Can You Put Security Bars on Windows with Air Conditioners?

Yes, you can install security bars on windows with air conditioning units. Telescopic bars like the SWB Model A (~$90) mount around the AC unit rather than across it, securing the exposed glass area above and beside the air conditioner without blocking airflow or interfering with cooling performance.

This is one of the most common questions homeowners and apartment renters ask about window security. Roughly 43 million homes in the United States use window air conditioning units, according to the U.S. Energy Information Administration's Residential Energy Consumption Survey. Most of those window AC units are installed in ground-floor or second-floor windows, which are exactly the windows most vulnerable to break-ins. The concern is real: a window with an AC unit has a built-in gap in its security, and burglars know it.

Here's how to secure windows that have air conditioners installed, what products work, and what mistakes to avoid.

Why Windows with AC Units Are Security Vulnerabilities

A window air conditioner creates a security problem in two ways that most homeowners don't think about until it's too late.

The Push-In Attack

Most window AC units are held in place by gravity, a few screws into the window sash, and the closed window resting on top of the unit. From outside, a burglar can push the AC unit inward (or pull it outward) with moderate force, creating an opening large enough to climb through. Standard installation brackets and L-angle supports are designed to prevent the unit from falling out accidentally. They are not designed to resist a deliberate push-in attack by someone applying 100-200 pounds of force.

According to the New York City Police Department's crime prevention guidance, window AC units are a known entry vector in ground-floor apartments. The NYPD specifically recommends that residents secure the window area around the AC unit with a physical barrier.

The Gap Problem

When a window AC unit is installed in a standard double-hung window, the lower sash is raised to accommodate the unit. The space between the top of the AC unit and the upper window frame is filled with accordion-style side panels (the foam or plastic extensions that come with the unit). These panels provide zero security. A burglar can punch through them with a fist, reach through to unlock the window, or simply push the entire panel inward. There's also often a gap above the lower sash where it sits on top of the AC unit. None of these are structural barriers.

The Signal to Burglars

A visible window AC unit tells a burglar three things: (1) this window opens, (2) it has a built-in weak point, and (3) the occupant likely hasn't invested in serious window security. Criminological research consistently shows that burglars look for the path of least resistance, and a window with an AC unit and no security bars is about as low-resistance as it gets.

How Telescopic Bars Work Around AC Units

The solution isn't removing your air conditioner or giving up on window security. It's using bars designed to work around the unit.

The Telescopic Advantage

Telescopic window security bars, like the SWB Model A, extend and retract to fit a range of window widths. This adjustability is what makes them ideal for AC windows. Instead of installing a single bar assembly across the entire window (which would block the AC unit), you install bars in the sections of the window that aren't occupied by the air conditioner.

Configuration Options

Depending on your window type and AC unit position, there are several ways to configure telescopic bars:

Configuration 1: Bars above the AC unit. In a standard double-hung window where the AC sits in the lower sash opening, the upper portion of the window (above the AC unit) is the most vulnerable area. Install a telescopic bar assembly across this upper section. This covers the gap between the top of the AC and the upper window frame, which is the area most commonly exploited for push-in entry.

Configuration 2: Bars on both sides of the AC unit. If your AC unit is centered in the window and there's exposed glass on either side, you can install narrow bar sections on both sides. The SWB Model A's telescopic range accommodates narrow widths that fixed-size bars can't cover.

Configuration 3: Full coverage with AC cutout. Some installations use a full window bar assembly with a notched section that allows the AC unit to protrude through. This provides maximum coverage but requires more precise measurement and may need a custom bracket arrangement. For detailed measurement instructions, see our guide to measuring windows for security bars.

Maintaining Airflow

A critical concern is that the security bars must not block the AC unit's air intake or exhaust. Window air conditioners pull warm air from outside through rear vents and expel condensed moisture through the back. If bars are positioned too close to the rear of the unit, they can restrict airflow and reduce cooling efficiency.

The SWB Model A's vertical bar design naturally avoids this problem because the bars run parallel to airflow rather than across it. Air moves freely between vertical bars. As long as the bars don't physically press against the AC unit's housing, there's no airflow restriction.

Installation Options for AC Windows

Here's a step-by-step approach to installing security bars on a window with an AC unit already in place.

Step 1: Measure the Exposed Areas

With the AC unit installed, measure the dimensions of each exposed section of the window. You'll typically have:

• An upper section above the AC unit (width of window x height of upper gap)
• Side sections if the AC unit doesn't span the full window width
• The area covered by the accordion side panels (these need bars behind them)

Step 2: Secure the Accordion Panels

Before installing bars, reinforce the accordion side panels. These flimsy panels are the weakest point. You can:

• Replace them with rigid plexiglass or sheet metal cut to size
• Install security bars behind them so that even if the panel is punched through, steel bars prevent entry
• Use foam backer rod and screws to fix the panels rigidly to the window frame rather than leaving them loose

Step 3: Install Frame-Mount Bars

Using the SWB Model A's frame-mount brackets, install bars across the exposed sections of the window. The telescopic adjustment allows each bar to be extended to precisely fit the available width. Secure the brackets to the window frame with the included hardware.

Step 4: Lock the Window Sash

The window sash sitting on top of the AC unit can be pushed up by a burglar to create additional entry space. Prevent this by installing window sash locks or pins that prevent the sash from being raised from outside. A simple solution is drilling a small hole through the inner sash frame into the outer sash and inserting a nail or pin.

Step 5: Secure the AC Unit Itself

The AC unit should be anchored so it can't be pushed in or pulled out:

• Use a heavy-duty mounting bracket screwed into the window frame (not just resting on the sill)
• Install an L-bracket at the top of the AC unit connecting it to the upper window frame
• Consider a security cage around the exterior portion of the AC unit (available for about $30-$60)

What About AC Unit Theft?

Beyond the break-in risk, window AC units are also theft targets themselves. A working window air conditioner sells for $150-$400 new, and even used units have value. In urban areas, AC unit thefts spike during summer months.

Security bars help prevent AC theft in two ways:

1. Physical barrier: Bars installed around the AC unit make it significantly harder to pull the unit out from outside.
2. Deterrent signal: A window with visible security bars signals that the homeowner takes security seriously, discouraging both break-in attempts and property theft.

For the best protection against AC unit theft specifically, combine security bars with a dedicated AC lock bracket (a steel plate that bolts through the AC unit's chassis into the window frame) and a window sash lock that prevents the window from being opened wider than the AC requires.

Common Mistakes to Avoid

When installing security bars on windows with air conditioners, these are the errors that compromise security or damage the AC unit.

Mistake 1: Only Securing the Top Section

Many people install bars above the AC unit and call it done. But the accordion side panels remain vulnerable, and the AC unit itself can be pushed in. Full security requires covering all exposed areas and anchoring the AC unit.

Mistake 2: Bars That Block the AC Unit's Rear Vents

Installing bars flush against the back of an AC unit restricts airflow, reduces cooling capacity, and can cause the compressor to overheat and fail prematurely. Maintain at least 4-6 inches of clearance between any bar and the AC unit's rear housing.

Mistake 3: Using Pressure-Mount Bars

Pressure-mounted bars (like tension rods) that wedge into the window frame without screws are not genuine security. A firm push from outside can dislodge them. Always use bars that are mechanically fastened to the frame with screws or bolts. The SWB Model A uses a frame-mount bracket system with anti-tamper hardware.

Mistake 4: Forgetting About Seasonal Changes

If you remove your AC unit in the fall and winter, you need a plan for the full window. Either leave the security bars installed year-round (adjusting them to cover the full window when the AC is removed) or have a second set of bars sized for the full window opening. The Model A's telescopic design helps here, since the same bars can be adjusted to a wider setting when the AC unit is taken out.

Mistake 5: Ignoring Fire Egress

If the window with the AC unit is in a bedroom or serves as a fire escape route, the security bars must have a quick-release mechanism. A window blocked by both an AC unit and fixed bars creates a potentially deadly fire trap. For egress-required windows, see our coverage of fire code compliance for window bars.

Alternative Solutions for AC Window Security

While telescopic security bars are the most effective solution, there are other options worth considering depending on your budget and situation.

AC Security Brackets

Purpose-built metal brackets that bolt through the AC unit's chassis and screw into the window frame. These prevent the unit from being pushed in or pulled out but don't protect the window glass area around the unit. Cost: $20-$50.

Window Sash Locks

Pins, bolts, or clamp-style locks that prevent the window sash from being raised beyond the AC unit's position. These are a good supplement to bars but don't provide physical protection against glass breaking or panel punching. Cost: $5-$15.

Plexiglass Panel Replacements

Replacing the flimsy accordion panels with rigid polycarbonate panels screwed into the window frame. This closes the easy push-through vulnerability but doesn't provide the forced-entry resistance of steel bars. Cost: $15-$30 in materials.

The Best Approach: Layer Everything

The strongest setup combines multiple measures: SWB Model A bars across all exposed glass and panel areas (~$90), a dedicated AC mounting bracket ($20-$50), window sash locks ($5-$15), and rigid panel replacements ($15-$30). Total investment: approximately $130-$185 for a complete, layered defense that addresses every attack vector. Compare that to an average burglary loss of $2,661 and the math is straightforward.

Frequently Asked Questions

The Bottom Line

A window air conditioner doesn't have to be a security liability. With the right approach, you can keep your home cool and secure at the same time. Telescopic security bars like the SWB Model A are specifically designed for situations like this, adjusting to fit the exposed window sections around your AC unit and mounting solidly to the window frame with anti-tamper hardware.

The cost is about $90 for a bar that covers the most vulnerable section of the window. The alternative is a window that any reasonably determined burglar can breach in under 30 seconds. That's not a hard calculation.