Grounding Electrode Conductor (GEC) Sizing Calculator (NEC 250.66)
Main electrical service entrance installations and service upgrades. Sizes grounding electrode conductor connecting the main electrical panel to ground rods, Ufer ground (concrete-encased), or metal water pipe.
Step-by-Step Derivation ▼ Show Steps
Calculations adhere to standard electrical engineering physics and National Electrical Code (NFPA 70) regulations.
Engineering Principles & Calculations
This calculator uses the exact mathematical relationships between Service Entrance Conductor Size (AWG/kcmil), Conductor Material (Copper / Aluminum), Grounding Electrode Type to determine Required GEC Wire Size (Copper AWG / Aluminum AWG). In practical installations, factors such as ambient raceway temperature, harmonic distortion, duty cycle continuous operation, and conductor impedance must be accounted for by a certified electrician.
Sizes grounding electrode conductor connecting the main electrical panel to ground rods, Ufer ground (concrete-encased), or metal water pipe.
Typical Application & Industry Guidelines
Main electrical service entrance installations and service upgrades.
Grounding Electrode Conductor (GEC) Sizing Calculator (NEC 250.66) Benchmark Lookup Table
| Service Conductor Size (Copper) | Service Conductor Size (Aluminum) | GEC Copper Wire Size | GEC Aluminum Wire Size |
|---|---|---|---|
| #2 AWG or smaller | 1/0 AWG or smaller | #8 AWG Copper | #6 AWG Aluminum |
| #1 AWG or 1/0 AWG | 2/0 AWG or 3/0 AWG | #6 AWG Copper | #4 AWG Aluminum |
| 2/0 AWG or 3/0 AWG (Standard 200A) | 4/0 AWG or 250 kcmil | #4 AWG Copper | #2 AWG Aluminum |
| Over 3/0 through 350 kcmil | Over 250 through 500 kcmil | #2 AWG Copper | 1/0 AWG Aluminum |
| Over 350 through 600 kcmil | Over 500 through 900 kcmil | 1/0 AWG Copper | 3/0 AWG Aluminum |
| Over 600 through 1100 kcmil | Over 900 through 1750 kcmil | 2/0 AWG Copper | 4/0 AWG Aluminum |