Electric Rule 21 is a tariff that describes the interconnection, operating and metering requirements for generation facilities to be connected to a utility’s distribution system, over which the California Public Utilities Commission (CPUC) has jurisdiction. The Rule 21 tariff for each of California’s large investor owned utilities (IOUs) is available on each IOU’s website. Note that the posted Rule 21 may not reflect updates to the tariff that may be pending before the CPUC:
The CPUC's open interconnection proceeding is R.11-09-011. For information or to discuss a matter related to distribution system interconnection, contact Marc Monbouquette, Energy Division, at firstname.lastname@example.org or 415-355-5504.
Smart Inverter Working Group – Phase 2 Communication Protocols
The Smart Inverter Working Group released its Phase 2 recommendations for DER communication protocols in February 2015. The CPUC Energy Division is currently working with the IOUs to implement these recommendations in Rule 21, the IOUs’ interconnection technical handbooks, and an IEEE 2030.5 implementation guide. For more information, please contact Marc Monbouquette at the contact info listed above.
SIWG Phase 2 Communications Recommendations – February 28, 2015
Rule 21 updated to enable Smart Inverters!
Dec 3 Workshop: on the Development of Storage and Interconnection Policies
Dec 4 Workshop: on the Development of Cost Certainty Policies for the Interconnection Process
Q4 Interconnection Quarterly Reports
Q3 Interconnection Quarterly Reports
Oct 27 Smart Inverter Working Group Phase II Communications Protocols Workshop information:
Recommendations for Utility Communications with Distributed Energy Resources (DER) Systems with Smart Inverters- Smart Inverter Working Group Phase 2 Recommendations
Monday, October 27, 2014 Time: 10:00 a.m. ‐ 4:30 p.m. (Pacific Time)
Location: CPUC Auditorium, 505 Van Ness Avenue, San Francisco, CA 94102
This workshop will be available via live video webcast at:
To start the WebEx online meeting:
Meeting Number: 745 848 621
Meeting Password: inverter
SIWG Phase 2 Communications Concepts and Status
SIWG CPUC Workshop Panels: Discussion Questions
The Integration of Distribution Level Generation & Storage into the Grid - Problems and Solutions - Grid Planning and Reliability - Policy Paper
Written by: Robert Elliott
Rule 21 Interconnection ‐ Quarterly Report for Q2 2014 – Public Version
Rule 21 comments received on September 12, 2014
On July 29, 2014, an ALJ Ruling introduced two staff proposals into the Interconnection Proceeding to assist with record development. The Ruling set a schedule for comments and reply comments and also calendared a prehearing conference on the two documents. Please find the Ruling and two reports here:
1) Issues, Priorities, and Recommendations for Energy Storage Interconnection
2) Cost Certainty for the Interconnection Process
Parties to the interconnection proceeding may submit Comments by September 12.
Parties to the interconnection proceeding may submit Reply Comments by September 26.
A prehearing conference on the two documents is set for October 2, 2014 at 10 a.m.
For information on becoming a party or submitting comments, please contact the CPUC Public Advisor
On July 18, 2014, thanks to an assist from SDG&E, the Smart Inverter Working Group (SIWG) Motions into Interconnection Proceeding Phase II Communications Scope of Work and Delivery Date for Recommendations
Also on July, 18, 2014, utilities jointly submit Draft Rule 21 Tariff language enabling the SIWG Phase I Autonomous Functionalities Parties to the Interconnection Proceeding may provide comments until August 18, 2014.
For information on becoming a party or submitting comments, please contact the CPUC Public Advisor
May 13, 2014: Assigned Commissioner’s Amended Scoping Memo and Ruling
Rule 21 Interconnection - Quarterly Report for Q1 2014 - Public Version
Smart Inverter Working Group Recommendations for Rule 21 Updates:
Recommendations for Updating the Technical Requirements for Inverters in Distributed Energy Resources
Interconnection & Energy Storage Meeting
10:00am – 2:30 pm
Phone in: 1-866-758-1675
Pass Code: 7646128#
Please note that the Rule 21 website is under construction and will be updated shortly.
September 25, 2012: Assigned Commission Phase II Scoping Memo Issued
Assigned Commissioner Michel P. Florio issued a Phase II Scoping Memo in R,11-09-011, setting out the high-priority issues to achieve the Commission's goal of ensuring a timely, non-discriminatory, cost-effective, and transparent process for interconnection to the utility distribution system.
September 13, 2012: Rule 21 Settlement Approved
In Decision 12-09-018 the Commission approved the full set of reforms to Rule 21 proposed via a multi-party settlement. The Commission anticipates that the significant reforms achieved in Rule 21 will advance the Commission's goals of ensuring a timely, non-discriminatory, cost-effective, and transparent interconnection process for distributed generation in California.
March 16, 2012: Rule 21 Settlement filed
On March 16, 2012, fourteen parties to the Distribtuion System Interconnection Settlement Process filed a settlement in CPUC Rulemaking (R.)11-09-011.
The settling parties are: Aloha Systems, California Farm Bureau Federation, Center for Energy Efficiency and Renewable Technologies, Clean Coalition, Interstate Renewable Energy Council, Pacifc Gas and Electric Company, San Diego Gas & Electric Company, Sierra Club, solar Energy Industries Association, Southern California Edison, SunEdison, Sunlight Partners, Sustainable Conservation, and Vote Solar Initiative.
The centerpiece of the settlement is significantly reformed CPUC-jursidictional Rule 21 interconnection tariff. Upon launching the settlement process for Rule 21 in August 2011, the CPUC's goal was to craft transparent rules that provide a clear, predictable path to interconnection for distributed generation while maintaining the safety and reliability of the electric grid.
See here for the full Motion for Approval of Settlement Agreement Revising Distribution Level Interconnection Rules and Regulations.
September 22, 2011: CPUC approves Distribution Interconnection Proceeding
The CPUC approved an OIR (R.11-09-011) to “review the rules and regulations governing interconnecting generation and storage resources to the electric distribution systems of Pacific Gas and Electric Company (PG&E), Southern California Edison Company (SCE), and San Diego Gas & Electric Company (SDG&E).” The OIR is the procedural forum for the Distribution System Interconnection Settlement Process.
August 23, 2011: Distribution System Interconnection Settlement Process
The CPUC launched a multi-party Distribution System Interconnection Settlement Process intended to reach a global settlement on issues regarding distributed generation interconnection to the investor-owned utility distribution system in California. The Settlement Process is subject to confidentiality rules, pursuant to CPUC Rule 12, and FERC Rule 602.
Rule 21 Working Group
The Rule 21 Working Group has served since 2000 as the source of ideas for maintaining and updating technical and other standards within the Rule 21 tariff. The Rule 21 Working Group is not meeting in its usual format while the Distribution System Interconnection Settlement Process is underway. Future public meetings of the Rule 21 Working Group will be noticed in the Commission’s Daily Calendar.
August 2011 Working Group Workshops
- August 19, 2011, 9:00 a.m.-12:00 p.m., CPUC Auditorium: Rule 21 Working Group Workshop. Off-site participation: This workshop will be available via video webcast in real-time and archived. Presentation available here.
- August 19, 2011, 1:00-4:00 p.m., CPUC Courtyard Room: Rule 21 Working Group Technical Subcommittee Meeting. Offsite participation will be available by phone. Phone-in information will be sent only to participants who have completed an rsvp form at the link below. Presentation available here.
- August 23, 2011, 1:00-4:00 p.m., CPUC Courtyard Room: Rule 21 Working Group Business Practices Subcommittee Meeting. Offsite participation will be available by phone. Phone-in information will be sent only to participants who have completed an rsvp form at the link below. Presentation available here.
Download the full agenda for the above meetings
April 2011 Working Group Workshops
CPUC held a Rule 21 Working Group Workshop Friday, April 29, 2011 at the CPUC Auditorium.
Download a printable agenda here
Workshop presentation materials:
About the Rule 21 Working Group
The intent of the Rule 21 Working Group is to build consensus among the CPUC, IOUs, generators, and advocates for Rule 21 reforms to meet the technical needs and policy goals of interconnecting distributed generation. The Rule 21 Working Group succeeded at this goal in its past work, making California's Rule 21 a national model tariff establishing metering and operating standards for interconnecting distributed generation resources. Following three years of extensive change in the statutory, technological, and generator context, however, Rule 21 is widely agreed to be in need of reconsideration.
The purpose of this kickoff meeting is to initiate discussion of the issues emerging under Rule 21 that may be hindering the achievement of California's distributed generation goals. Below are examples of such issues that CPUC has identified:
- Need for transparency in terms of processing, queue information, and customer application information;
- Need for review and potential reconsideration of technical screens within Rule 21 to ensure that the appropriate issues are being studied;
- Need for articulation of cost allocation methodology where network upgrades are required;
- Need for review of utility tariff consistency with each other and with state law;
- Need for additional standard interconnection agreements to accommodate the different types of distributed generation projects anticipated to come online.
June 20 2008: Workshop on Rule 21
On June 20, 2008, the California Public Utilities Commission (CPUC) held a workshop on the topic of the Rule 21 interconnection standard. The primary focus of the workshop was to discuss the transition of Rule 21 oversight from the California Energy Commission (CEC) to the CPUC.
A more detailed history of the Rule 21 Working Group is available on the CEC website. For more information about past Rule 21 Working Group activities visit http://rule21.ca.gov/.