Determine what a California customer installing a non-exporting standby generator with an automatic transfer switch actually owes their utility under Rule 21, versus a full interconnection application

Steps

1. Confirm California's Electric Rule 21 (cpuc.ca.gov/Rule21) governs generating-facility interconnection statewide, with specific provisions distinguishing 'non-export'/'backup' systems (serving only the customer's own load during an outage) from exporting distributed generation
2. Note that under SCE's stated practice, customers operating backup systems in isolated or momentary-parallel mode aren't required to sign a full interconnection agreement but still must complete an interconnection application to satisfy the utility's notice requirements
3. Confirm the transfer switch itself must prevent inadvertent parallel operation with the grid (break-before-make) — SDG&E's public guidance describes a double-pole double-throw switch as the standard mechanism, with utility approval allowing the transfer switch to substitute for some protective-relay requirements otherwise required for parallel operation
4. Check the specific California IOU's (PG&E, SCE, or SDG&E) current Rule 21 non-export generator form/tariff page directly, since exact notification paperwork differs by utility even under the shared statewide Rule 21 framework