The ISO is developing an opportunity for developers to deliver generation to California without increasing the Transmission Access Charge (TAC) and without picking the winner by selecting a project in the Transmission Planning Process (TPP). The ISO intends to implement the Subscriber Participating Transmission Owner model as a win-win arrangement versus trying to extract value from those paying for the line for the benefit of the ISO’s existing ratepayers. This model allows the potential off takers/California load serving entities to make their own economic decisions with respect to which out-of-state generation projects to contract with, while the ISO would continue to exercise its existing tariff authority and utilize its supporting software systems to implement a new protocol.
Outcome Statement:
Approved by FERC in 2024, the Subscriber Participating Transmission Owner initiative allows transmission developers outside the CAISO’s balancing area footprint to finance transmission infrastructure and join the balancing area. This project made the process changes needed to make the model a reality, including adding the Subscriber PTO model to CAISO’s Transmission Planning Process, making updates that provide deliverability to the Subscriber, and establishing the necessary payment mechanisms. The project’s success has been demonstrated by operation of the first Subscriber PTO transmission project, SunZia, in mid-2026.
| Proposal Development | Decision | Implementation | Completed/Closed |
|---|---|---|---|
|
Jun 22, 2023 Final proposal posted
Aug 8, 2023 Revised draft tariff language posted |
Jul 20, 2023 Board of Governors approval
|
Summer 2026
Implementation milestones
|
Completed |