Electric Rule 21: Distributed Generation Interconnection Rules

Electric Rule 21 is a set of rules governing how energy technologies such as bioenergy, geothermal, solar and wind, including advanced energy technologies, may interconnect to the electric distribution systems of the state’s investor owned utilities – Southern California Edison, Pacific Gas and Electric, San Diego Gas &Electric, Bear Valley Electric, Liberty Utilities and PacifiCorp Power. These advanced technologies include Energy Storage and Distributed Generation such as roof-top solar. The Rule 21 Tariff provides customers with a process to interconnect if they wish to install generating or storage facilities on their premises with access to the electric grid while protecting the safety and reliability of the distribution and transmission systems.



Since its establishment in 1982, Rule 21 has been the subject of three major proceedings. In November of 2000, the CPUC issued a Decision to establish a more standardized and transparent engineering analysis for the interconnection of distributed generation, adopting an “Initial Review” screening process to help identify if the generating facility is within technical limits so as to not cause electrical disruptions on the grid.

In September 2011, the CPUC opened Rulemaking (R.11-09-011) to review and revise Rule 21 to “ensure that the interconnection process is timely, non-discriminatory, cost-effective, and transparent.” More information about this proceeding and ORA’s position can be found here.

On July 21, 2017, the CPUC issued a Rulemaking (R.17-07-007) to streamline interconnection of distributed energy resources and to make improvements to Rule 21. More information on this most recent proceeding can be found here.