👋 Let’s Size That Room (the Right Way)
Hey folks—Mike Sanders here. If you’re shopping for a new PTAC unit and wondering, “What size do I need for my room?”, you’re not alone. It’s one of the most common questions I get, and it's also where a lot of people go wrong.
Buy a PTAC that’s too small and you’ll never get cool. Buy one too big and you’ll deal with short-cycling, wasted energy, and humidity issues. 💸💧
So today, we’re diving into how to properly size an R-32 PTAC unit to your space. Whether it’s for your home office, hotel room, or studio apartment, I’ll walk you through how many BTUs you need, what variables matter most, and why R-32 units are a smart upgrade for any room.
Let’s break it down.
🧮 PTAC Sizing Basics: What Are BTUs and Why Should You Care?
First things first: BTU stands for British Thermal Unit, and it measures how much heat an air conditioner can remove from a room per hour. The higher the BTU rating, the more powerful the unit.
Now, you might be tempted to just grab the biggest unit available, but that’s not how PTACs work best. If your unit is oversized, it’ll cool the room too fast without dehumidifying it, leaving you cold and clammy. If it’s too small, it’ll run constantly and wear out sooner.
As a rule of thumb:
| Room Size (sq ft) | Recommended BTUs |
|---|---|
| 150–250 | 7,000–9,000 |
| 250–350 | 9,000–10,000 |
| 350–450 | 10,000–12,000 |
| 450–550 | 12,000–14,000 |
| 550–700 | 14,000–15,000+ |
⚠️ These are starting points. Keep reading because room use, climate, insulation, and ceiling height all matter too.
For a professional reference, check out ENERGY STAR’s BTU room size chart for more accuracy.
🌡️ Adjusting for Real-World Factors
🏜️ 1. Climate Zone
Live somewhere hot like Phoenix or humid like Miami? Bump up your BTU range by 10–15%. If you’re in a cooler, dry zone like Denver, you can stay on the lower end.
The U.S. Department of Energy Climate Zone Map is a great tool if you're not sure where your region lands.
🧱 2. Room Insulation & Construction
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New builds with double-pane windows and spray foam insulation retain temps better, so you might not need as many BTUs.
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Older buildings with drafty windows or poor insulation? Add 1,000–2,000 BTUs to compensate.
🪟 3. Sunlight Exposure
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Rooms with large south-facing windows or sunrooms get hotter.
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If your space gets baked by sunlight all afternoon, you’ll need to increase BTU output by 10%.
🛌 4. Room Purpose
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Kitchens need more BTUs due to appliance heat—add at least 4,000 extra.
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Bedrooms can run lower, but I still like to size slightly higher so you don’t sweat through summer nights. 💤
👧 5. Number of Occupants
If more than two people regularly use the room, add 600 BTUs per person. Human bodies put out heat, whether we want them to or not!
⚙️ R-32 PTACs: Why Sizing Matters Even More Now
The newer R-32 PTAC units are more energy-efficient, have better heat exchange properties, and run at slightly different pressures than R-410A units. That means proper sizing is even more critical, because R-32 delivers better cooling—but only when matched correctly to your space.
According to Daikin Global, R-32 offers higher volumetric capacity, meaning systems can use less refrigerant to achieve the same (or better) performance. So don’t size up just because you’re used to older refrigerants.
🛍️ Real-World R-32 PTAC Sizing Examples
Here’s how I’d match units to room types:
🏠 Studio Apartment (350 sq ft, Chicago, new windows)
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Target BTUs: 10,000–11,000
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Recommended: 10K R-32 PTAC w/ heat pump
🏨 Hotel Room (300 sq ft, Las Vegas, west-facing windows)
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Target BTUs: 12,000–13,000
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Recommended: 12K R-32 PTAC with electric heat
💼 Home Office (250 sq ft, Atlanta, two people)
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Target BTUs: 9,000–10,000
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Recommended: 9K R-32 PTAC with low-decibel fan motor
Need help deciding? Always check energy input ratings (EER) and voltage too—especially if you're working with a 265V or 208/230V building. Check out this HVAC voltage guide for more help.
❌ Don’t Fall for These Sizing Myths
❗ “Bigger is always better.”
Nope. Oversized units short cycle, wear out faster, and don’t dehumidify well.
❗ “All PTACs are the same.”
Not true. R-32 PTACs are built differently. Check blower speeds, dehumidification settings, and heating type.
❗ “I’ll just match the old one.”
Dangerous move. That old PTAC might’ve been wrong to begin with—or the insulation/windows could’ve changed since then.
🧠 Mike’s Pro Tips for First-Time PTAC Buyers
✔️ Always check voltage and plug type before buying. A 230V unit won’t work in a 265V socket.
✔️ Choose heat pump models if you want efficiency year-round (vs. electric heat models which cost more to run).
✔️ Don’t forget the wall sleeve and grille—many units don’t come with them.
✔️ Buy from a supplier that understands HVAC—not just a box store. A good supplier helps with compatibility and shipping damage, like the folks at The Furnace Outlet.
🏁 Final Word from Mike
Getting the right size R-32 PTAC unit isn’t rocket science—it just takes a little planning. Take the time to measure your space, account for how you use it, and don’t fall for sizing myths. When in doubt, ask a pro or check with your supplier. The right fit means better comfort, lower bills, and longer-lasting equipment.
Need help troubleshooting your PTAC unit? Check out this guide for R-32 systems!
And if you're ready to browse R-32 PTACs that are efficient, affordable, and future-proof, head over to The Furnace Outlet’s R-32 PTAC collection and find your match. 🔧
Until next time—stay cool, stay smart.
— Mike
