Overview
The commercial load calculator handles the more complex demand factor calculations required for non-dwelling occupancies. Commercial buildings use occupancy-specific lighting demand factors (Table 220.42/120.42), receptacle demand factors, and motor load calculations that don’t apply to residential work.
The calculator supports multiple occupancy types: office, retail, restaurant, warehouse, hospital, hotel/motel, and multi-family dwelling.
Key Differences from Residential
Commercial load calculations differ from residential in several important ways:
- Lighting loads use occupancy-specific VA/sq ft values and demand factor tables instead of the flat residential rate
- Receptacle loads are calculated per outlet (180 VA each) or per foot of multi-outlet assembly
- Motor loads require 125% of the largest motor plus 100% of all others (NEC 430.24)
- Kitchen equipment has its own demand factor table (Table 220.56/120.56)
- No optional method — commercial calculations use the standard method with individual demand factor tables
- Three-phase service is common, requiring balanced phase loading
Inputs
- Occupancy type: Office, retail, restaurant, warehouse, hospital, hotel/motel, etc.
- Square footage: Total building area for lighting load calculation
- Receptacle count: Number of general-purpose receptacle outlets
- Motor loads: HP rating, voltage, phase, and duty type for each motor
- Kitchen equipment: Number and rating of commercial kitchen appliances
- HVAC loads: Heating and cooling equipment ratings
- Special loads: Signs (NEC 600.5), elevators, fire pumps, etc.
NEC References
- NEC 220.40–44/120.40–44 — general requirements and demand factors
- NEC Table 220.42/120.42 — lighting demand factors by occupancy
- NEC Table 220.56/120.56 — kitchen equipment demand factors
- NEC 430.24 — motor load calculation (125% largest + 100% others)
- NEC 430.52 — motor branch circuit OCPD sizing
Try it yourself
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