California Rule 21

What you need to know to be in compliance

What you need to know about CA Rule 21

Enphase Rule 21 compliance is achieved with the application of an Enphase Rule 21 compatible grid profile to certified hardware.

  • CA Rule21 201902 VV VW FW grid profile defines utility approved operating parameters for those California Enphase systems whose application for interconnection was submitted on or after February 22, 2019. This profile was made available on February 22 deadline and meets all previously adopted CA Rule 21 requirements and adds two new functions, Volt/Watt (VW) and Frequency/Watt (FW), as required by CPUC Resolution E-4898.
  • CA Rule21 201807 VV w/RPP grid profile defines utility approved operating parameters for those California Enphase system whose application for interconnection was submitted after July 26, 2018 as required by CPUC Resolution E-4920.
  • CA Rule21 201709 grid profile defines utility approved operating parameters for those California Enphase systems whose application for interconnection was submitted after September 8, 2017.

Use the resources below to learn how to apply the appropriate grid profile to your certified hardware and how to generate a compliance report for your utility.

 


 

Certified hardware

All IQ platform Microinverters are certified for Rule 21 requirements taking effect February 22, 2019. S-Series Microinverters will not be compliant with February 22, 2019 requirements. Visit the CEC website here for a simplified listing of compliant products. Certificates of compliance can be found at the following links:

Grid profiles may be applied any time before, during, or after installation and requires Envoy software version 4.10 or greater. Learn how to update the Envoy onsite using the Installer Toolkit here.

Prior to Install: This is the recommended approach. Without ever leaving the office, simply select the appropriate grid profile on the site activation form, and the profile will be applied to the microinverters when the site Envoy connects to Enlighten. Watch this video to learn how to apply the grid profile using the activation form.

During Install: If the profile has not already been set prior to the installation, set it during the installation using the Installer Toolkit mobile app. Watch this video to learn how to apply the profile using the Installer Toolkit and how to generate a Summary Report to demonstrate Rule 21 compliance.

After Install: Have systems that have already been installed been updated to the Rule 21 profile? You can apply the appropriate grid profile and run the report at any time simply by updating the system activation form. Watch this video to learn how to apply the grid profile using the activation form.

 


 

Compliance reporting

A utility compliance report can be generated at any time. The instructions for this are included in the profile application videos above.

 


 

Learn more about Rule 21

Want to learn more about Rule 21? Read our blog post on the topic here or download our latest Technical Brief here.

Want to learn more about California Rule 21? Attend an upcoming Rule 21 webinar.

Have a specific question not answered above? Jump to our FAQs below.

The PUC published new compliance dates in their (draft) resolution E-5000 of July 11, 2019. Download the letter here. Compliance dates as defined in draft resolution E-5000 are also listed in the table below.

CA Rule 21

Phase
Function Effective Date
2 IEEE 2030.5 Communication Certificate August 22, 2019
3 Function 1: Monitor Key DER Data January 22, 2020
3 Function 2: DER Disconnect/ Reconnect January 22, 2020
3 Function 3: Limit Maximum Active Power January 22, 2020
3 Function 4: Set Active power To be determined*
3 Function 5: Frequency Watt February 22, 2019
3 Function 6: Volt Watt February 22, 2019
3 Function 7: Dynamic Reactive Support To be determined*
3 Function 8: Scheduling Power Values and Modes January 22, 2020

* 12 months after approval of a nationally recognized standard that includes the function.


 

California Rule 21 FAQs

1.  Do smaller California utilities like Silicon Valley Power (SVP) in Santa Clara or City of Palo Alto Utilities (CPAU) require Rule 21 compliance?

Requirements vary by utility. Installers should contact the utility directly with specific compliance questions.

2.  How are AC-coupled energy storage interactive systems interpreted from an AHJ standpoint? Must both the grid-tied micro and energy storage inverter comply?

Yes, California Rule 21 applies to all inverters interconnected to the grid whether they are connected to a battery or solar module.

3.  Is there any data on curtailment that functions 5 and 6, Frequency-Watt and Volt Watt, may impose on production?

The Volt-Watt function was designed to work together with Volt-Var as a “belt and suspender” approach. Both functions are based on the AC grid voltage.

When voltage is higher than nominal the VV curve starts to take effect first with the inflection point set to 1.033 PU. As voltage increases the output VArs continue to increase (more absorbing, more under-excited) until at 1.07 PU the VArs saturate at 0.30 %VAr max absorbing/under-excited. Similarly, as voltage decreases, the vars increase until they saturate to 0.3 %VAr Max generating/over-excited at 0.92 PU. See the graphs below.

VW only starts to take effect when the voltage increases beyond 1.06 PU, which is past ANSI C84.1 Range A. In practical terms VV is like the “belt” and VW is like the “suspenders.” Only when the voltages increase way out of range, will VW take effect. And as voltage is increasing the VV curve will help regulate the voltage back down by absorbing VArs. The voltage regulating effect of VV and VW will help keep the inverter from tripping. As the voltage increases, VV and VW will help reduce the voltage and tend to keep the inverter from tripping.

So how much power is lost with these curves in place? HECO (Hawaiin Electric Company) hired NREL to perform a study based on simulation and actual field measurements. In fact, Enphase participated in this study by supplying actual field data through Enlighten. NREL published the results found in Advanced Inverter Voltage Controls: Simulation and Field Pilot Findings. The paper is very complicated, but in summary the VV curve had very little effect on energy curtailment. Also because of the voltage regulating effect of the VV and VW curve the action of the functions helped stabilize the voltage. Without it the system may have tripped. With only VV enabled the net energy gain was +2.44%. That’s an increase in generation.  With both VV and VW enabled, NREL found an increase in generation of +2.74%.