I’ve spent decades working with PTAC units — in homes, apartments, commercial spaces, and especially hotels. And if there’s one thing I can tell you with 100% confidence, it’s this:
👉 Hotels understand system sizing better than anyone.
They have to.
Hotels deal with:
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dozens or hundreds of rooms
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unpredictable guest behavior
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wildly different room exposures
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constant occupancy
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the hottest days, coldest nights, biggest humidity swings
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and online reviews that depend heavily on room comfort
A hotel can’t afford to guess. They can’t afford undersized units that struggle, or oversized units that short-cycle. They size systems with a precision that most homeowners never even think about.
Today, I’m going to show you the exact strategies hotels use to size their PTACs — and how you can apply these professional techniques to your own home, condo, or rental.
Amana J-Series PTAC Model 17,000 BTU PTAC Unit with 5 kW Electric Heat
By the time you’re done reading, you’ll understand:
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why hotels rarely get sizing wrong
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what they evaluate that homeowners ignore
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how to size like a pro
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and how to avoid the most common mistakes in system sizing
Let’s dive in.
🏨 1️⃣ Why Hotels Treat System Sizing Differently Than Homeowners
Hotels live and die by comfort.
If Room 423 is too hot?
Guest goes downstairs. Refund. Bad review.
If Room 317 is too cold?
Maintenance call. Unhappy guest. Another refund.
Now multiply that by:
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200 rooms
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365 days a year
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thousands of guests
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peak summer conditions
Hotels can’t guess their HVAC loads — they rely on precision.
🧠 Hotels have performance data homeowners never see.
Hotels know:
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which floors run hottest
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which rooms get afternoon sun
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which rooms always run colder
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how occupancy changes loads
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how sun exposure affects cycles
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what humidity does to cooling demand
Homeowners?
Most only look at square footage.
Hotels look at:
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orientation
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window count
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shading
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occupancy patterns
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heat load
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humidity
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floor height
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outdoor temperature extremes
This data-driven approach is why hotels almost never install a badly sized system.
🌦️ 2️⃣ Hotel Rule #1: Size for the Worst Day — Not the Average Day
This is the #1 thing homeowners miss.
Most people size HVAC by looking at:
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average summer temps
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average winter lows
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average humidity
Hotels don’t care about the average.
They size for the worst 5% of conditions, because that’s where comfort failures happen.
🥵 In summer:
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peak sun exposure
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90–100°F outdoor temps
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humidity over 70%
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full occupancy
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guests showering, using hair dryers, running electronics
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housekeeping cycles opening/closing doors
🥶 In winter:
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temperatures dropping rapidly at night
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large heat loss through windows
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freeze drafts and wind chill
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strong heat pump drop-off
Hotels build systems that can handle these extremes without breaking a sweat.
Homeowners?
They often size for “typical” conditions… and then the system fails on the days they actually need it.
🌞 3️⃣ Hotels Track Sun Exposure, Window Direction & Floor Height Like Their Comfort Depends On It (Because It Does)
In HVAC, sun exposure is one of the biggest — and most ignored — factors in real-world performance.
Hotels never make that mistake.
☀️ West-facing rooms
Hottest rooms in the building.
Hotels often increase cooling capacity by 10–20%.
🌅 East-facing rooms
Warm in the morning, stable by afternoon.
🌬 North-facing rooms
Coolest rooms — also lose the most heat in winter.
🌇 High floors
Heat rises — top floors are almost always warmer.
🧊 Corner rooms
Two exterior walls = greater heat gain & heat loss.
Hotels document this information for every room.
Homeowners almost never consider it.
Hotels have learned that:
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a 350 sq ft room on the west side may need 30% more cooling
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the same room on the east side may need less
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north-facing rooms need bigger heat kits
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rooms above garages cool fast but lose heat even faster
This level of detail is why hotel PTACs almost always perform well.
For reference, EnergyStar covers how window and solar load affect system performance:
🧮 4️⃣ Hotels Don’t Guess — They Use Actual Room-by-Room Load Calculations
Hotels don’t run their HVAC based on rules of thumb.
They use real load calculations based on:
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square footage
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insulation
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BTU demands
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humidity loads
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window heat gain
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ceiling height
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occupancy
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solar exposure
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usage patterns
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heat bleed from surrounding rooms
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airflow path modeling
Most homeowners use a generic “20 BTUs per square foot” formula — and while that’s a fine starting point, it’s nowhere near enough for complex spaces.
Here’s the simplified version of the hotel method Tony uses in homes:
Step 1: Start with BTUs per sq ft (20 BTU baseline).
Step 2: Add 10–20% for sun-heavy rooms.
Step 3: Add 600 BTUs per additional occupant.
Step 4: Add 15% for corner rooms.
Step 5: Add 20–25% for poor insulation.
Step 6: Adjust for heat kit wattage based on climate.
Hotels do this automatically — which is why they rarely install the wrong unit.
💧 5️⃣ Hotels Size for Humidity — Not Just Temperature
This is the second biggest thing homeowners miss.
Air temperature is easy to control.
Humidity?
That’s the beast.
Hotels understand that cool air without humidity control = uncomfortable air.
Why humidity matters:
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High humidity makes 72°F feel like 78°F
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AC must work harder
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Oversized units short-cycle
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Mold risk increases
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Poor dehumidification = sticky feeling
Hotels use PTAC models with:
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strong latent cooling capacity
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longer, slower cycles
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adjustable fan speeds
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advanced moisture removal modes
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coils optimized for humidity performance
In humid markets like Miami, Orlando, Houston, and New Orleans, hotels prioritize moisture removal over raw cooling BTUs.
Most homeowners just look at the BTU number — and that’s the mistake.
Humidity control is as important as temperature control.
Hotels never forget this. Homeowners often do.
🔥 6️⃣ Hotels Use Higher Heat Kits Because Guest Rooms Lose Heat Faster
Here’s another huge difference:
❄️ In winter, hotels ALWAYS oversize heating wattage.
Why?
Because hotel rooms lose heat fast due to:
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large exterior windows
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curtain setups
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metal framing
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frequent door openings
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poor insulation in older buildings
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wind exposure on high floors
Hotels know that 3.5 kW heat kits aren’t enough for many northern climates.
They install:
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5 kW heat kits in cold climates
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7 kW kits in severe winter regions
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or combined heat pump + resistance setups
You can see why this matters from Energy.gov’s heating performance breakdown:
🔗 https://www.energy.gov/energysaver/heat-pump-systems
Homeowners rarely factor heat loss into sizing.
Hotels treat it as critical.
If your bedroom is:
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north-facing
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above a garage
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full of windows
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located on a top floor
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drafty
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poorly insulated
…then that hotel-sized 5 kW heat kit might be what YOU need, too.
🧑💻 7️⃣ Hotels Always Account for People Heat Load
Most homeowners size purely by square footage.
Hotels know better.
Every person adds ~600 BTUs of heat.
A couple adds 1,200 BTUs.
Kids add movement heat.
Electronics add heat.
Suitcases block airflow.
Work laptops heat the room.
Homeowners often forget that rooms have:
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kids
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guests
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office equipment
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gaming consoles
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pets
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TVs
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streaming boxes
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routers
All of which add heat.
Hotels size their PTACs knowing that rooms are frequently occupied — and occupied rooms generate far more heat than empty ones.
You can see the occupancy BTU factor in EnergyStar guidelines:
🧭 8️⃣ Hotels Predict How Rooms Are Actually Used — Not Theoretically Used
Hotels know EXACTLY how rooms are used:
Morning:
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Guest showers
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Hair dryers
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Steam
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Strong humidity spike
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Heat load from morning sun
Afternoon:
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Direct sun exposure
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Peak cooling demand
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Electronics in use
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Room doors opening/closing
Evening:
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Guests relaxing, watching TV
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Lamps and electronics adding heat
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Cooler outdoor temps
Night:
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Sleeping temperatures drop
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Heat pump struggles in cold climates
Hotels design their systems around usage patterns — not just static conditions.
Homeowners can do the same:
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If you work from home, office heat load matters.
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If you sleep cool, nighttime BTU demand matters.
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If your kids run around, airflow matters.
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If you cook a lot, humidity matters.
Sizing for lifestyle — not just the room — is a hotel secret worth stealing.
🌀 9️⃣ Hotels Use Strategic Airflow Positioning — Not “Wherever It Fits”
Hotels ALWAYS put PTAC units:
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under the window
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near the exterior wall
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where hot and cold air naturally exchange
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where air circulates easily
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away from door drafts
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facing the bed for even comfort
They do this to:
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counteract window heat gain
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improve dehumidification
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promote full-room circulation
Homeowners often install units:
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where the outlet is
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where it’s easiest
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where they can hide it
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where furniture allows
Hotels design rooms AROUND their HVAC airflow. Homeowners rarely do this.
This positioning alone can improve comfort by 20–30%.
🧠 🔟 Tony’s Hotel Sizing Secrets Every Homeowner Should Steal
Here’s my personal cheat-sheet based on years of working with hotels:
✔️ Secret #1: Size for the worst 5% of weather.
That’s when comfort fails.
✔️ Secret #2: Sun exposure beats square footage.
A sunny 250 sq ft room can need more BTUs than a shaded 350 sq ft room.
✔️ Secret #3: Humidity is half the cooling load.
Moisture removal is more important than most homeowners realize.
✔️ Secret #4: Corner rooms act like bigger rooms.
Two exterior walls = more heat exchange.
✔️ Secret #5: Windows dominate heating and cooling.
One big window can change the entire sizing calculation.
✔️ Secret #6: Heat kits matter more than BTUs in winter.
Do NOT underestimate heating wattage.
✔️ Secret #7: People load must be included.
Your family (or guests) add heat. So do laptops, TVs, and lighting.
✔️ Secret #8: Real room usage matters more than charts.
Work-from-home? Sleep hot? Cook a lot? It all impacts load.
✔️ Secret #9: Airflow direction is as important as BTUs.
Hotels always optimize placement. Homeowners can too.
✔️ Secret #10: Consistency is king.
Hotels size for long, steady cycles — not short blasts of cold air.
When you apply these secrets at home, your PTAC performs like a hotel-grade comfort system.
🏁 11️⃣ Tony’s Final Take: Comfort Isn’t Luck — It’s Calculation
Here’s the truth:
🔥 Hotels don’t get comfort right by accident.
🔥 They get it right because they size systems smarter than anyone.
🔥 And homeowners can absolutely use those same strategies.
When you size your PTAC for:
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sun exposure
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humidity
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room layout
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occupancy
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insulation
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heat load
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real-world usage
…you stop fighting your HVAC system and start enjoying it.
Your home becomes more comfortable, your energy bills stay in check, and your system lasts longer.
Hotels don’t get second chances — and that’s why their sizing methods are worth borrowing.
Use their tricks, think like they do, and you’ll never suffer through an underperforming room again.
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In the next topic we will know more about: Future-Proof Sizing: Choosing a PTAC That Grows with Your Remodel Plans
