Quick definition
Solar wiring is designed to keep current flowing along a controlled path, from the panels, through the wiring, to the inverter. A ground fault happens when current escapes that intended path and finds an unintended route into something grounded, like the metal racking frame, usually because insulation somewhere in the system has been damaged or compromised.
Every grid-tied inverter includes ground fault protection specifically designed to detect this and shut the system down before it becomes dangerous.
At a glance: ground fault protection is a required safety feature on virtually all modern grid-tied inverters sold in the US and Canada.
Why it matters
A ground fault isn't just a performance issue, it's a real electrical safety hazard. Current escaping into a metal racking frame or roof structure can create a shock risk for anyone touching that structure, and in some cases can generate enough heat at the fault point to pose a fire risk. This is exactly why the National Electrical Code has required ground-fault protection on rooftop PV systems since Section 690.5 was first added in 1987, specifically to reduce fire hazards rather than to address shock risk, and inverters are built to automatically shut the system down the moment a fault is detected rather than continuing to operate with a compromised wiring path.
Most ground faults trace back to something physical going wrong with wiring insulation over time: sun and weather exposure gradually breaking down cable jacket material, water finding its way into a supposedly sealed connector, a rodent chewing through a cable, or a wire that got pinched or abraded during installation. These aren't usually sudden, dramatic failures, they're often slow degradation that eventually crosses a threshold the inverter's protection detects. For the numbers behind Ground fault, the solar inverter size calculator in our Inverters & Equipment section walks through the calculation step by step.
When ground fault protection trips, the system stops producing power until the fault is found and repaired. This makes a ground fault indication a real, actionable maintenance issue rather than something to reset and ignore, since restarting a system without fixing the underlying wiring problem just risks tripping the protection again, or worse, not tripping it the next time. Ground-fault protection for rooftop PV is a National Electrical Code requirement, and the Building America Solution Center's NEC library explains how the code treats PV systems.
Where you'll see this
The connector and wiring inspection cost estimator helps budget for the kind of professional inspection that catches wiring issues before they escalate into a ground fault.
If a ground fault has already tripped the system and the inverter itself needs diagnosis or repair, the inverter failure repair cost estimator gives a starting cost range.
Degraded wiring that's severe enough to cause a ground fault is often also quietly costing production well before it trips protection, which the wiring loss output calculator can help quantify.
This term comes up in inverter error codes and fault indicators, in system troubleshooting after an unexpected shutdown, and in routine wiring inspections meant to catch insulation damage before it causes a fault. The National Fire Protection Association publishes the National Electrical Code itself, which sets the ground-fault protection rules installers must follow.
Related terms
Frequently asked
A ground fault itself is a real safety concern, which is exactly why systems are required to have ground fault protection that shuts the system down automatically when one is detected. The protection working as intended is a sign the safety system is doing its job, not a sign of a bigger hidden problem, though the underlying fault still needs to be found and fixed.
Damaged wire insulation, water intrusion into a junction box or connector, rodent damage to cables, or a physically pinched or worn wire are all common causes. Age and weather exposure over many years can also gradually degrade insulation enough to create a fault.
No. Most inverters are designed to automatically shut down when ground fault protection detects a fault, and the system shouldn't be manually restarted until the underlying cause is found and repaired by a qualified technician.
A technician typically uses an insulation resistance tester (often called a megger) and a systematic process of isolating strings or sections of the array to narrow down where the fault is occurring, since the general fault indication alone doesn't usually pinpoint the exact location. IEC 62446-1, the international standard for PV system testing and documentation, specifies the test voltages and minimum acceptable resistance readings used to judge whether a string's insulation has degraded enough to be the culprit.