Are you Ready to Achieve Compliance of California Rule 21 Reactive Power Priority Requirement?

CA Rule 21 Phase1 new requirements will include a Reactive Power Priority setting starting Thursday, July 26.  UL has certified SMA inverters as compliant with this new regulation.

Tech Tip: Configuration of Sunny Boy for CA Rule 21 Phase 1 Settings

Since September 2017, California’s three IOUs require you to adjust grid-tied inverters installed in their service territories to enable CA Rule 21 Phase 1 settings. You may find a list of equipment capable of meeting these requirements by visiting

On April 27, 2018, the California Public Utilities Commission – Energy Division issued Resolution E‐4920 incorporating a new requirement that will go in effect on July 26, 2018. The additional requirement ensures that inverters also give priority to reactive power under conditions where the inverter would be required to curtail active power to provide the desired reactive power.

SMA’s residential inverter lines, the Sunny Boy US-40 and Sunny Boy Storage US-10, and commercial string inverter lines, the Sunny Tripower TL-US-10 and Sunny Tripower CORE1-US, will prioritize reactive power when you correctly enable the required CA Rule 21 Phase 1 settings.

UL evaluated which products provide the reactive power priority functionality as defined in CPUC Resolution E‐4920, and have issued a list of the UL certified grid support utility interactive products. Page three lists the SMA models and in columns, two and three denotes that the specified devices comply fully when configured correctly at installation for CA Rule 21 Phase 1 settings.

UL Letter - Reactive Power Priority Inverters List

California Solar & Storage Association has also issued a list of inverters that were approved as compliant with the new standard, which also includes these SMA inverters.

You can review the CA Rule 21 Phase 1 configuration files (“.bck” files) for the Sunny Boy US-40 family and Sunny Tripower CORE1-US. To enable all required CA Rule 21 Phase 1 functions correctly you just need the appropriate “.bck” file to be loaded onto the inverter at commissioning; this includes reactive power priority. For the Sunny Boy, Sunny Boy Storage, and CORE1 families, you can easily accomplish this by accessing the inverter’s user interface on its self-hosted Wi-Fi network and loading the file onto the inverter. (Minimum FW version needed: Sunny Boy US-40 requires 2.03.01.R or higher, Sunny Tripower CORE1-US requires 1.01.19.R or higher, Sunny Tripower TL-US-10 requires 2.83.03.R or higher).

Additional resources are available for the Tripower TL-US-10 line and the Sunny Boy Storage US-10 line. For instructions on utilizing the CA Rule 21 settings file on a Sunny Boy US-40 device, watch this Tech-Tip video.

  1. Dan Marohl
    Dan Marohl says:

    I have a 7700TL-US-22, can it be made compliant. I want to use it on a second house install without buying a new inverter.

Leave a Reply
Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published.

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>