“Backup systems” are 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. Most backup systems are designed to operate independently from SCE’s electric system by using an automatic transfer switch to sense the loss of power from SCE and initiate power use from this generator. Once SCE’s electric service is restored, the generator’s automatic transfer switch will shift the customer’s usage back to SCE and will signal the backup generator to shut-off.
Typically backup generators will use diesel, natural gas, or liquid propane to operate.
Generators operating as a backup system will do so either under a momentary parallel mode or isolated mode:
- Momentary Parallel operation mode. A backup generator that interconnects and operates on a momentary parallel basis with SCE’s electric system for a duration of one (1) second or less through transfer switches or operating schemes specifically designed and engineered for such operation.
- Isolated operation mode. A backup generator that will be isolated and prevented from becoming interconnected with SCE’s electric system through a transfer switch or operating scheme specifically designed and engineered for such operation.
While customers operating backup systems under either momentary parallel or isolated mode are not obligated to enter into an interconnection agreement with SCE, an application for interconnection 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).
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:
| Grid Interconnection & Contract Development Southern California Edison 2244 Walnut Grove Ave Rosemead, CA 91770 |
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:
| Grid Interconnection & Contract Development Southern California Edison 2244 Walnut Grove Ave Rosemead, CA 91770 |
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.
DISCLAIMER: The guidelines in this section are provided with the intent to help SCE’s customers understand SCE’s Interconnection Procedures. However, in the case of discrepancies with SCE’s rules, such tariffs and regulations will prevail.