Rule 21 refers to the generator interconnection requirements of each California Investor-Owned Utility (IOU). A years-long process has been underway to update Rule 21 with “smart inverter” requirements. Rule 21 requires inverters to have new grid support functions and a new certification under UL 1741 SA. Each new inverter also gets a new nameplate label…
Fronius completes Rule 21 inverter certification
