What Size Furnace for 1,500 Sq Ft?
Quick Answer: 60,000–80,000 BTU input (48,000–64,000 BTU output) in moderate climates. 70,000–90,000 BTU in cold climates (Zone 5-6). 45,000–60,000 BTU in warm climates.
Furnace BTU for 1,500 Sq Ft
| Climate Zone | BTU Input | BTU Output (80%) | Monthly Cost* |
|---|---|---|---|
| Zone 1 (Miami) | 45,000–60,000 | 36,000–48,000 | $55–75 |
| Zone 2 (Houston) | 50,000–65,000 | 40,000–52,000 | $60–80 |
| Zone 3 (Atlanta) | 60,000–80,000 | 48,000–64,000 | $70–100 |
| Zone 4 (NYC) | 65,000–85,000 | 52,000–68,000 | $80–110 |
| Zone 5 (Chicago) | 75,000–95,000 | 60,000–76,000 | $90–120 |
| Zone 6 (Minneapolis) | 80,000–100,000 | 64,000–80,000 | $100–130 |
*Estimated monthly heating cost at 80% AFUE, $1.20/therm natural gas, 2,000 heating hours/year.
Cost: 80% vs 95% AFUE Furnace
| Factor | 80% AFUE | 95% AFUE |
|---|---|---|
| Equipment Cost | $2,000–3,200 | $3,200–5,000 |
| Annual Heating Cost | $2,100 | $1,768 |
| 10-Year Total | $23,000–24,200 | $20,880–22,680 |
| Best For | Mild climates, budget | Cold climates, long-term |
Common Furnace Sizing Mistakes
- Using the old furnace size: Old units were often oversized. Modern homes need less heating due to better insulation
- Confusing input and output BTU: An 80,000 BTU input furnace at 80% AFUE only delivers 64,000 BTU output
- Skipping the load calculation: A Manual J is the only way to get exact sizing for your specific home
Frequently Asked Questions
What BTU furnace for 1,500 sq ft?
60,000–80,000 BTU input in moderate climates. 70,000–90,000 BTU in cold climates (Zone 5-6). 45,000–60,000 BTU in warm climates. Two-stage furnaces provide better comfort for this size.
Is an 80,000 BTU furnace enough for 1,500 sq ft?
Yes, in most climates. In Zone 6 (Minneapolis), 80,000-90,000 BTU may be needed for extreme cold. A high-efficiency (95%+ AFUE) 80,000 BTU furnace provides 76,000 BTU usable output.
What AFUE rating should I choose for 1,500 sq ft?
80% AFUE: lowest upfront cost. 92-95% AFUE: best balance for moderate climates. 96-98% AFUE: best for cold climates where the heating season is 5+ months. Federal tax credits available for 95%+ AFUE.
Disclaimer: Sizing estimates are preliminary. Final equipment selection should use ACCA Manual J load calculation by a licensed HVAC contractor.