
Questions people actually ask
- Should I cover my window air conditioner inside or outside?
- Inside, if the goal is a warmer room — the indoor face is where cold air enters. Outside, if the goal is protecting the machine from weather. They are different products and many listings are not clear about which they are. Covering both is reasonable if the unit is staying in and out of use.
- Is it better to remove the window AC for winter?
- Yes, clearly, if you can lift it. A removed unit means a window that closes and locks normally, and every draft problem in this category disappears with it. Covers exist because units are heavy and awkward, not because they are the better answer.
- What leaks most on a window air conditioner?
- The plastic accordion side panels that fill the window either side of the chassis. They are thin, unfilled and never seal well at the sash. A cover over the front of the machine leaves them completely untouched, which is why insulated surround panels do more for a draft than a face cover does.
- Do window AC covers have an R-value?
- The honest ones do not claim one. An insulated fabric cover has no meaningful, testable R-value, and none of our picks publishes a figure. Treat any listing that does quote an R-value for a fabric cover with suspicion, and judge these products on fit and coverage instead.
Read next
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Rope caulk, V-seal or film: three ways to seal a window
Three ways to seal a window, decided by one question: does it still have to open?
Draft fixes for renters that leave no trace
Rope caulk, stoppers and removable film — the fixes that come out clean at move-out.