Interconnecting Generation under Rule 21

New-generation projects considering interconnection to SCE’s distribution system under Rule 21 can find useful information regarding the interconnection process and the technical requirements applicable to your project at the following links:

• SCE’s Rule 21 This is the most important reference. It describes the interconnection, operating, and metering requirements for generation facilities to be connected to SCE’s distribution system.
• SCE’s Interconnection Handbook provides information regarding technical requirements for installing and operating your generation system in a safe and reliable manner.
• SCE’s Electrical Service Requirements (ESR) manual provides guidance and instructions pertaining to electrical service connections. Its purpose is to assist electrical contractors, engineers, architects, and manufacturers engaged in the installation of electrical service wiring and equipment.
• Project uses a UL Certified Power Control System which has been pre-approved by SCE. A list of approved UL Certified Power Control Systems can be found at: Linked here
• Project uses an inverter that has been pre-approved by SCE. A list of approved inverters can be found: Linked here
• To find out if the circuit you have chosen to interconnect your project is on SCE’s transmission or distribution system, please send a question with the identified pole number and the voltage (kV) of the line selected to interconnectionQA@sce.com.
• FAQs for SCE’s Rule 21
• A Pre-Application Report provides technical information about the current conditions of a specific circuit a customer may be interested in interconnecting a project. Please review the section below, Rule 21 Pre-Application Report Request, for more information on how to obtain this report.
• Self-Generation Projects. Customers who produce their own power from generation systems are eligible to request interconnection service under Rule 21. Please visit our Programs for Self-Generation for more information about the various programs available to help you self-generate your power.
• Projects seeking to participate in the SBP program should visit the Solar Billing Plan webpage for information regarding the application for interconnection and the SBP process.
• Please see the Simple and Complex Interconnection Metering Requirements.

Additional Information

Please consult with your local planning or permitting authority to verify any local permitting requirements. SCE does not provide permitting services.

Pursuant to the CPUC Energy Division’s acceptance of SCE Advice Letter 4824-E/E-A/E-B/E-C, effective August 29, 2023, Rule 21 applicants are required to use inverters that comply with UL 1741 SB requirements as specified in Section Hh of SCE’s Rule 21 tariff. Additional information is noted toward the top of this page. 

Please see the Instructions Sheet and Inverter Information Submittal form below:

• Instructions Sheet
• Inverter Information Submittal

The following guidelines were developed during 2024 to clarify helpful and efficient practices for qualifying equipment as “Certified Equipment,” as defined under Rule 21 Section L.2.a, for which certification national standards have not been published for such piece of equipment.

SCE Type Testing Guidelines Version March 21, 2025 for Web.pdf

At any time, you can request technical information regarding SCE’s electric system around a potential interconnection site. To request this information, you need to provide details of the proposed site, the line and voltage level you are considering, and a non-refundable processing fee of $300.

The Rule 21 Optional Pre-Application Report Request, containing fee payment instructions, is available at the following link:

Rule 21 Optional Pre-Application Report Request

Upon receipt of a completed Pre-Application Report Request and the request fee, SCE will provide available system data. This typically includes:

• Total Capacity (in MWs) of substation bus
• Approximate circuit distance between the proposed site and the substation
• Relevant line section(s) peak line load estimate
• Number of protective devices and voltage regulating devices between the proposed site and the substation/area
• Whether or not three-phase power is available at the site
• Limiting conductor rating from proposed Point of Interconnection to distribution substation

For questions regarding the Pre-Application Report, please contact us at InterconnectionQA@sce.com.

SCE customers that operate generation systems for customer’s use only and do not export power for sales to SCE’s electric grid are referred to as “non-export” (or “non-exporting”) generators. Non-export projects include all generating facilities to be operated by, or for, a customer to serve part or all of its electric energy requirements that would otherwise be provided by SCE, including “distributed generation”, “cogeneration”, emergency, backup, and standby generation.

Backup Systems

“Backup systems” are non-exporting generators used by customers to serve part or all of their electrical needs during a power outage. These generators will normally be operated only when SCE’s electric service is not available or in an emergency.

Please visit our Backup Systems for more information about the various types of backup systems and the process to obtain interconnection.

While customers operating backup systems under either momentary parallel or isolated mode are not obligated to enter into an interconnection agreement with SCE, an interconnection application still needs to be completed to satisfy SCE’s notice requirements for operating such generating facility as per California Health and Safety Code Section 119085 (b).

Inadvertent Export

Certain non-exporting systems are optimally sized to meet the customers’ peak demand. These systems have generator controls to ensure export of electrical power to SCE’s electric system is minimized. When the load changes rapidly and the generator cannot ramp down quickly enough, the facility may need to export small amounts of power for a limited duration. The event of exporting uncompensated power for a duration exceeding two seconds but less than 60 seconds is referred to as Inadvertent Export. Please refer to Section M of Rule 21 regarding technical requirements regarding Inadvertent Export.

Application for Interconnection

You can now apply to interconnect a non-exporting project using our form 14-732 online!

All new non-exporting generation projects seeking interconnection service under Rule 21 are required to submit a Rule 21 application form online or by downloading the (Generating Facility Interconnection Application, PDF Form 14-732). The following contains a link to the application, with instructions on how to remit the applicable fee, and a list of documents required to be submitted with your application package:

• Application form for non-exporting generators: Generating Facility Interconnection Application, Form 14-732
• A single-line drawing
• Site/plot plan drawing
• Diagrams, manufacturer’s data, and written descriptions of the switching device or scheme proposed
• Diagrams, manufacturer’s data, and written descriptions of the backup switch, protective device, or any other control that will trip the generator if the transfer switch or scheme does not complete the transfer in one second or less
• Interconnection Request Fees. The application review requires a non-refundable fee of $800. Instructions on how to make this payment are included in the application form listed above

For a sample on acceptable single lines and site plans, please review this: Sample drawings

Once completed, please email electronic copies of your documents (items 1 through 6, above) to Rule21@sce.com, or mail your documents to:

Interconnection Process

Following the submittal of the application package and the interconnection request fee, an assigned engineer will perform a validation of the technical data provided. Once the application package is deemed complete and valid, a technical review will be performed to approve the proposed configuration and operation of your non-exporting system and to identify any necessary upgrades for interconnection of the project. After all technical reviews or studies are completed, you will receive an interconnection agreement that will establish the terms and conditions that your interconnection will be subject to.

Interconnection Agreement

Projects operating backup systems under either momentary parallel or isolated mode are not obligated to enter into an interconnection agreement with SCE. For all other non-exporting projects, please refer to Part 3 of the Rule 21 application form (Generating Facility Interconnection Application, Form 14-732) for a reference of the agreements that may apply to your project.

Generally speaking, “exporting projects” are those generating systems that are designed for the purpose of supplying unused power into SCE’s electric system for sale to SCE, a third party, or the market, or for delivery to another eligible customer or authorized entity.

Eligibility of Exporting Projects for Interconnection Under Rule 21

Exporting projects can only request interconnection service under Rule 21 if they intend to participate in an eligible energy program approved and under the jurisdiction of the CPUC (e.g., Schedule NEM, Schedule RES-BCT, or an eligible procurement program where 100% of the exported power is sold to SCE). For information about the procurement programs that qualify for interconnection under Rule 21, please refer to SCE’s Energy Procurement site.

Sales to 3rd Parties. If the project developer is intending to sell any portion of the exported energy or any capacity services from the project to a 3rd party (any entity other than SCE, including other utilities), or in the market, then the interconnection service must be obtained under a FERC jurisdictional tariff (such as SCE’s WDAT, or the CAISO tariff, depending on applicability).

Application for Interconnection

For information regarding the request for interconnection for new Solar Billing Plan projects, please visit the Solar Billing Plan webpage.

New non-NEM exporting generation projects seeking interconnection service under Rule 21 (including projects intending to participate in the Schedule RES-BCT) are required to submit an application form (Rule 21 Exporting Generator Interconnection Request, Form 14-918). The following contains a link to the application, with instructions on how to remit the applicable fee, and a list of documents required to be submitted with your application package:

• Application form: Rule 21 Exporting Generator Interconnection Request, Form 14-918
• A single-line drawing
• Site/plot plan drawing
• Proof of Site Exclusivity
• Diagrams, manufacturer’s data, and written descriptions of the generating facilities
• Interconnection request fees. The application review requires a non-refundable fee of $800. Instructions on how to make this payment are included in the application form available at the link above

Distribution Service
 

In addition, projects connecting to SCE’s distribution system through Rule 21 are required to obtain “Distribution Service” with SCE. “Distribution Service” allows the customer to be able to use SCE’s distribution system to “transport” their energy from the point of interconnection with SCE’s electric system to the CAISO system (where most power sales are expected to be delivered and settled in accordance with the CAISO market rules).

• Distribution Service Request Form (fillable)

For guidelines on providing documentation of Site Exclusivity, please review this Site Exclusivity Guidelines.

For a sample on acceptable single lines and site plans, please review this: Sample drawings.

Storage Project. Supplementary information is required in order to evaluate projects with energy storing capabilities. As part of your application, please provide the following additional technical data.

Once completed, please email electronic copies of your documents (items 1 through 6, above) to Rule21@sce.com, or alternatively, mail your documents to:

What Happens After Submitting your Application for Interconnection

Following the submittal of the application package and the review fee, an assigned engineer will perform a validation of the technical data provided. Once the application package is deemed complete and valid, the review/study track that is applicable to your project will begin (see Rule 21 Review/Study Tracks section below).

Additional Information

Please review the Information Available Prior to Requesting for Interconnection under Rule 21 section above for more information that can be helpful when submitting a request for interconnection.

Prior to obtaining interconnection, SCE performs technical reviews to identify how the project can be interconnected to SCE’s electric system in a safe and reliable manner while complying with all applicable standards and regulations. Under Rule 21, the technical review of projects requesting interconnection service can be done under the Fast Track Process or the Detailed Study Process. For information about these two tracks, please read the sections Fast Track Process under Rule 21 or the Detailed Study Processes under Rule 21 below.

When completing the application form, the customer can select, based on eligibility, the preferred track for reviewing the project.

Note: Non-exporting projects operating in parallel with SCE’s electric system (using application form 14-732) are evaluated only under the Fast Track Process. Only exporting projects (using application form 14-918) can select, based on eligibility, their desired review track.

The Fast Track Process is intended for projects that can be interconnected without system upgrades: it allows for a faster review of an interconnection request against a set of predefined screens to determine whether the project can interconnect without the need for detailed engineering studies or significant upgrades to SCE’s electric system.

The Fast Track review consists of an Initial Review and, if needed, a Supplemental Review. The Initial Review involves the evaluation of Screens A through M (described in Section G.1 of Rule 21).

The need for Supplemental Review will be determined based on the results of the Initial Review screens. Projects that successfully pass Initial Review screens will be allowed to interconnect without a Supplemental Review.

If needed, SCE can perform a Supplemental Review, which requires an additional nonrefundable fee of $2,500. The Supplemental Review consists of the application of Screens N through P (described in Section G.2 of Rule 21).

Projects that pass the Supplemental Review will be allowed to interconnect without further engineering studies. Failure to pass Fast Track evaluation (after the Initial Review and the Supplemental Review have been performed) means that the project needs further review (or study) before it can interconnect to SCE’s electric system. It does not mean that the project cannot be interconnected.

Fast Track Eligibility. Projects need to be “eligible” for the Fast Track review before the Initial Review and the Supplemental review are performed. Eligibility to request a Fast Track review means that the project can be evaluated under the Initial Review and the Supplemental Review screens, but eligibility does not guarantee that the project passes Fast Track.

Non-Exporting projects (using application form 14-732) and Net Energy Metered/Net Billing Tariff projects (using application form 14-957) are eligible for Fast Track evaluation regardless of the gross nameplate rating of the proposed generating facility. Exporting projects (using application form 14-918) are encouraged to review the Integration Capacity Analysis (ICA) for information relevant to their project. 
See also the Distribution Resources Plan External Portal (DRPEP): https://ltmdrpep.sce.com/drpep/

Typical Timelines for Fast Track Review Process. The Initial Review is normally completed within fifteen (15) business days after the application package is deemed complete and valid.

• Activities following Initial Review analysis:
  • If the project passes the Initial Review screens, and there are no identified upgrades required for interconnection, SCE will deliver a draft interconnection agreement within fifteen (15) business days following the Initial Review results.
  • If the project passes the Initial Review screens, but there are identified upgrades required for interconnection, SCE will deliver a cost estimate of such upgrades within fifteen (15) business days following the Initial Review results.
  • If the project does not pass the Initial Review screens, SCE may hold a meeting with the customer to determine the next steps and recommended options for the project, which may include conducting a Supplemental Review or moving the project to the Detailed Study Process.

If SCE and the customer agree to perform a Supplemental Review, the review is normally completed within twenty (20) business days after receipt of supplemental review fee.

• Activities following Supplemental Review analysis:
  • If the project passes the Supplemental Review screens, and there are no identified upgrades required for interconnection, SCE will deliver a draft interconnection agreement within fifteen (15) business days of providing the Supplemental Review results.
  • If the project passes the Supplemental Review screens, but there are identified upgrades required for interconnection, SCE will deliver a cost estimate of such upgrades within fifteen (15) business days following the Supplemental Review results.
  • If the project does not pass the Supplemental Review screens, SCE may hold a meeting with the customer to determine the next steps and recommended options for the project, which may include moving the project to the Detailed Study Process. Please review the Detailed Study Processes under Rule 21 section below for more information.

Interconnection Agreement. Following the receipt of a cost estimate for new facilities identified during the Initial Review or the Supplemental Review, the customer can request a Generator Interconnection Agreement within fifteen (15) business days. SCE will deliver a draft interconnection agreement within fifteen (15) business days of the customer’s request. At that point, SCE and the customer begin negotiations under the timelines provided in Section F.2.e of Rule 21.

Notes About Deliverability. All projects reviewed under the Fast Track Process are considered Energy Only (also referred to as Energy Only Deliverability Status, or EO). Energy Only projects do not qualify to provide Resource Adequacy benefits to Load Serving Entities (“Resource Adequacy” and “Load Serving Entities” are terms defined by the California Public Utilities Commission).

Projects that are not eligible for Fast Track evaluation, or that failed the Fast Track Process, can apply for a Detailed Study. A detailed study is an engineering study of a project that evaluates its impact to SCE’s electric system and identifies the facilities that are needed to accommodate the interconnection of the project.

There are three types of Detailed Studies: an Independent Study, a Distribution Group Study, and a Transmission Cluster Study. The specific Detailed Study applicable for a project is determined by Screen Q (which identifies if the project is electrically independent from other projects in the transmission system) and Screen R (which identifies if the project is electrically independent from other projects in SCE’s distribution system). Refer to Section G.3 of Rule 21 for a description and applicability of Screens Q and R.

• For full transparency related to the evaluation of Screen Q, SCE will make a determination of electrical independence for the CAISO Controlled Grid as set forth in Section 4.2 of Appendix DD of the CAISO Tariff: AppendixDD-GeneratorInterconnectionDeliverabilityAllocationProcedures-asof-Mar28-2023.pdf (caiso.com).
• If the project passes both Screen Q and Screen R, the project can proceed to the Independent Study Process (refer to section F.3.b of Rule 21 for a description of this process)
• If the projects passes Screen Q, but fails Screen R, the project can proceed to the Distribution Group Study Process (refer to section F.3.c of Rule 21 for a description of this process)
• If the project fails screen Q, the project is required to withdraw its application from the Rule 21 Process and proceed to the Transmission Cluster Study Process (refer to section F.3.d of Rule 21 for a description of this process). The project with then be processed for interconnection under SCE’s WDAT (please visit our WDAT page for more information).

Normally, for projects seeking to be evaluated under the Independent Study Process, SCE provides the results of the evaluation of Screens Q and R within twenty (20) business days following validation of an interconnection request and receipt of the appropriate study deposit set forth in Section E.3.a. For projects seeking to be evaluated under the Distribution Group Study Process, SCE provides the results of the evaluation of Screens Q and R within twenty (20) business days following the close of the Distribution Group Study application window.

Consistent with SCE’s expressed commitments through the 2024 CPUC’s Interconnection Discussion Forum, SCE makes available the attestation form linked below for generator inverter manufacturers to use to demonstrate to SCE a manufacturer’s derating of a project’s inverter from its Gross Nameplate Rating that may be submitted for purposes of calculating Rule 21 Detailed Study Deposit Fee.  

As of the publication of this notification, SCE will accept a completed attestation form (linked below) from a manufacturer to demonstrate an inverter derating from its Gross Nameplate Rating to a rating of 5MW or less, for a generating facility included in a previously submitted Customer Interconnection Request on or after March 1, 2024 to SCE. 

Upon satisfactory demonstration to SCE that the inverter has been derated to 5MW or less of its Gross Nameplate Rating, with the required information provided from the Manufacturer through use of the attestation form, SCE will accept a Detailed Study Deposit fee per that inverter’s appropriate re-rating as designated under Table E.1 in SCE’s Rule 21.

Customer understands that all other required applicable provisions of Rule 21 must also first be satisfied to demonstrate a completed Interconnection Request, which includes submission of the Detailed Study Deposit fee.

Should customers have any questions concerning the process for demonstration of Manufacturer inverter derating for the purposes addressed above, please contact SCE at InterconnectionQA@sce.com.

Customers may access form “Attestation for Demonstration of Derated Inverter for Purposes of Calculating Rule 21 Detailed Study Deposit Fee” at the following link: Attestation for Derated Inverter.pdf

Beginning March 1, 2024, SCE will utilize this methodology SCE's interim methodology for assessing contribution to RNUs.pptx as an interim process to assess whether a proposed Generating Facility is not reasonably anticipated to require or contribute to the need for Reliability Network Upgrades as part of the Screen Q assessment pursuant to Section G.3.a of SCE’s Rule 21 Tariff and as part of the electrical independence assessment pursuant to Section 5.5 of SCE’s WDAT Attachment I.

In accordance with SCE's Rule 21 generator interconnection procedures, SCE will open a Distribution Group Study (DGS) Application Window within the following schedule:

DGS Application Window Schedule

• DGS21 - Section E.2.c of SCE’s Rule 21 tariff states that there will normally be two Distribution Group Study Application windows annually. The first Distribution Group Study Application window will usually open on March 1 and close on March 31. The second Distribution Group Study Application window will usually open on September 1 and close on September 30. SCE’s Rule 21 also states that SCE, as the Distribution Provider, may change the Distribution Group Study Application window interval and opening or closing dates. Any changes are to be posted on the SCE’s website and if there is a conflict between the Distribution Group Study Application window interval and opening or closing dates posted on the Distribution Provider’s website and the dates identified in Rule 21, the dates posted on the Distribution Provider’s website shall apply. 

  As permitted under Rule 21 Section E.2.c, SCE hereby provides notice on February 1, 2025, that SCE is making the following revisions to the 2025 Distribution Group Study Application window because of abnormal circumstances leading to the delay in the resumption of the CAISO’s Queue Cluster 15: 

  • The Distribution Group Study Application window that would usually open on March 1, 2025, and close on March 31, 2025, will not occur.
  • SCE will have only one Distribution Group Study Application window in 2025, which will open on September 1, 2025, and close on September 30, 2025. 

  SCE will continue to accept Rule 21 Fast Track and Independent Study interconnection requests, without any changes or revisions to that process. 

Interconnection Requests to be studied under the Distribution Group Study Process shall either be (a) an Independent Study Process Interconnection Request that passed screen Q and failed Screen R for which the Applicant elects to continue to the next available Distribution Group Study, or (b) an Interconnection Request submitted during a Distribution Group Study Application window that passes Screen Q. Please refer to Rule 21 for a description of Screens R and Q Rule 21 Link.

New Interconnection Requests for the Independent Study Process will NOT be accepted during the Distribution Group Study application window dates listed above.

• Catalina Distribution Group Study Application Window, Opening Date: Monday, October 2, 2023. Closing Date: Tuesday, October 31, 2023.
  • Per Resolution E-5269, SCE’s Request for Rule 21 Site Exclusivity Deviation for Catalina Island’s Clean Energy All-Source Request for Offers was approved on August 10, 2023. Catalina interconnection requests sited at Middle Ranch are exempt from submitted site exclusivity documentation. For more information, view SCE’s Catalina Island All-Source RFO page.

On June 24, 2021, the CPUC confirmed Advice Letter 4461-E/E-A related to submitting Modifications to Rule 21 Requests.

A notification to SCE is required for certain modifications to a generating facility. Please refer to the Rule 21 tariff sections Ee. and F.2.a. (Table F.1) for additional information. The notification form is available here: Modification Notification

• Accelerate your project on the path to obtaining Permission to Operate. Providing sufficient documentation up-front can greatly reduce review and processing timelines.
  • Please refer to this checklist for more information to see if your project is eligible.
  • A presentation from 7/1/2020 is also available for your review.
• Pre-Approved Single Line Diagrams for projects selecting Protection Options 3 or 6 are now available for use. You may download these documents and attach them to your Interconnection Request submittal. If these do not accurately reflect your project, or you are using a different protection option, then you will need to provide your own Single Line Diagram with your Interconnection Request.
  • Protection Option 3 Single Line Diagram Template for Rule 21 Non-Export Energy Storage Less than 10kW
  • Protection Option 6 Single Line Diagram Template for Rule 21 Non-Export Energy Storage Less than 10kW

Installing a Rule 21 Non-Export Energy Storage system sized less than or equal to 10kW?

Accelerate your project on the path to obtaining Permission to Operate. Providing sufficient documentation up-front can greatly reduce review and processing timelines.

• Please refer to this checklist for more information to see if your project is eligible.
• A presentation from 7/1/2020 is also available for your review.

Pre-Approved Single Line Diagrams for projects selecting Protection Options 3 or 6 are now available for use. You may download these documents and attach them to your Interconnection Request submittal. If these do not accurately reflect your project, or you are using a different protection option, then you will need to provide your own Single Line Diagram with your Interconnection Request.

• Protection Option 3 Single Line Diagram Template for Rule 21 Non-Export Energy Storage Less than 10kW
• Protection Option 6 Single Line Diagram Template for Rule 21 Non-Export Energy Storage Less than 10kW

The following is a White Paper regarding workable options for interconnection customers to transfer from a Rule 21 Interconnection Request to a Wholesale Distribution Access Tariff (WDAT) Interconnection Agreement: White Paper

CRC Suspension for Microgrids