Transmission Development

Background

The CPUC provides key inputs to the Transmission Planning Process (TPP) conducted annually by the California Independent System Operator. This is done to ensure that TPP transmission planning aligns with the state's energy policies and objectives, with a focus on renewable energy integration, grid reliability, and cost efficiency.

CPUC-CEC-CAISO Memorandum of Understanding – December 2022 

This document guides the collaborative effort among the three entities through each TPP cycle: the CAISO conducts transmission planning based upon forward-looking resource portfolios developed by the CPUC and demand forecasts developed by the CEC.

CPUC Portfolios for CAISO TPP

Mapping of Resources-to-Busbars

The busbar mapping methodology states guiding principles, establishes mapping criteria, and outlines the iterative inter-agency mapping process.

Transmission Planning Process: Ruling and Ruling Development Materials

2025-2026 TPP Mapping Ruling, 10/30/2024 

2025-2026 Transmission Planning Process ruling, 9/12/2024  

2025-2026 Transmission Planning Process RESOLVE Analysis, 9/12/2024 

2025-2026 Transmission Planning Process RESOLVE Package analysis, 9/12/2024  

2025-2026 TPP Ruling Cluster Interconnection Limits, 10/10/2024  

2025-2026 TPP Build Base Adjustment for SERVM analysis workbook, 1/9/2025 

2025-2026 Resource Cost & Build workbook, 1/9/2025

CPUC Decision Transmitting Electricity Resource Portfolios to the CAISO for the 2025-2026 TPP

 

Proposed Decision Transmitting Electricity Resource Portfolios to the California Independent System Operator for 2025-2026 Transmission Planning Process, 1/10/2025  

Fact Sheet on 2025-26 TPP Proposed Decision, 1/15/2025  

Presentation summarizing updated RESOLVE and SERVM Analysis, 1/10/2025  

Proposed Decision Modeling Assumption Report for the 2025-2026 TPP, 1/15/2025    

Busbar Mapping for the Proposed Decision  

Full Dashboard for the PD 25-26 TPP Base Case, 1/10/2025 

This workbook is ~30 MB and includes a summary of the initial mapping results as well as the full analysis, including the calculations, equations, and data used to conduct the mapping and assess the criteria alignment.  

Compact Dashboard for the PD 25-26 TPP Base Case, 1/10/2025  

This version of the dashboard is 7 MB and is the smaller, compact version of the mapping results.  It includes only the results (fixed numbers) and not the equations, calculations, and supporting reference data that is used to conduct the busbar mapping analysis. 

Full Dashboard for the PD 25-26 LLT Sensitivity, 1/15/2025  

The workbook is ~30 MB and includes a summary of the initial mapping results as well as the full analysis, including the calculations, equations, and data used to conduct the mapping and assess the criteria alignment.   

Supplemental Workbooks for PD Busbar Mapping:

Updated Baseline Reconciliation and In-development resources, 1/10/2025  

Updated Commercial Interest analysis from CAISO's interconnection queue, 1/10/2025  

Initial Mapping Results for the Proposed Base Case 

The Initial Busbar Mapping Dashboard for the Base Case summarizes the initial mapping results, the mapped resources alignment with the busbar criteria, and the analysis used to assess that alignment.

Full Dashboard – Initial Mapping for the 25-26 TPP Base Case (11/1/2024) 

Corrected Full Dashboard -Initial Mapping Base Case (1/10/2025)

Staff fixed some calculations error in the initial mapping analysis.  

This workbook is ~33 MB and includes a summary of the initial mapping results as well as the full analysis, including the calculations, equations, and data used to conduct the mapping and assess the criteria alignment.

Compact Dashboard – Initial Mapping for the 25-26 TPP Base Case (11/1/2024)

Corrected Compacted Dashboard - Initial Mapping Base Case (1/10/2025) 

Staff fixed some calculations errors in the initial mapping analysis   

This version of the dashboard is ~5 MB and is the smaller, compact version of the mapping results. It includes only the results (fixed numbers) and not the equations, calculations, and supporting reference data that is used to conduct the busbar mapping analysis. 

Supplemental data workbooks for initial mapping effort. 

Baseline Reconciliation and In-development resources (11/1/2024) 

Land-use and Environmental Screens data (11/1/2024) 

Commercial Interest analysis from CAISO’s interconnection queue (11/1/2024) 

Commercial Interest analysis from Cluster 15 applications (11/1/2024)

Portfolios and Modeling Assumptions for Previous TPP Cycles  

Workshops and Webinars

Webinar – 11/05/2024 - IRP Webinar on the Proposed 2025-26 Transmission Planning Process Portfolios and Draft Busbar Mapping Results: 

Webinar – 12/08/2023 - IRP Webinar on Busbar Mapping Results for the Proposed 2024-25 TPP Portfolios:

Workshop – 10/20/2023 - Ruling Proposing 2023 Preferred System Plan and 2024-2025 Transmission Planning Process Portfolios:  

Webinar– 07/18/2023 - Busbar Mapping Methodology Updates:  

Transmission and Interconnection Delivery

Effective delivery of transmission and interconnection projects is crucial for California to meet its clean energy objectives. Several initiatives and legislative measures have been established to oversee and facilitate the development of transmission infrastructure: 

  • SB 319: California Senate Bill 319 mandates the California Public Utilities Commission (CPUC), in consultation with California balancing authorities, to submit biennial reports to the Legislature detailing the status of electrical transmission projects. It also requires the CPUC, the California Energy Commission, and the California Independent System Operator, on or before July 1, 2025, to jointly develop an electrical transmission infrastructure development guidebook that describes the state’s electrical transmission infrastructure planning and permitting processes.  
  • Transmission Development Forum (TDF): The TDF is a biannual forum hosted by CAISO in which transmission owners update stakeholders on the status of in-development CAISO-approved transmission projects and network upgrades. The TDF provides valuable information on emerging issues impacting project development and checks that transmission development is aligned with the TPP and state energy policies. 
  • SB 1174: California Senate Bill 1174 requires investor-owned utilities to report information about their transmission facility and system network upgrades that are currently in development, and the in-development renewable and storage resources that depend on these transmission projects. SB 1174 data is used to identify the magnitudes of, and primary reasons for, transmission delays, and to identify specific delayed transmission projects that have the largest impact on in-development resources. The latest SB1174 transmission system assessment can be found in the latest annual Renewable Portfolio Standards (RPS) report to the legislature.  
  • AB 3264: Assembly Bill 3264 section 913.10 of the Public Utilities Code, which requires a study with findings and recommendations for “reduc[ing] the cost to ratepayers of expanding the state’s electrical transmission grid as necessary to achieve the state’s goals, to meet the state’s requirements, and to reduce the emissions of greenhouse gases.” The study is led by the FERC Cost Recovery Section with close coordination with the IRP team.  

The CPUC also tracks and analyzes transmission and interconnection development to ensure the timely completion of infrastructure necessary to meet the state's clean energy goals. This includes participation in the CEC’s development of the AB525 Offshore Wind Strategic Plan, the SB319 Guidebook on California’s transmission system), and the SB1174 Assessment of Transmission System Delays).

 

 

 
 
 
 
 
 
 
 
 
 
 
 

 

 

 

 

 

 

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