Rule 21 is the California Public Utilities Commission tariff that governs how generators and storage, including bidirectional EV chargers, interconnect to the distribution systems of the state’s investor-owned utilities. It sets the technical requirements, review process, and timelines for exporting power to the grid.
Why it comes up
- Any EV charger that exports energy is treated as a generating facility and must go through Rule 21 review, which is one of the barriers the California Energy Commission names for bidirectional charging.
- The process is slower and more complex than a standard charger installation, which only draws power.
Why it matters for parking
A facility planning vehicle-to-grid or a battery energy storage system should budget for a Rule 21 interconnection study as a schedule item, not a formality. One application can cover a whole garage.