Urgent Alert

Wholesale Generation

Understanding wholesale interconnection agreements and processes

Wholesale interconnections

Developing a solar farm or non-solar generating facility that produces more than five megawatt (MW) of electricity requires careful planning. You must take additional steps when you’re interested in selling your generated power on the California Independent System Operator (CAISO) market through the PG&E distribution system. 


Get interconnection agreement process information

If you want to connect a self-generation system to the PG&E electric grid, you must obtain an interconnection agreement with PG&E. The Independent Study Process (ISP) and Cluster Study Process (CSP) enable you to apply for interconnecting your generating facility to a PG&E substation 12 kilovolt (kV) or 21 kV bus through a dedicated circuit, called a gen-tie, which you construct. The power you generate is typically redistributed through feeders at the substation, and then to customers through the transmission system.


Review the following interconnection information for your solar farm or generating facility


Slides to learn the required steps and processes

Get started with interconnecting your system

Review the application checklist and form instructions

Submit your application online


Plan your project site

As you plan your project, check out the Photovoltaic Renewable Auction Mechanism map, which shows the following important information:

  • PG&E circuit names
  • Voltage of the electric facility nearest to your project site
  • Loading information
  • Information to help you choose an appropriate location

Visit Solar Photovoltaic (PV) and Renewable Auction Mechanism (RAM) Program Map

ISP and CSP differences

Understanding how Independent Study Process (ISP) and Cluster Study Process (CSP) differ is important to the success of your project.

The ISP independently evaluates an interconnection request for a generating facility by performing a System Impact Study and a Facilities Impact Study. Both studies must be completed within 60 business days. The total ISP application process may take from six to 12 months, and you may apply at any time.


After you apply, you must pass a two-part Electrical Independence Test (EIT). In the first part, PG&E and CAISO evaluate the interconnection studies of earlier-queued generating facilities to which your facility is electrically related. To find out your potential for passing the EIT, check the public queue for active projects connecting to substations at your point of interconnection. Download PG&E Wholesale Distribution Queue (XLS).


If your project fails either part of the EIT, you may reapply during the next CSP Cluster window. You may also reapply under the ISP for a similar point of interconnection after waiting 12 months from your failure notification date.

The CSP evaluates a group of interconnection requests collectively. You may only apply for CSP during the application window. For more details, view Section 4.1 of Attachment I: Generation Interconnection Procedures (GIP) of the Wholesale Distribution Tariff.


Engineering analyses for CSP requests are conducted in two phases. Both phases study distribution and reliability network issues or upgrades required to mitigate thermal overloads and voltage violations. The phases also address short-circuit, stability and other potential reliability issues.


Before you begin the CSP process, contact your local city or county building or planning department to learn the requirements for your project. Find your local building department. Visit Permit Office Locator.

The costs of interconnecting your generating system to the PG&E electric grid depend on the following factors:

  • System size
  • Substation and circuit capability
  • Voltage considerations

The electric system nearest to your site might not have the capacity to receive the amount of electricity you propose to generate. As a result, you may be required to pay for upgrades to interconnection facilities, distribution systems and networks. After you and PG&E agree on the scope of your project, we conduct a study to identify the costs and schedules for any required upgrades.

We help you navigate the interconnection process and rules, from submitting your application to obtaining your Permission to Operate. After we receive your completed application package and applicable fees, you meet with members of our Generation Interconnection Services (GIS) team to discuss the scope of your project. During this meeting we:

  • Discuss the PG&E engineering team's initial assessment of the impact of and minimum requirements for establishing an electrical connection between your installation and our distribution system.
  • Set timelines for PG&E to study and fully assess the impact and requirements of your project.
  • Provide an overview of the study process and key project milestones.

Our GIS team is here to help you ensure a successful project and a safe, reliable interconnection to the grid. Email the team with your questions at wholesalegen@pge.com.

Guides and resources

PG&E transmission interconnection handbooks

Glossary and common questions

Wholesale Generation Interconnection Services - Frequently Asked Questions

90 KB

California Independent System Operator Corporation Fifth Replacement Electronic Tariff

75 KB

Pacific Gas and Electric Company Wholesale Distribution Tariff (WD Tariff) Glossary of Terms

41 KB

Additional resources for wholesale generation

Federal Energy Regulatory Commission (FERC)

Learn about the standards for connecting your project to the grid.

California Independent System Operator (CAISO)

Get more information for new projects.

Contact us

If you have additional questions, contact Generation Interconnection Services (GIS) at wholesalegen@pge.com.