Does UL1741 Rule 21 only apply to solar inverters in California, or is it Nationwide?

Looking to buy some used sunnyboy inverters about 7 years old, however sunny design software says that these older inverters do not meet RULE 21 standards.
From my limited research Rule 21 only applies to California. 
Duke Energy my provider in NC states that I must install UL1741 compliant inverters. 
I have emailed them asking if Rule 21 needs to be met. Anyone know?


  • Dave AngeliniDave Angelini Solar Expert Posts: 6,034 ✭✭✭✭✭
    Rule 21 is an intelligent way to future proof micro grids and remote power systems. Other states will start using it. As it is now in California, Rule 21 allows state incentives to pay home owners for battery purchase. In the case of the Schneider XW Pro inverter, it added large amounts memory to run the various strategies that rule 21 requires.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
    E-mail [email protected]

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