Electrical Load Calculation

Calculate electrical panel sizes, feeder requirements, and apply demand factors per local codes.

Size panel for office building (North America):
• Floor area: 10,000 SF
• General lighting: 10 kW
• Receptacles: 15 kW
• HVAC: 40 kW (10-ton RTU, 208V 3-phase)
• Computer room: 5 kW
• Break room appliances: 3.7 kW
• Code: NEC 2020
• Voltage: 208V/120V 3-phase

LOAD SUMMARY WITH DEMAND FACTORS:
• Lighting: 10,000 W × 1.0 = 10,000 W
• Receptacles: 15,000 W × 0.6 (NEC 220.44) = 9,000 W
• HVAC: 40,000 W × 1.25 (NEC 430.24) = 50,000 W
• Computer room: 5,000 W × 1.0 = 5,000 W
• Appliances: 3,700 W × 0.75 = 2,775 W

TOTAL CALCULATED LOAD: 76,775 W

PANEL SIZING:
Current = 76,775 W / (208V × √3 × 0.85 PF) = 250 A
With 125% safety factor: 313 A

RECOMMENDATION: 400A Main Breaker Panel
Feeder: 500 kcmil THHN copper (3 conductors + ground)
Conduit: 3" EMT

✅ NEC 2020 COMPLIANT

Key Results

Common Use Cases

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