What Is Equipment Grounding Conductor? Definition & Guide

Key Takeaways

The equipment grounding conductor (EGC) provides the low-impedance fault current path that allows overcurrent devices to trip during a ground fault, protecting people from electric shock
NEC 250.122 governs EGC sizing based on the rating of the overcurrent protection device (OCPD) protecting the circuit — not on the ampacity of the circuit conductors
Solar panel grounding can be achieved through wire-type EGCs (copper or aluminum), listed racking systems (UL 2703), or qualifying metal conduit per NEC 250.118
UL 2703-listed racking systems can serve as the EGC for the array, eliminating a separate grounding wire when installed per manufacturer instructions
The EGC and the grounding electrode conductor (GEC) serve different functions — the EGC carries fault current to trip the breaker, while the GEC connects the system to earth
Undersized or discontinuous equipment grounding conductors in solar installations are a top cause of AHJ inspection failures across U.S. jurisdictions

What Is an Equipment Grounding Conductor?

An equipment grounding conductor (EGC) is a conductor that connects the non-current-carrying metal parts of electrical equipment — solar panel frames, racking rails, inverter housings, junction boxes, disconnects, and combiner boxes — back to the grounding bus at the main service panel. Its job is to carry fault current when a live conductor accidentally contacts an equipment enclosure or metal frame, creating a path with low enough impedance to trip the circuit’s overcurrent protection device quickly.

The EGC does not carry current during normal operation. It sits idle until a ground fault occurs. When it does, the EGC becomes the return path for fault current, allowing the breaker or fuse to detect the overcurrent condition and open the circuit within milliseconds.

In a properly grounded PV system, if a damaged conductor contacts a solar panel frame, fault current flows through the equipment grounding conductor back to the source — not through the installer, homeowner, or firefighter who touches the frame. The EGC is the single component that makes this possible.

For solar designers using solar design software, specifying the correct EGC type and size for every circuit in the array is a code requirement that directly affects permit approval. Getting it wrong means failed inspections and costly rework.

Types of Equipment Grounding Conductors in Solar PV

Most Common

Wire-Type EGC (Copper/Aluminum)

A dedicated insulated or bare conductor run alongside the circuit conductors. Copper is standard for residential solar; aluminum is permitted in larger commercial systems where cost savings justify the increased wire size. Green insulation or green with yellow stripe identifies the EGC. Sized per NEC 250.122 based on the OCPD rating protecting the circuit.

Array Level

Racking as EGC (UL 2703 Listed)

When a racking system is listed to UL 2703 as an equipment grounding conductor, the metallic racking structure itself serves as the EGC from module frames to a single termination point. This eliminates the need for a separate grounding wire across the array. The racking must be installed exactly per manufacturer specifications — every splice, clamp, and bonding point must use listed hardware.

Raceway

Conduit as EGC

Certain metal conduit types qualify as equipment grounding conductors under NEC 250.118. EMT (Electrical Metallic Tubing), RMC (Rigid Metal Conduit), and IMC (Intermediate Metal Conduit) can serve as the EGC when joints are made tight and the raceway is continuous. Many AHJs still require a separate wire-type EGC in addition to the conduit, so check local amendments.

Different Function

Grounding Electrode Conductor (GEC)

Often confused with the EGC, the GEC connects the grounding bus to the grounding electrode (ground rod, concrete-encased electrode, or ground ring). The GEC provides the earth connection; the EGC provides the fault current path. They terminate at the same grounding bus but serve separate purposes. The GEC is sized per NEC 250.66 based on the largest service entrance conductor.

EGC Comparison Table

EGC Type	NEC Reference	Sizing Method	Advantages
Copper Wire EGC	250.118(1), 250.122	Table 250.122 — based on OCPD rating	Universal acceptance by AHJs; best conductivity per cross-section; easy to inspect
Aluminum Wire EGC	250.118(1), 250.122	Table 250.122 — one size larger than copper equivalent	Lower material cost for long commercial runs; lighter weight
UL 2703 Racking	690.43(A), UL 2703	Manufacturer listing determines capacity	Eliminates separate array grounding wire; fewer labor hours; cleaner installation
EMT/RMC Conduit	250.118(2)-(5)	Conduit trade size inherently determines capacity	Dual function as raceway and EGC; no additional conductor needed
Grounding Electrode Conductor (GEC)	250.66	Table 250.66 — based on largest service conductor	Connects system to earth; provides voltage reference; dissipates lightning energy

EGC Sizing per NEC 250.122

EGC Sizing Rule — NEC 250.122

EGC minimum size = f(OCPD rating protecting the circuit)

The equipment grounding conductor is sized based on the rating of the overcurrent protection device (breaker or fuse) that protects the circuit — not on the ampacity of the circuit conductors and not on the system’s generating capacity. This is a common point of confusion. NEC Table 250.122 provides the minimum EGC sizes:

OCPD Rating (Amperes)	Minimum Copper EGC	Minimum Aluminum EGC
15	14 AWG	12 AWG
20	12 AWG	10 AWG
30	10 AWG	8 AWG
40	10 AWG	8 AWG
60	10 AWG	8 AWG
100	8 AWG	6 AWG
200	6 AWG	4 AWG
300	4 AWG	2 AWG
400	3 AWG	1 AWG

Practical example for residential solar: A typical string inverter circuit protected by a 20A breaker requires a minimum 12 AWG copper EGC. If the same circuit uses a 30A breaker, the minimum jumps to 10 AWG copper. Many installers default to 10 AWG copper for all residential PV circuits regardless of OCPD rating — this satisfies NEC 250.122 for circuits protected up to 60A and eliminates sizing confusion in the field.

For commercial systems: Larger arrays with 100A or 200A combiners require 8 AWG or 6 AWG copper EGCs respectively. When multiple circuits share a raceway, each circuit needs its own EGC unless a single EGC is sized for the largest OCPD in the raceway.

UL 2703 Racking as EGC — Know the Limits

A UL 2703-listed racking system can serve as the equipment grounding conductor for solar panel grounding across the array, but only under strict conditions. The racking must be installed per the manufacturer’s installation manual with all listed bonding hardware at every module and splice point. If a single splice is missing listed hardware, or if a non-listed clamp is substituted, the entire racking assembly loses its qualification as an EGC. A separate wire-type EGC is still required from the racking termination point to the grounding bus at the main panel. The UL 2703 listing only covers the array-level portion of the grounding path.

EGC vs. GEC: Understanding the Difference

These two conductors are frequently confused, but they serve fundamentally different purposes in a solar installation:

Equipment Grounding Conductor (EGC): Carries fault current from equipment enclosures back to the source so the OCPD can trip. It protects people. Sized per NEC 250.122 based on OCPD rating.
Grounding Electrode Conductor (GEC): Connects the grounding bus to the earth via a grounding electrode. It stabilizes voltage and dissipates transient energy (lightning, switching surges). Sized per NEC 250.66 based on the largest ungrounded service conductor.

Both conductors terminate at the main grounding bus, but they serve separate safety functions. A system can have a properly installed GEC and still be unsafe if the EGC path is broken — because fault current has no low-impedance return path to trip the breaker. Conversely, a system with a solid EGC but no GEC lacks a stable earth reference and lightning protection.

When designing systems in solar design software, both the EGC and GEC must be specified on the electrical line diagram and sized correctly for permit approval.

Practical Guidance

Equipment grounding conductor requirements affect design, installation, and how you communicate safety to customers. Here is role-specific guidance:

Size the EGC from the OCPD, not the wire. The most common design error is sizing the equipment grounding conductor based on circuit conductor ampacity instead of the overcurrent device rating. NEC 250.122 is clear: EGC size follows the OCPD rating. A 20A breaker means 12 AWG copper minimum, regardless of whether the circuit conductors are 10 AWG or 8 AWG.
Show the EGC on your electrical line diagrams. AHJs expect to see the equipment grounding conductor explicitly called out on single-line and three-line diagrams — size, type, and routing. Use solar design software that auto-generates these details to avoid omissions.
Specify whether racking qualifies as EGC. If the racking is UL 2703-listed for use as an EGC, note this on the plan set with the listing number. If it is not, include a wire-type EGC from every module frame to the grounding bus.
Account for conduit as EGC limitations. Even where EMT or RMC qualifies as an EGC per NEC 250.118, many jurisdictions require a supplemental wire-type EGC inside the conduit. Check local code amendments before relying on conduit alone.

Run the EGC with the circuit conductors. NEC 300.3(B) requires the EGC to be routed with the circuit conductors it protects — in the same raceway, cable, or trench. Separating them creates inductive impedance that can prevent the OCPD from tripping during a fault.
Verify continuity from the farthest module to the ground bus. Before calling for inspection, test the equipment grounding path with a low-resistance ohmmeter. Resistance should be well under 1 ohm from any module frame to the main grounding bus. High readings indicate a loose connection or break in the path.
Use listed lugs and connectors. Every EGC termination must use a connector listed for the purpose per NEC 250.8. Wire nuts are not acceptable for grounding connections in many jurisdictions. Lay-in lugs, compression connectors, and listed grounding clamps are the standard.
Do not reduce EGC size for long runs. Unlike circuit conductors, the EGC does not get upsized for voltage drop. However, NEC 250.122(B) requires the EGC to be increased when ungrounded conductors are increased in size for voltage drop. If you upsize home run conductors from 10 AWG to 8 AWG, the EGC must be proportionally increased.

Explain grounding in plain terms. Homeowners want to know their system is safe. Tell them that every metal component in the solar array is connected by a dedicated grounding wire back to the electrical panel. If anything goes wrong, the breaker trips instantly. That is what the equipment grounding conductor does.
Use code compliance as a differentiator. Many homeowners receive quotes from installers who cut corners on grounding. Emphasize that your designs include properly sized equipment grounding conductors per NEC requirements and that the local inspector verifies every connection.
Address the safety question directly. When a homeowner asks “is solar safe on my roof?”, the answer starts with grounding. Solar panel grounding ensures that fault current flows through the wiring, not through people. Every metal part is connected to a dedicated safety conductor that trips the breaker if a fault occurs.
Mention the inspection process. Let customers know that grounding is one of the first things the electrical inspector checks. Pass the inspection on the first visit, and the system gets energized faster — which means savings start sooner.

Design Code-Compliant Grounding Systems Automatically

SurgePV auto-sizes equipment grounding conductors per NEC 250.122, generates electrical line diagrams with EGC callouts, and produces permit-ready plan sets — all from a single design.

Book a Demo

No commitment required · 20 minutes · Live project walkthrough

Sources and References

NEC Article 250 — Grounding and Bonding. Covers equipment grounding conductor requirements (250.118, 250.122), effective ground fault current paths (250.4), and grounding electrode conductor sizing (250.66).
NEC Section 690.43 — Equipment Grounding and Bonding for PV systems. Requires all exposed non-current-carrying metal parts of modules, mounting systems, and other equipment to be grounded per Article 250.
UL 2703 — Standard for Mounting Systems, Mounting Devices, Clamping/Retention Devices, and Ground Lugs for Use with Flat-Plate Photovoltaic Modules and Panels. Establishes the listing criteria for racking systems that qualify as equipment grounding conductors.

Frequently Asked Questions

What is an equipment grounding conductor in a solar installation?

An equipment grounding conductor (EGC) in a solar installation is a conductor that connects all non-current-carrying metal parts — panel frames, racking, inverter enclosures, junction boxes, and disconnects — to the grounding bus at the main electrical panel. It provides a low-impedance path for fault current so that the circuit breaker or fuse trips quickly if a live conductor contacts metal equipment. The EGC is sized per NEC 250.122 based on the overcurrent protection device rating, not the circuit conductor size. Solar panel grounding through a properly sized EGC is required by NEC 690.43 for every PV system.

Can solar panel racking serve as the equipment grounding conductor?

Yes, but only when the racking system is UL 2703-listed specifically for use as an equipment grounding conductor and installed exactly per the manufacturer’s instructions. Every module clamp, rail splice, and bonding point must use the listed hardware specified in the installation manual. If any non-listed component is substituted or a connection is missed, the racking loses its EGC qualification, and a separate wire-type equipment grounding conductor must be installed. Even with UL 2703-listed racking serving as the array-level EGC, a wire-type EGC is still required from the racking termination point to the main grounding bus.

How do you size the EGC for a solar PV system?

EGC sizing for a solar PV system follows NEC Table 250.122. Find the ampere rating of the overcurrent protection device (breaker or fuse) protecting the circuit, then look up the minimum conductor size. For a 20A breaker, the minimum is 12 AWG copper or 10 AWG aluminum. For a 60A breaker, the minimum is 10 AWG copper or 8 AWG aluminum. If circuit conductors are increased in size for voltage drop per NEC 250.122(B), the EGC must be proportionally increased as well. Many residential solar installers standardize on 10 AWG copper for all PV circuits, which covers OCPD ratings up to 60A.