Backup Systems

“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).

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.