Grounding fails more DIY solar inspections than any other single item, which is revealing: it is invisible when done right, easy to do incompletely, and it is what stands between a fault and someone touching an energised metal frame. It is also genuinely confusing, because the word covers two different jobs.
Two jobs, one word
Equipment grounding connects every metal part that could accidentally become energised — panel frames, racking, enclosures, inverter chassis — back to your electrical system's ground, so a fault produces enough current to trip protection instead of sitting there waiting for a hand.
System grounding (or bonding) intentionally connects one current-carrying conductor to earth to establish a voltage reference. Most modern grid-tied inverters are transformerless and ungrounded on the DC side, so this often does not apply — but equipment grounding always does.
Getting these confused is why people bond things that should float, or leave floating things that should be bonded. When in doubt, follow the inverter manufacturer's wiring diagram: it tells you which configuration the equipment expects.
The grounding path, end to end
- Panel frames to racking. Most racking systems bond through the mounting clamps as you tighten them — but only with the correct clamps in the correct places. If yours does not, you need separate bonding jumpers between every module.
- Racking rails bonded together, so a multi-rail array is one continuous conductive assembly rather than isolated sections.
- Racking to the equipment grounding conductor, using a listed lay-in lug and a conductor sized per code for the circuit's overcurrent device.
- Enclosures and the inverter chassis onto the same conductor.
- Back to the main service grounding electrode system. Everything ends at one point — this is what makes it a system rather than several separate grounds.
The most common failures
- Assuming the racking bonds itself without confirming the manufacturer's listing and using their specified clamps in their specified positions
- Painted or anodised surfaces breaking continuity — bonding hardware must bite through the coating to reach bare metal, which is what star washers and listed bonding clips are for
- A separate ground rod at the array that never connects back to the main service. This creates a difference of potential rather than removing one, and is worse than useless
- Undersized grounding conductors, sized by guess rather than to the code table
- Ordinary hardware store lugs instead of listed grounding lugs rated for the application
- Mixed metals — copper against aluminium corrodes over time and the connection quietly degrades until it is no longer a connection
Ground-mounted arrays
A ground mount still bonds back to the main service grounding electrode system. It may additionally require a local grounding electrode depending on your code edition and the array's distance from the building, but that is in addition to the main path, never instead of it. Isolated grounds are one of the more dangerous DIY misunderstandings.
Verify it, do not assume it
Continuity testing with a multimeter — from a panel frame all the way back to the service ground — takes minutes and is the single best-value check you can run before an inspection. Test every module, not a sample: the whole point is that there is no gap anywhere in the path.
Photograph the bonding connections before anything is covered. If a question comes up at inspection or in a warranty claim years later, the photos answer it.
Requirements vary by adopted code edition and local amendment, so treat this as the common pattern rather than a specification for your jurisdiction — your inspector and your adopted code are the authority. Grounding is also a strong candidate for the one-hour electrician review, since it is exactly what an experienced eye catches in minutes. What inspectors look at overall is in the inspection guide.