HVAC Load Calculator
Calculate heating and cooling loads using Manual J methodology. Size your HVAC equipment correctly based on climate zone, insulation, and building characteristics.
7 Ton
Recommended A/C Size
82,336
Cooling BTU/hr
88,088
Heating BTU/hr
2800
CFM Required
Climate Zone Details
Zone
Mixed-Humid (DC)
Summer Design Temp
90°F
Winter Design Temp
15°F
Note: This is a simplified Manual J calculation. For permit applications, a full Manual J analysis by a licensed HVAC contractor is typically required. Oversizing can cause short-cycling and humidity issues.
Understanding Manual J Load Calculations
What is "Load"?
In HVAC terms, "load" refers to the amount of heat energy your system needs to remove (cooling load) or add (heating load) to maintain a comfortable temperature. It is measured in BTUs (British Thermal Units).
Why Size Matters
Proper sizing is critical for efficiency and comfort. "Bigger" is not better.
- Oversized Units: Cool too quickly and turn off before removing humidity. This leads to "short cycling," higher bills, and a clammy, uncomfortable home.
- Undersized Units: Run continuously on hot days and fail to reach the desired temperature, causing excessive wear on the compressor.
Factors This Calculator Considers
- Design Temperatures: Based on your Climate Zone (e.g., Miami vs Minneapolis).
- Insulation & Windows: R-values and window types (single vs double pane) drastically affect heat transfer.
- Occupancy: Humans generate heat (~400-600 BTUs/hr), which adds to the cooling load.