Grounding and bonding a PV system

Grounding and bonding are the quiet half of a safe PV system — the paths that carry fault current and keep metal from becoming energized. NEC Article 250 sets the general rules and Article 690 Part V adds the PV specifics. Here is what each conductor does and how it is sized.

Bonding vs grounding

The terms get used loosely, but they are different jobs:

• Bonding connects all the metal that shouldn't be energized — module frames, racking, enclosures — so they stay at the same potential and a fault has a low-impedance path back to the source.
• Grounding connects that bonded system to the earth through a grounding electrode (ground rod, Ufer, water pipe), stabilizing voltage and giving lightning and surges somewhere to go.

The equipment grounding conductor (EGC)

The EGC bonds each piece of equipment back toward the source. For PV circuits:

• Size it from NEC 250.122 using the circuit's overcurrent device rating.
• Example: a 20 A OCPD calls for a minimum 12 AWG copper EGC per the 250.122 table.
• 690.45 confirms the EGC follows 250.122 and need not be upsized for the PV 1.25 factors in most cases.

See the equipment grounding conductor 250.122 reference for the sizing table.

Array bonding

Module frames and rails must be bonded into a continuous path:

• Use listed bonding hardware — WEEBs (washer-type bonding jumpers), grounding lugs, or clips rated for the module frame and rail.
• Many racking systems are listed for integrated bonding, carrying the bond through the rail so you don't jumper every module — follow the manufacturer's listing exactly.
• Keep the bonding conductor continuous; splices must be irreversible or listed.

The grounding electrode conductor (GEC)

The GEC connects the system grounding point to the grounding electrode:

• Sized from NEC 250.166 (DC) or 250.66 (AC) depending on the system.
• The PV system generally bonds to the home's existing grounding electrode system rather than creating an isolated one.
• If a supplemental electrode is added, it must be bonded to the existing electrode system — never left as a separate island.

Common field mistakes

Grounding is where clean-looking installs quietly fail inspection. Watch for:

• Dissimilar metals: copper on aluminum without a listed connector invites corrosion; use hardware rated for the metals you're joining.
• Paint and anodizing: module frames and rails are non-conductive on the surface, so bonding must bite through the coating with listed teeth or star washers.
• Undersized or missing EGC: every current-carrying circuit needs its EGC; a reviewer will flag a segment that lost it.
• Isolated supplemental rod: a new ground rod that isn't bonded back to the existing electrode system is a violation, not a bonus.

What a reviewer checks

On the one-line, the reviewer looks for the EGC in every circuit, the bonding method for the array, the GEC to the electrode, and that any added electrode is bonded to the existing system. Missing or unsized grounding conductors are a common correction.

Grounding details vary by racking listing and AHJ, so follow your equipment's instructions and confirm local requirements. A licensed electrician or PE must review and stamp the final design. To see how grounding fits the whole package, read what is in a solar permit set or browse the reference library.

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.