EGC vs GEC — the difference in a solar system

Two grounding conductors, two different jobs, two different sizing tables — and a lot of plan sets that mix them up. The EGC and the GEC both have "grounding" in the name, but one clears faults between equipment and the other ties the whole system to the earth. Knowing which is which keeps your one-line clean and your inspection short.

The one-sentence distinction

• EGC — equipment grounding conductor: bonds metal parts to each other and back to the source so a fault has a low-impedance path and the breaker trips. It is the array-frame and enclosure safety path.
• GEC — grounding electrode conductor: connects the system to the earth — the ground rod, Ufer, or other electrode. It stabilizes voltage to ground and handles lightning/surge energy to earth.

How the EGC is sized: 250.122

The EGC is sized off the overcurrent device protecting the circuit, using Table 250.122. Bump up the OCPD and the minimum EGC grows with it. On the PV side, module frames and racking are bonded and carried back through EGCs sized to the circuit's protection. Note the special rule for PV: where there is no overcurrent device in a small source circuit, the EGC can be sized to the circuit conductors instead. See EGC sizing under 250.122.

How the GEC is sized: 250.66

The GEC is sized from the system/service conductors using Table 250.66, with practical caps depending on the electrode type — for example, the connection to a ground rod need not exceed 6 AWG copper, and to a concrete-encased electrode 4 AWG copper. See GEC sizing under 250.66.

Where each lands in a PV install

• On the roof: module frames and rails are bonded with listed hardware; the bonding path is continued by the EGC back toward the equipment.
• At the inverter and disconnects: enclosures are bonded via EGCs.
• At the service / grounding point: the GEC ties the grounding system to the electrode (rod, Ufer, water pipe where permitted).

The underlying purpose of all of it is one idea: bonding to create a fault path, grounding to reference the system to earth. Grounding details drawn wrong are a classic correction — see why solar permits get rejected.

A memory hook that sticks

Two E's and two G's. EGC connects Equipment; GEC connects to the Ground (earth) electrode. Or by table: 122 is for equipment (250.122), 66 is for the electrode (250.66). Once the pairing is automatic you'll stop reaching for the wrong table.

There's one more distinction worth holding onto. The EGC can run in many places — every enclosure, every rail, every module frame is in the equipment-grounding path. The GEC is usually a single conductor from the grounding point to the electrode. If your one-line shows a web of grounding conductors, those are EGCs; the one lead heading to the ground rod or Ufer is the GEC.

The mistake reviewers catch

Labeling a single conductor as doing both jobs, or sizing the array grounding conductor from the wrong table. The EGC follows 250.122 (device), the GEC follows 250.66 (system) — never swap the tables. Another common slip is oversizing the GEC needlessly: the connection to a ground rod need not exceed 6 AWG copper no matter how large the service, because the earth simply can't carry more.

Grounding rules and PV-specific allowances vary across NEC editions and inverter topologies. Confirm the enforced code and local amendments with your AHJ, and have a licensed electrician or PE review, sign and stamp the design before filing or energizing.

Educational reference, reviewed 2026-07. A design aid, not a substitute for a licensed electrician or PE. Confirm the enforced NEC edition and local amendments with your AHJ.