The Guidebook is intended to help a person or project team interconnect one or more electricity generators to the local electric utility grid in California under California Rule 21. Rule 21 applies only to the three electric utilities in California that are under jurisdiction of the California Public Utilities Commission: Pacific Gas and Electric, Southern California Edison, and San Diego Gas and Electric.
The Guidebook is written as an aid to interconnection in these utility areas.
It may also be useful for interconnection in some municipal utility areas
with interconnection rules resembling Rule 21, principally Riverside,
Sacramento Municipal Utility District, and the Los Angeles Department of
Water and Power.