NEC 220.82 Optional Method1,000 Sq Ft • Fabrication / Automotive Shop with EV ChargerMarginal Capacity
100 Amp Heavy-Duty Shop Subpanel Load Calculation
Complete electrical demand load breakdown following NEC Article 220.82. Formally verified for electrical permit submissions, service disconnect sizing, and utility service drop requirements.
Calculated Demand115 Amps@ 240V Single Phase
Recommended Panel125 AmpsNEC Standard Rating
Service Feeder (Al)1/0 AWGTable 310.12 (75°C)
Minimum Conduit1-1/2"EMT / PVC Sch 40
Connected Appliance Profile & Nameplate Loads
Specific mechanical equipment ratings evaluated for this residential dwelling unit
Cooking EquipmentNone (0 VA)
Clothes DryerNone (0 VA)
Water HeatingPoint-of-Use 2.5 Gal Electric (1,500 VA)
HVAC Primary Heating/Cooling2-Ton Mini-Split Heat Pump (3,200 VA)
Electric Vehicle Supply (EVSE)32A Level 2 EVSE (7,680 VA)
Auxiliary Fixed Appliances240V MIG/TIG Welder 50A (12,000 VA), 5HP Air Compressor 240V (5,500 VA), Shop Tools & Dust Collector (4,800 VA)
NEC 220.82 Step-by-Step Demand Worksheet
Official calculation table matching municipal electrical permit application format
| Calculation Step • NEC Section | Connected VA | Demand Factor | Demand VA |
|---|---|---|---|
| General Lighting & Receptacles3 VA/sq ft • NEC 220.82(B)(1) | 3,000 VA | Subtotal Group | — |
| Small Appliance Circuits2 Circuits @ 1,500 VA • NEC 220.82(B)(2) | 0 VA | Subtotal Group | — |
| Laundry Branch Circuit1 Circuit @ 1,500 VA • NEC 220.82(B)(2) | 0 VA | Subtotal Group | — |
| Fixed & Fastened-in-Place AppliancesRange, Dryer, WH, DW, Disposal • 220.82(B)(3) | 23,800 VA | Subtotal Group | — |
| General Connected Load Subtotal | 26,800 VA | — | — |
| • First 10,000 VA of General Load | 10,000 VA | 100% | 10,000 VA |
| • Remainder above 10,000 VA | 16,800 VA | 40% | 6,720 VA |
| General Demand Load Subtotal | — | 220.82(B) | 16,720 VA |
| Heating & Air Conditioning (HVAC)Largest Non-Coincident Load • NEC 220.82(C) | 3,200 VA | 100% | 3,200 VA |
| Electric Vehicle Charger (EVSE)Continuous Load • NEC 625.42 | 7,680 VA | 100% / 125% | 7,680 VA |
| TOTAL CALCULATED DEMAND LOAD | — | Total / 240V | 27,600 VA • 115 A |
Service Conductor & Grounding Sizing Schedules
Minimum wire gauges and raceway sizes compliant with NEC Table 310.12 and Table 250.66
Service Entrance Conductors
Copper Conductor (THHN/XHHW):#1 AWG Copper THHN (130A) or #2 Cu for 100A
Aluminum Conductor (XHHW-2):1/0 AWG Aluminum XHHW-2
Minimum Raceway / Conduit:1-1/2" PVC Sch 40 Underground
Temperature Rating:75°C Terminations
Grounding & Bonding Electrode System
GEC to Water Pipe / Intersystem:#6 AWG Bare Copper
Ground Rod System:Dual 5/8" × 8ft Rods (6ft Spaced)
GEC to Ground Rods (Max):#6 AWG Copper
Main Bonding Jumper:Installed at Main Disconnect Only
Master Electrician Inspection & Installation Notes
- Calculated demand is 115.0A when combining a 32A EV charger with a 50A welder and 5HP compressor.
- A 100A subpanel is marginal; a 125A subpanel fed with #1 AWG copper or 1/0 aluminum is recommended for fabrication shops.
- Underground installation tip: Bury Schedule 40 PVC conduit at least 18 inches deep per NEC Table 300.5.
Frequently Asked Code Questions
What wire size do I need for a 100 amp subpanel 100 feet away?
For a 100 ft run at 100A, use #1 AWG copper or 1/0 AWG aluminum to limit voltage drop to under 2% per NEC Table 310.16.
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