Backup Systems

A generator that uses a “make-before-break” transfer scheme (also known as “closed transition”) where the generator is in parallel with SCE’s electric system for one second or less is said to be operating under a momentary parallel mode.

You are not required to obtain an interconnection agreement with SCE in order to install or operate systems operating in momentary parallel mode. However, the proposed make-before-break transfer scheme generator equipment packages (i.e., automatic transfer switch) must be reviewed and approved by SCE prior to operation to ensure compliance with the Rule 21 technical requirements and SCE’s Electric Service Requirements (“ESR”) manual.

Application for Interconnection

Before the design of the backup generator is finalized, the interconnection customer must submit a complete interconnection application package in accordance with SCE’s Rule 21. The following documents must be completed and submitted to us:

• Rule 21 Application Form for Non-Exporting Generators (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 in the event that 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.

You may now apply to interconnect a backup system using our form 14-732 online!

You may also, email electronic copies of your documents (items 1 through 5, above) to Rule21@sce.com, or alternatively, mail your documents to:

Interconnection Process

Following the submittal of the application package and review fee, an assigned engineer will perform a validation of the technical data provided with the application package. Once the application package is deemed complete and valid, a technical review will be completed to approve the proposed configuration and operation of your backup system. During this technical review, you will be required to demonstrate via a commissioning test that your generator complies with Rule 21 tariff requirements for backup operation under momentary parallel. Once all technical reviews and inspections are completed, you will receive a notification authorizing the operation of your backup system.

Additional Information

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

Please visit Rule 21 page to learn more about Rule 21 and the technical requirements that may apply to your project.

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.

A generator that uses an automatic or manual transfer scheme where part or all of a customer’s usage is transferred between the SCE’s distribution system and the generator, but is never in parallel with the SCE’s electric system is said to be operating in isolated mode. In isolated mode, a generator uses a “break-before-make” transfer scheme (also known as “open transition”).

You are not required to obtain an interconnection agreement with SCE in order to install or operate systems operating in isolated mode. However, the proposed transfer switch or operating scheme specifically designed and engineered for such operation must be reviewed and approved by SCE prior to operation to ensure that the generator will never operate in parallel with SCE’s electric system.

Application for Interconnection

Before you complete the design of your backup generator, you must submit a complete interconnection application package to satisfy SCE’s notice requirements for operating an isolated backup generator as per California Health and Safety Code Section 119085(b). The following documents must be completed and submitted to us:

• Rule 21 Application Form for Non-Exporting Generators (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

No Review Fees. Generators operating under an isolated mode do not require any application fees.

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

You may now apply to interconnect a backup system using our form 14-732 online!

You may also, email electronic copies of your documents (items 1 through 4, above) to Rule21@sce.com, or alternatively, mail your documents to:

Interconnection Process

Following the submittal of the application package, an assigned engineer will perform a review of the technical data provided with the application. The assigned engineer will work with the customer to complete the technical review and approve the proposed configuration and operation of your emergency backup system. To demonstrate that your generator complies with Rule 21 requirements for backup operation under isolated mode, a site inspection may be necessary. Once all the technical reviews, and inspections are completed, you will receive a notification authorizing the operation of your backup system.

Additional Information

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

Please visit Rule 21 page to learn more about Rule 21 and the technical requirements that may apply to your project.

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.