
Electrical Load Calculation & Equipment Sizing Assistant
Automate electrical load calculations with NEC compliance verification
What You Can Do
This skill automates the detailed calculations required for electrical system design, converting connected loads to demand loads, sizing conductors and equipment per NEC standards, and analyzing voltage drop across feeders and branch circuits. You input project parameters and receive complete load schedules, equipment recommendations with ampacity ratings, conductor specifications, and code citations—eliminating manual calculation errors and enabling faster design iterations for permit-ready documentation.
Features
Applies diversity and demand factors for residential, commercial, and mixed-use occupancies per NEC Article 220
Calculates wire gauges, ampacities, and protection device ratings per NEC Article 310 for feeders and branch circuits
Sizes service equipment, panelboards, transformers, and distribution gear with load analysis
Computes voltage drop across conductors and recommends conductor upgrades to maintain code-compliant performance
Cross-references calculations against current NEC articles with applicable local amendments
Produces organized equipment and demand schedules ready for drawings and specifications
Evaluates alternative designs (conductor types, equipment options) for cost and efficiency trade-offs
Includes NEC article references for AHJ review and permit submission
Example Output
Example 1: Residential Service Calculation
Input: 3-bedroom single-family home, all-electric
Output:
- Connected Load: 42.5 kW → Demand Load: 28.3 kW (per NEC 220.82)
- Service Size: 150A minimum
- Main Disconnect: 150A OCPD
- Conductor: 1/0 AWG Cu (THHN) for 150A service
- Voltage Drop: 2.1% at 200 ft from meter to panel ✓ Compliant
Example 2: Commercial Office Building Feeder
Input: 4-floor office, 40,000 sq ft, 20A general lighting circuits + dedicated HVAC feeder
Output:
- Lighting Demand: 48 kW (25% demand factor)
- HVAC Load: 65 kW (diversity applied)
- Total Feeder Demand: 103.5 kA
- Feeder Conductor: 4x 2/0 AWG Cu THHN parallel in 2" PVC
- Main Breaker: 400A, Series Rated with panelboard
- Voltage Drop: 1.8% at 350 ft ✓ Compliant (NEC 215.2)
- NEC Citation: 220.40, 310.15(B)(3)(a), 215.4(D)
What's Included
- SKILL.md: Complete skill definition with capabilities, use cases, and scope boundaries
- Load Calculation Template: Structured worksheet for capturing project inputs (building type, occupancy, square footage, appliance schedules)
- Demand Factor Reference Chart: NEC Table 220.42, 220.54, and 220.82 summary for quick factor lookup
- Equipment Sizing Checklist: Step-by-step verification for service sizing, feeder selection, and conductor ampacity confirmation
- Code Compliance Verification Worksheet: Cross-check calculations against NEC articles 215, 220, and 310 requirements
Who It's For
- MEP/Electrical Engineers — Design electrical systems with code-compliant calculations and reduced iteration cycles
- Electrical Designers — Create load schedules and equipment specifications for permit submission and construction documents
- Electrical Contractors — Verify design calculations and troubleshoot sizing issues on existing or retrofit projects
- Architects — Estimate electrical demand early in design for feasibility and budget planning
- Building Code Officials — Review load calculation methodology and verify NEC compliance for permit review
Best For
- Service equipment and main feeder sizing for new construction or upgrades
- Branch circuit and sub-feeder conductor selection for commercial/residential projects
- Demand load analysis for mixed-use occupancies or complex building types
- Voltage drop mitigation and conductor upsizing recommendations
- NEC compliance verification and code citation documentation for AHJ review
- Equipment schedule generation and specification development







