Plug in solar and GFIs

[peatmoss]

I'm seeing a lot of ads for plug in solar these days. The companies that promote it are saying plug your system into a GFI outlet. There is an old thread on here but its not really conclusive. https://forums.mikeholt.com/threads/can-you-back-feed-a-gfci-breaker-in-a-sub-panel.92576/

The schematic of a GFI shows there is a current sense coil over both hot and neutral lines. The way they work is if there is current outside these lines on return a current is generated in the coil. If you backfeed a GFI I don't see how it knows the difference as long as there is no current leakage.

What a ground fault circuit interrupter does and what it does not do | EEP

A ground fault circuit interrupter (GFCI) monitors the current balance between the ungrounded “hot” conductor and the grounded conductor.

electrical-engineering-portal.com

Anyone have experience or thoughts on this? How about GIF breakers?

 

[don_resqcapt19]

I approved this since it is not asking for DIY how to information.

 

[jaggedben]

I don't believe plug-in solar is actually legal anywhere in the US under utility rules, notwithstanding what ads might tell you. It's legal in parts of Europe, maybe it should be here too, but it's not.

As far as backfeeding a GFCI, there has long been the requirement in the NEC that circuit breakers be suitable for backfeed. (705.30(D) in the 2026 NEC). GFCIs have not typically been suitable for backfeed and a manufacturer's instruction that runs afoul of the NEC in this way is prohibited by the NEC and may not pass an inspection.

There are other safety issues that would make safe plug-in solar not really plug-in, as well.

The products you are looking at, do they say they're listed to UL1741? I have heard of some plug-in products maybe getting listed but I'm honestly a bit baffled at how that can be.