When you’re planning to replace or upgrade your HVAC system, one of the most important questions is:
“What size system do I actually need?”
Choosing the right size — measured in tons for cooling and BTUs for heating — ensures your home stays comfortable, energy-efficient, and reliable throughout Texas’ hot summers and mild winters.
In this post, we’ll explain what those terms mean and how you can estimate your system size based on your home’s square footage.
📘 Quick Guide to Terms for HVAC Systems
What Is a “Ton” in HVAC?
A ton doesn’t mean weight — it’s a measure of cooling capacity.
1 ton of cooling = 12,000 BTUs per hour (the amount of heat the system can remove from your home in one hour).
Typical residential systems range from 1.5 to 5 tons.
What Is a BTU?
A BTU (British Thermal Unit) measures heat energy — both for cooling and heating.
- Cooling BTU shows how much heat the system can remove.
- Heating BTU shows how much heat the furnace or heat pump can deliver.
Why Size Matters
- An undersized system will run constantly and never fully cool or heat your home.
- An oversized system will short-cycle — turning on and off too quickly, wasting energy and wearing out faster.
The goal is to find the sweet spot where comfort meets efficiency.
📏 Approximate Cooling Capacity by Home Size (Texas Average)
| Home Size (Square Feet) | Estimated System Size | Approx. Cooling BTU Capacity |
|---|---|---|
| Up to 900 sq ft | 1.5 ton | ~18,000 BTU |
| 901–1,200 sq ft | 2 ton | ~24,000 BTU |
| 1,201–1,500 sq ft | 2.5 ton | ~30,000 BTU |
| 1,501–1,800 sq ft | 3 ton | ~36,000 BTU |
| 1,801–2,200 sq ft | 3.5 ton | ~42,000 BTU |
| 2,201–2,600 sq ft | 4 ton | ~48,000 BTU |
| 2,601–3,200 sq ft | 5 ton | ~60,000 BTU |
🏡 These are averages for the Central Texas climate (Austin area), assuming standard insulation and ceiling height.
🔥 Heating Capacity (BTU) Guidelines for Gas Furnaces
For gas furnaces, heating power is measured directly in BTUs of heat output.
Here’s a general rule of thumb for Texas homes:
| Home Size (Square Feet) | Approx. Furnace BTU Rating |
|---|---|
| Up to 900 sq ft | 40,000 BTU |
| 901–1,400 sq ft | 50,000–60,000 BTU |
| 1,401–1,800 sq ft | 70,000 BTU |
| 1,801–2,200 sq ft | 80,000 BTU |
| 2,201–2,600 sq ft | 90,000–100,000 BTU |
| 2,601–3,200 sq ft | 100,000–120,000 BTU |
💡 In Austin’s mild winters, you typically won’t need the highest furnace BTU rating.
For most homes, a 60,000–80,000 BTU gas furnace provides ample heating.
⚙️ Other Factors That Influence System Size
While square footage gives a good starting point, other factors matter too:
- Ceiling height: Taller ceilings require more capacity.
- Insulation quality: Better insulation can lower tonnage needs.
- Windows: Large or south-facing windows increase heat load.
- Number of occupants: More people = more body heat = higher cooling load.
- Duct system condition: Undersized or leaky ducts reduce actual performance.
A professional load calculation (Manual J) by an HVAC technician refines these estimates for your specific home.
💬 Final Thoughts
Your home’s ideal system size depends on more than square footage — but understanding tons and BTUs gives you a clear starting point.
For Central Texas homeowners, most systems fall between 2 and 5 tons of cooling and 60,000–100,000 BTUs of heating capacity.
Not sure what size fits your home?
Our Bree HVAC team can perform a detailed inspection and recommend the perfect match for comfort, efficiency, and budget.
Book your free system assessment today.
