Introduction
Hey there — Jake Lawson here. Installing a through-the-wall air conditioner is one of those home improvement tasks that looks simple at first glance. Cut an opening, slide in a sleeve, pop in the unit, and enjoy the cool air.
But if you’ve ever tackled one before, you probably know it’s rarely that simple. A successful installation depends on choosing the right tools, carefully preparing the wall, ensuring a level fit, proper sealing — and that’s before you even touch the electrical.
And here’s the million-dollar question most homeowners ask me all the time: Should I do this myself or hire a pro?
In this guide, we’ll look at the whole picture — breaking down the DIY process, where homeowners most often trip up, and when calling a professional is the smarter (and more cost-effective) move. Ready to dive in? Let’s go.
The Basics of Installing a Through-the-Wall AC
Before we tackle whether you can do this yourself, let’s look at what’s involved. Installing a through-the-wall air conditioner typically requires:
✅ Measuring and marking the perfect cutout for the sleeve.
✅ Removing drywall or paneling and cutting into exterior wall materials (brick, siding, concrete).
✅ Framing the opening with supports so the unit is stable.
✅ Installing a metal wall sleeve, making sure it’s level and pitched slightly outward for drainage.
✅ Sealing gaps with insulation and exterior flashing to prevent leaks.
✅ Wiring the unit, often to a dedicated electrical circuit, to prevent overloads.
✅ Finally, sliding the air conditioner into the sleeve and testing it.
Each of those steps can go smoothly — or they can go sideways quickly without the right tools or knowledge.
DIY Installation: What You Need to Know
For handy homeowners with some experience, tackling a through-the-wall AC can be a rewarding weekend project. Let’s look at the key things you’ll need to do to make it successful.
📐 Getting the Right Measurements
Before cutting into anything, make sure you have the exact dimensions of your AC unit and sleeve. Follow the manufacturer’s specs precisely — the hole must fit snugly, allowing enough space for proper flashing and insulation.
And don’t forget to check what’s inside the wall — electrical wires, plumbing, and studs may need to be relocated before you cut. Using a wall scanner or similar tool can help you spot hidden obstacles.
🧰 The Tools
You’ll need some serious tools for this project:
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Reciprocating saw or concrete saw
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Cordless drill and driver bits
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Level
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Measuring tape and framing square
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Insulation, flashing, and sealant
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Safety gear (goggles, gloves, dust mask)
If you’re missing these, you’ll need to rent or buy them — and that’s an added cost you need to plan for.
🔧 Installing the Sleeve and AC Unit
This is where things get tricky. The sleeve is what supports the unit and directs water drainage. Installing it requires proper framing inside the wall cavity and mounting the sleeve with a slight tilt (1/4-inch per foot) so water drains outside. Get this wrong and you can end up with water leaking into your walls or under your flooring — leading to serious water damage or mold over time.
As a pro, I can’t stress this enough: if the sleeve isn’t installed correctly, the entire AC unit will never work efficiently.
🔌 Wiring the Unit
If your unit is 220V or 240V — which most larger units are — you’ll need a dedicated electrical circuit. Adding a new outlet or running wires back to the panel usually requires an electrician. Even smaller 115V units sometimes need dedicated circuits to prevent tripping breakers.
⚡ Always cut power at the breaker before starting any wiring. If you’re not comfortable with this step, it’s time to call in a pro.
When DIY Makes Sense
If you already have a pre-existing sleeve and the right power outlet installed — you’re just swapping the unit — then yes, this is an easy DIY job. Or if you’re experienced with framing, wiring, and exterior sealants and feel comfortable making a clean, weatherproof installation, you can do this yourself.
But remember that a botched job can lead to water infiltration, electrical hazards, or higher energy bills due to poor sealing and insulation. That’s where the value of a pro really comes in.
Why Hiring a Pro Could Save You Time and Money
There are plenty of good reasons to hire a licensed HVAC pro or contractor for this job:
🏅 Experience and Expertise
A pro can look at your wall, spot any surprises, and know instantly what needs to happen. From proper framing to perfecting that drain slope, this is routine for them — meaning less guesswork and fewer mistakes.
💸 Cost Considerations
Sure, you’ll pay more up front for labor — typically $200 to $500, depending on complexity and region (source: HomeAdvisor AC Installation Costs). But that upfront investment can pay off:
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No need to buy or rent specialized tools.
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No trial-and-error damage to your home.
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Proper insulation and sealing = lower long-term energy bills.
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Peace of mind that the electrical is up to code — a huge safety issue that also matters for insurance purposes.
🕒 Save Time
A pro can often install a unit in a matter of a few hours, especially if they specialize in HVAC and have all tools and materials ready to go.
If you attempt this yourself on a weekend, be prepared for multiple trips to the hardware store — and potentially leaving a hole in your wall overnight if things don’t go as planned.
Red Flags That Mean “Hire a Pro”
Here are a few clear signs that this is not a good DIY project:
❌ Cutting into brick, concrete, or stone walls.
Masonry is a different game — you’ll need specialized tools like a concrete saw or rotary hammer. Mistakes here can mean expensive structural repair.
❌ No existing power source nearby.
If you need new electrical outlets or a dedicated 240V circuit, leave this to a licensed electrician. Poor wiring is a serious fire hazard (source: NFPA Electrical Fire Safety).
❌ Structural questions.
If you have any doubt about your wall’s load-bearing status or what’s inside it (pipes, wires), you’ll want a pro involved.
❌ Waterproofing concerns.
If you live in a rainy climate or your exterior walls see a lot of water exposure, improper flashing and sealing can cause serious water infiltration and damage over time.
(source: This Old House on Flashing Techniques)
Maintenance and Warranty Considerations
One overlooked benefit of a professional installation? Warranty compliance. Many AC manufacturers require a licensed pro to do the installation for the warranty to stay valid. Installing it yourself — especially if it involves electrical work — might void the warranty if there’s ever an issue.
And after installation, a pro will check refrigerant levels, drainage, and overall performance before leaving. That’s the kind of safety check that can prevent a surprise service call a few months later.
What It Costs to Hire a Pro
You’ll usually pay between $200 and $500 for a straightforward installation into an existing opening. Creating a new wall opening? Expect more — especially if there’s electrical or masonry work involved.
More complex jobs could run $500 to $1,000 or more.
(source: Angi AC Installation Estimates)
That might sound steep at first, but when you compare it to the cost of water damage repair, rewiring, or even voiding your AC’s warranty — it looks like a solid investment.
DIY Success Tips (If You Go That Route)
Still feeling good about tackling this yourself? Here are a few pro tips to improve your odds:
✅ Measure twice, cut once.
Double-check all dimensions before cutting your opening.
✅ Create a strong frame.
Use 2x4s or metal framing and secure them properly — the AC unit can weigh over 100 pounds.
✅ Keep it level — with a slight tilt.
Your sleeve must lean ever so slightly outside to allow for drainage.
✅ Seal thoroughly.
Use flashing tape, caulk, or spray foam insulation to close any gaps — especially at the exterior.
✅ Test before closing up.
Run the unit and check for vibrations, water drainage, and power issues before sealing the wall permanently.
Conclusion: DIY or Pro?
At the end of the day, choosing to DIY or call a pro for a through-the-wall AC installation is all about your skill level, tools, and the complexity of the job.
If you have experience framing walls, running electrical, and sealing exterior openings — go for it. But if you’d rather not gamble with water damage, electrical safety, or voiding your unit’s warranty, it’s worth the price of a professional.
And whether you do it yourself or hire a pro, don’t cut corners on your AC unit choice. Our Through-the-Wall Air Conditioners pillar page at The Furnace Outlet has the top brands and models to suit every space and budget — all built for easy installation and years of trouble-free cooling.
