Do I need a GFCI outlet for plug-in solar?

Yes, a GFCI is required for any outdoor installation. Plug-in solar is almost always installed outdoors on a balcony, patio, fence or roof, and outdoor receptacles have required ground-fault circuit interrupter protection under the National Electrical Code for decades.

This is not specific to solar. Any outdoor outlet should have it. If the outlet you plan to use is not GFCI-protected, you have two options: replace the receptacle with a GFCI receptacle, or fit a GFCI breaker in your electrical panel. Both are standard work for an electrician, and the receptacle swap is inexpensive.

If your outdoor outlet predates the requirement, treat this as an upgrade worth making on its own merits, whatever you plug into it.

Can I use a light socket adapter instead of an outlet?

No. Lighting circuits are wired for the wattage a fixture draws, and the gauge is generally not rated for more. Using a socket adapter risks heating the wiring, and lighting circuits are rarely GFCI-protected.

Do GFCI devices ever fail?

They do, and they are designed to fail safe. A failed GFCI should stop passing power rather than pass it unprotected. Test yours with the built-in test button periodically, as you would any other GFCI in the house.

Doesn't the microinverter already have safety shutdown built in?

It has rapid shutdown, which addresses a different risk. GFCI protects against ground faults reaching a person. The two are complementary, not alternatives.

Summarized from an ongoing conversation in the Bright Saver Community, where early adopters share what they are learning as they install.