Loading Calculator...
Please wait a moment
Please wait a moment
Calculate the correct size for your heating and cooling system. Get accurate sizing for air conditioners, furnaces, and heat pumps based on your home's characteristics.
Did you find this calculator helpful?
HVAC sizing is the process of determining the correct capacity for heating, ventilation, and air conditioning equipment. Proper sizing is critical for comfort, efficiency, and equipment longevity.
Manual J is the industry standard for calculating heating and cooling loads. Developed by ACCA (Air Conditioning Contractors of America), it considers:
Pro Tip: Always request a Manual J calculation from your HVAC contractor. This $100-200 investment ensures proper sizing and can save thousands in energy costs over the life of the equipment.
The U.S. Department of Energy divides the country into climate zones based on heating and cooling degree days:
| Zone | Climate | Example Cities | Primary Need |
|---|---|---|---|
| 1 | Very Hot-Humid | Miami, Key West | Cooling dominant |
| 2 | Hot | Houston, Phoenix, Las Vegas | Cooling dominant |
| 3 | Warm | Atlanta, Dallas, Los Angeles | Mixed |
| 4 | Mixed | Washington DC, St. Louis | Mixed |
| 5 | Cool | Chicago, Denver, NYC | Heating dominant |
| 6 | Cold | Minneapolis, Boston | Heating dominant |
| 7 | Very Cold | Duluth, Anchorage | Heating dominant |
Rough estimates for cooling capacity by home size (Zone 4, average conditions):
| Home Size (sq ft) | AC Size (Tons) | Cooling BTU | Heating BTU |
|---|---|---|---|
| 600-900 | 1.5 | 18,000 | 30,000 |
| 900-1,200 | 2.0 | 24,000 | 40,000 |
| 1,200-1,500 | 2.5 | 30,000 | 50,000 |
| 1,500-1,800 | 3.0 | 36,000 | 60,000 |
| 1,800-2,100 | 3.5 | 42,000 | 70,000 |
| 2,100-2,400 | 4.0 | 48,000 | 80,000 |
| 2,400-3,000 | 5.0 | 60,000 | 100,000 |
Split system with outdoor condenser and indoor evaporator coil. Cools entire home through ductwork.
Provides both heating and cooling. More efficient than resistance heat. Works well in zones 1-5.
Burns natural gas or propane for heat. Best for cold climates. Often paired with central AC.
Individual zone control without ductwork. Great for additions, older homes, or supplemental heating/cooling.
| Rating | Applies To | Minimum | Excellent |
|---|---|---|---|
| SEER2 | Air Conditioners | 13.4-14.3 | 20+ |
| HSPF2 | Heat Pump (Heating) | 7.5 | 10+ |
| AFUE | Furnaces | 80% | 95%+ |
| EER2 | AC (at peak load) | 10 | 14+ |
The general rule is 1 ton per 400-600 sq ft, but this varies by climate, insulation, and other factors. Hot climates may need 1 ton per 400 sq ft, while well-insulated homes in mild climates may need 1 ton per 600 sq ft.
Size for the larger load. In hot climates (zones 1-3), cooling typically dominates. In cold climates (zones 5-7), heating dominates. Mixed climates need both calculations.
No. Oversized systems cost more upfront, short cycle (turn on and off frequently), don't dehumidify properly, and wear out faster. Proper sizing is essential for comfort and efficiency.
Air conditioners typically last 15-20 years, heat pumps 10-15 years, and furnaces 15-25 years. Regular maintenance extends equipment life.
Heat pumps are more efficient in mild-to-moderate climates (zones 1-5). In very cold climates (zones 6-7), a gas furnace or dual-fuel system may be more practical and economical.