Fronius inverters now California Rule 21 compliant

Fronius USA received UL certification for California’s Rule 21 inverter requirements, which are required in California for new Net Energy Metering (NEM) applications from September 8.

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What’s Rule 21 again?

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 that identifies it as a “Grid Support Utility Interactive Inverter.”

How California’s Rule 21 inverter requirements expand grid capacity, limit energy (revenue) generation

New smart functions, such as voltage and frequency ride-through or soft start ramp rate, will pave the way for further solar penetration into the California grid and help to better manage the fluctuations caused by distributed energy resources (DER). These new functions have a stabilizing effect on the grid as more DER is added to it. Fronius has always been a driving force when it comes to inverters’ Grid Support Functions and has years of experience from highly solar-penetrated markets such as Germany or Italy.

The proper Rule 21 settings on Fronius inverters are easy to apply for installers, who simply select the “CAL” setup upon commissioning. “While adding more and more functionalities to the inverter, we want to make the adoption of Rule 21 as easy as possible for our installers”, says Michael Mendik, Head of Solution Management at Fronius USA.

Fronius has received certification for the Fronius Primo 3.8 – 8.2 kW residential inverters, and Fronius Symo 10.0 – 24.0 480V commercial inverters. These inverters are available with Rule 21 compliant software as of August 14th. The Fronius Primo 10 – 15 kW inverters as well as the 208V version of the Fronius Symo will be certified in Q4. Fronius will announce these dates as soon as possible.

— Solar Builder magazine


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