Smart Inverter Working Group

The Smart Inverter Working Group (SIWG) grew out of a collaboration between the CPUC and California Energy Commission (CEC) in early 2013 that identified the development of advanced inverter functionality as an important strategy to mitigate the impact of high penetrations of distributed energy resources (DERs).The SIWG has pursued development of advanced inverter functionality over three phases. Phase 1 considered autonomous functions that all inverter-connected DERs in California will be required to perform.Phase 2 considered the default protocols for communications between IOUs, DERs, and DER aggregators. Phase 3 is currently considering additional advanced inverter functionality that may or may not require communications.

For more information on the SIWG, please contact Sophie Meyer at .



Capability Required by: 

Requirement Detailed in: 

Phase 1 Autonomous Functions 

September 8, 2017

Section Hh of Electric Tariff Rule 21 (Links to each utility’s Rule 21 can be found here).

Phase 2 Communication Protocols

August 22, 2019

Section Hh of Electric Tariff Rule 21 (Links to each utility’s Rule 21 can be found here).

Phase 3 Advanced Functions 


Exact requirements have not yet been determined. SIWG recommendations on Phase 3 can be found here.


CPUC Staff Proposal on Power Priority Setting of Smart Inverters

On Thursday, July 27, Energy Division issued a Staff Proposal on Power Setting of Smart Inverters on how the investor-owned utilities (IOUs) can modify the Rule 21 tariffs to transition all grid-connected inverters from reactive power priority to real power priority.  Below are the written comments received by Energy Division.  At this time, Commission Staff does not see the need for reply comments but will consider allowing reply comments if parties request the opportunity to submit them.


Upcoming Meetings

The CPUC invites you to participate in a series of SIWG weekly calls to address requirements pursuant to Resolutions E-4898 and E-4920.  The objective of these calls is to consult with the California investor-owned utilities (IOUs) on the tariff revisions that they are required to file through advice letters in October and December of 2018 and to plan for the implementation of Smart Inverter Phase 2 and 3 requirements.  Additional topics may be proposed and discussed.  Regular calls take place between 1 and 2:30 PM PST on Thursdays.

Please contact Sophie Meyer at for meeting details.

Past Workshops

 Wednesday, August 15, 2016 - SIWG Workshop to Address Requirements under Resolutions E-4898 and E-4920  

SIWG History

SIWG materials, presentations from the previous workshops and links to the video webcast can be found on the CEC’s Rule 21 Smart Inverter Working Group website.

SIWG Recommendations for Phase 3 Advanced Functions

The SIWG released it updated Phase 3 Recommendations in March 2017.  Previousely, the SIWG hosted webinar meetings to develop these recommendations as well as discuss coordination issues between the SIWG,  related CPUC proceeding and relevant organizations (California Energy Commission, Institute of Electronic and Electrical Engineers (IEEE), Underwriters Laboratory, etc.).

SIWG Recommendations for Phase 2 Communication Protocols

The SIWG released its Phase 2 Recommendations for Utility Communications with Distributed Energy Resources (DER)Systems with Smart Inverters in February 2015. The IOUs submitted Rule 21 tariff revisions incorporating the Phase 2 recommendations on December 20, 2016.  The Commission's Energy Division subsequently approved the revisions.  The implementation of the recommendations is available through each utility's Rule 21, interconnection technical handbook, and an IEEE 2030.5 Common Smart Inverter Profile (CSIP) Implementation guide.

SIWG Recommendations for Phase 1 Autonomous Functions

In D.14-12-035, the Commission adopted seven functions that smart inverters must perform autonomously. The seven Phase 1 functions will be mandatory for all interconnecting DERs on September 8, 2017.   D14-12-035 was informed by the SIWG's Recommendations for Updating the Technical Requirements for Inverters in Distributed Energy Resources document. 

Petition for Modification of Resolutions E-4898 and E-4832

On February 11, 2019, CALSSA submitted the Petition of the California Solar & Storage Association for Modification of Resolution E-4832 and Resolution E-4898 to the CPUC Energy Division.  This Petition addresses the Smart Inverter Phase 2 communications requirments and Functions 1 (Monitor Key DER Data) and 8 (Scheduling Power Values and Modes) of Smart Inverter Phase 3.  More information and links to the Petition and associated resources can be found here.

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