Hey, it’s Jake 👋
When it comes to buying a PTAC heat pump, size matters—a lot more than most people think. Whether you’re installing one in a hotel room, a condo, or even a home office, getting the BTU sizing right can make or break your comfort level and energy savings.
I've helped a lot of folks avoid expensive mistakes, and today I’m going to help you do the same. So grab a notepad—or just bookmark this page—and let’s dive into how to choose the right size PTAC heat pump for your space.
Why PTAC Sizing Is So Important
Let me start with this: if your unit is too small, it’ll work overtime, run constantly, and still leave you sweating (or shivering). If it’s too big, you’ll get short cycles that skyrocket your bills and wear the unit out faster. Not to mention, oversized units don’t dehumidify properly.
The sweet spot? A right-sized unit that matches your room’s unique needs for both heating and cooling.
Step 1: Know Your Room Size 📏
The very first step is to figure out how big the room is. Here’s how to do it:
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Measure the length and width of the room in feet
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Multiply those numbers together
For example, a room that’s 20 feet long and 15 feet wide is:
20 ft × 15 ft = 300 sq. ft.That’s your baseline.
🛠️ Pro Tip: Ceiling height also plays a role—if it’s more than 8 feet, we’ll need to factor that in too.
Step 2: Match Room Size to BTU Range
Now that you’ve got your room size, use this rough BTU chart as a starting point:
| Room Size (sq ft) | Recommended BTU Range |
|---|---|
| 100–300 | 5,000 – 7,000 BTUs |
| 300–500 | 7,000 – 10,000 BTUs |
| 500–700 | 10,000 – 12,000 BTUs |
| 700–1,000 | 12,000 – 15,000 BTUs |
This gets you in the ballpark—but don’t go shopping just yet. There are still a few more critical factors that can increase or decrease your heating and cooling load.
Step 3: Factor in These 6 Things Before Finalizing Size
1. Sunlight Exposure
If your room gets a lot of direct sun during the day, bump your BTU rating up by 10% or more. Sun-facing windows can heat a space quickly, especially in the afternoon.
2. Insulation
If your room or suite is poorly insulated (think older buildings), you’ll lose more heat in the winter and gain more in the summer. That means your PTAC has to work harder. Increase the BTU capacity slightly in these cases.
3. Number of Windows and Doors
More windows = more heat exchange. If you’ve got sliding glass doors or oversized windows, factor in another 5–10% BTU increase.
4. Ceiling Height
A typical ceiling is 8 feet. If yours is higher (e.g., vaulted or cathedral ceilings), you’ve got more air volume to heat or cool. Add another 10% to your BTU requirement.
5. Room Purpose
Using the room as a gym, office with lots of electronics, or a kitchen? You’ll generate extra heat. In those cases, bump your BTU rating up a notch.
6. Number of People
If more than 2 people regularly occupy the room, add 600 BTUs for each additional person. People generate body heat—and it adds up.
Step 4: Use a BTU Calculator for Better Accuracy 🔍
If you’re ready to get more precise, try the BTU calculator from PickHVAC.com. It takes into account your:
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Room dimensions
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Insulation level
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Climate zone
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Sun exposure
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Number of occupants
It’s free, user-friendly, and will give you a more tailored recommendation than just a BTU chart.
Step 5: Choose the Right PTAC Heat Pump
Once you’ve got your target BTU rating, check out the available PTAC Heat Pumps at The Furnace Outlet. You’ll find models ranging from 7,000 to 15,000 BTUs, with features like digital controls, remote access, and Energy Star certifications.
💡 Here are a few top-selling sizes and where they shine:
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7,000–9,000 BTUs – Perfect for guest rooms, dorms, or studios up to 300 sq. ft.
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9,000–12,000 BTUs – Best for suites, larger hotel rooms, or small living areas.
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13,000–15,000 BTUs – Ideal for open-plan layouts, offices, or extended-stay units.
Be sure to choose a model with both heating and cooling BTU ratings listed—some units can heat more effectively than they cool (or vice versa).
Common PTAC Sizing Mistakes to Avoid 🚫
❌ Guessing Based on Similar Rooms
Just because your neighbor’s suite has a 12,000 BTU unit doesn’t mean you need one too. Every room is different.
❌ Ignoring Insulation and Windows
Don’t forget about heat loss and gain—it can make a huge difference in performance.
❌ Going Too Big “Just in Case”
Oversizing leads to short cycles, increased humidity, and higher wear on components. Trust the math.
PTAC Sizing FAQ with Jake
Q: What happens if I buy a PTAC that’s too small?
A: It’ll run nonstop, use more power, and never reach your desired temperature.
Q: Should I buy a PTAC based on heating or cooling BTUs?
A: Both matter. If you live in a cold climate, prioritize heating. If you're in Florida or Texas, focus more on cooling.
Q: Do all PTAC units have heat pumps?
A: No—some use electric resistance heat only. Make sure you’re selecting a heat pump model for year-round use.
Where to Learn More 🛠️
If you’re curious about optimizing HVAC in compact spaces, check out these great resources:
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ASHRAE’s Fundamentals Handbook: For detailed heating/cooling load calculations.
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Energy Saver HVAC Tips: U.S. DOE’s guidance on heating and cooling efficiency.
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Building Performance Institute (BPI): For whole-house performance and energy insights.
Final Thoughts from Jake ✅
Choosing the right size PTAC heat pump might seem intimidating, but it doesn’t have to be. With just a tape measure, a little math, and the right online tools, you can get it right the first time—and avoid wasted energy, uneven temps, and system breakdowns.
If you’re ever unsure, my advice is to measure carefully, adjust thoughtfully, and don’t overbuy. The right fit will make all the difference for your comfort and your wallet.
Catch you next time!
— Jake Lawson
