Electrical Panel Sizing Guide for Estimators

Proper electrical panel sizing is fundamental to accurate estimating. Undersized panels lead to change orders; oversized panels waste money. Here's what estimators need to know about panel sizing.

Load Calculation Basics

Panel sizing starts with a load calculation per NEC Article 220. Sum up all connected loads, apply demand factors, and size the panel and its feeder accordingly.

Key Considerations

• Spare Capacity — Most specs require 20-25% spare circuit capacity
• Future Growth — Design for future load additions where specified
• Voltage — 120/208V, 277/480V, or both? Determines panel type and pricing
• Main Breaker — Main breaker vs. main lug only affects panel cost
• Enclosure Type — NEMA 1 (indoor), NEMA 3R (outdoor), NEMA 4X (corrosive)

Panel sizing affects multiple cost elements including the panel, feeder, and upstream distribution. Our estimators verify panel sizing on every project. Request an estimate.