Load Calculator
What size HVAC system does this building need? A simplified estimate using industry rules of thumb — not a replacement for a full Manual J.
Enter the building square footage to estimate the system size needed.
What to do with this number
- This is a simplified estimate, not a Manual J. Use it for quick customer conversations and rough equipment sizing. It tells you the ballpark — 3.5 tons vs 5 tons — not the exact answer.
- Always run a proper Manual J before permitting. Florida building codes require a Manual J load calculation for new installations. This calculator does not replace that. Use it to set expectations, then do the formal calculation.
- Do not oversize. A system that is too large short-cycles, wastes energy, and fails to dehumidify in Florida's humid climate. A 5-ton system in a 3.5-ton house runs in short bursts and leaves the home clammy. Right-sizing matters more than oversizing.
- Adjust for real conditions. High ceilings, excessive windows, poor insulation, or a west-facing orientation all increase the load. The adjustments in this calculator account for the major factors, but unusual conditions may push it higher.
This is a simplified estimate using industry rules of thumb. For equipment selection, permit applications, and warranty compliance, a proper Manual J load calculation is required. Ask your contractor for a room-by-room load calculation before purchasing a system.
Sources (3)
- ACCA — simplified load estimation methodology
- ASHRAE — residential cooling/heating load guidelines
- DOE — climate zone classifications