Here in the USA the NEC (National Electrical Code) states that ALL devices connected to the electricity of a structure MUST be listed to UL by a NRTL (National Reliability Testing Laboritory) which is in the NRTL program operated by the U.S. OSHA (Occupational Safety Hazards Agency)
There is no differentiation between grid tie and off grid. The requirement is for all electricity used in any building which falls under the building code to have all components be listed for the specific applications.
It is not relevant that some other testing agency tests some hardware to be “compliant with the U.L.“ The wording is
“Listed to UL (relevant standard) by an NRTL”
Fred’s garage might be able to test to UL standards but if they are not accepted by U.S. OSHA’s NRTL program it does not mean squat.......
Go look at some major players in the market......for instance my Midnight Classic 150 is “Listed to UL 1741 by ETL”
The Outback Radian Inverter is “Listed to UL 1741 SA by ETL” grid tie/hybird off grid)
The MagnaSine MS4024AE inverter/charger is “Listed to UL 1741 by ETL” (off grid)
ETL (Electrical Testing Laboratories) is an accepted NRTL as listed by OSHA
There are many others such as European T.U.V. is a US OSHA NRTL and as such can and does test and list european gear to U.L.
Do make sure that the testing agency is a US OSHA NRTL for any system used here in the USA and most other countries do have their own standards as to the testing requirements for devices. Canada for instance does have a very similar program for testing verifications, as does Great Britain and Germany
I have seen numerous instances in my local jurisdictions where building inspectors have “Red Tagged“ homes where there are non UL listed components in the electrical systems. (Requiring the power company to remove power from said building, AND remove “occupancy permit”)
Here in California all building inspectors must verify that all solar components are listed with the California Public Utilities Commission. If your inverter, charger, or solar panels are not on the state approved devices list you will not get a “OK TO CONNECT” issued to the local utility issued by the local inspector
I have a pile of offshore gear that I have been paid to remove from buildings to satisfy the local code enforcement department to clear the red tag and permit building occupancy, including the “Fution” AKA Best Sun Powerwall which I was paid to remove from a home in Scotts Valley California (my intervention on this case prevented it from going to the insurance companies and the building department).
Read , trust, but absolutely verify before you throw monies down that rabbit hole.....
Additionally most all insurance policies do require full NEC code complianc