Why Sizing Matters
When it comes to heating and cooling with a PTAC unit, size isn’t just about space—it’s about efficiency. A unit that’s too small will run constantly and never catch up. One that’s too large? It’ll short-cycle, waste energy, and leave you with muggy air.
Here’s how to size it right the first time.
Start With the Basics: BTU per Square Foot
In HVAC, we use BTUs (British Thermal Units) to measure how much cooling or heating a unit can handle. The general rule of thumb is:
-
20 BTUs per square foot for standard rooms
But other factors—like ceiling height, sunlight, insulation, and heat-generating equipment—also come into play.
🔗 U.S. Department of Energy – BTU Calculator Basics
PTAC Sizing Chart (Quick Reference)
| Room Size (sq ft) | Recommended PTAC Size (BTU) |
|---|---|
| 300–400 | 7,000 – 9,000 BTU |
| 400–500 | 9,000 – 12,000 BTU |
| 500–600 | 12,000 – 14,000 BTU |
| 600–700 | 14,000 – 15,000 BTU |
| 700–800 | 15,000 – 17,000 BTU |
That puts the 14,700 BTU Amana PTAC right in the sweet spot for rooms around 600–750 sq ft—think studio apartments, hotel rooms, or small offices.
Special Considerations
🌞 Southern Exposure or Direct Sunlight
Add 10% more BTUs if the room gets strong afternoon sun.
👨👩👧👦 High Occupancy
More people = more body heat. Add 600 BTUs per additional person beyond two.
🍳 Kitchen Areas
Add 4,000 BTUs if the room has a stove, oven, or other heat-generating appliances.
🔗 ASHRAE Guidelines – HVAC Load Calculations
What About the Electric Heat?
The Amana unit on our pillar page comes with a 3.5 kW electric heater. That’s equivalent to roughly 11,900 BTUs of heat, making it suitable for mild to moderate winters in most of the U.S.
Mike’s Tip: If you’re in the upper Midwest or Northeast, you might want a unit with a 5 kW or supplemental baseboard heat during deep freezes.
Mistakes to Avoid
❌ Don’t go too big. You’ll get temperature swings, poor humidity control, and higher power bills.
❌ Don’t assume square footage is everything. Ceiling height, insulation, and windows all play a role.
❌ Don’t forget voltage. Make sure the unit matches your property’s electrical service—120V vs 230V matters!
Final Tips From Mike
Sizing your PTAC isn’t guesswork—it’s a mix of square footage, room conditions, and what you’re trying to accomplish. If you’re cooling a 600–700 sq ft room with standard insulation and typical occupancy, the 14,700 BTU Amana PTAC is just about perfect.
Need help dialing it in for your specific space? Don’t be afraid to reach out to a pro—or call up The Furnace Outlet’s support crew. They’ll walk you through the specs, no pressure.
In the next topic you will read: What Is a PTAC Unit and How Does It Work?
