Assumptions for the 2026-2027 TPP
The Integrated Resource Planning (IRP) process develops a resource portfolio(s) annually as a key input to the California Independent System Operator's (CAISO) Transmission Planning Process (TPP) base case studies, which includes a reliability base case portfolio and a policy-driven base case portfolio. The California Public Utilities Commission (CPUC) may also transmit additional resource portfolios as inputs for sensitivity studies that test the implications of various policy futures. This page contains documentation relevant to the development and mapping of resource portfolios for the 2026-2027 TPP.
Transmission Planning Process Ruling and Ruling Development Materials
- 2026-2027 Transmission Planning Process Portfolio Ruling, 9/30/2025
- 2026-2027 Transmission Planning Process RESOLVE Analysis Slide Deck, 9/30/2025
- 2026-2027 Transmission Planning Process RESOLVE Package analysis, 10/6/2025 Note: These zip files are big, it is advised to download and open locally
- Raw RESOLVE Outputs
- Unprocessed RESOLVE outputs for Least-Cost Comparsion Case (TPP_Lease_Cost). Proposed Base Case (TPP_AB1373_Delayed_OSW). Proposed Sensitivity Case (TPP_Limited_Wind), GHG Reductions to 25 MMT(TPP_25MMT), DCPP Extension (TPP_Limited_Wind)
- RESOLVE Code Base and Inputs
- Code base and template Scenario Tool and Results Viewer, and inputs used for RESOLVE modeling
- RESOLVE Upstream Data Workbooks and Public Case Results Viewers
- Workbooks upstream of the RESOLVE Scenario Tool, Baseline Resources and Transmission Workbook, and Results Viewer for Least-Cost Comparison Case, Proposed Base Case, Proposed Sensitivity Case, GHG Reductions to 25 MMT, DCPP Extension
- Raw RESOLVE Outputs
- Updated Framework for Portfolio Selection, 9/30/2025
- Red-lined Framework for Portfolio Selection, 9/30/2025
Methodology for Resource-to-Busbar Mapping
The busbar mapping methodology states guiding principles, establishes mapping criteria, and outlines the iterative inter-agency mapping process.
Webinar - 11/12/2025 - IRP Webinar on the Proposed 2026-27 Transmission Planning Process Portfolios and Preliminary Busbar Mapping Results
- Objectives
- Familiarize stakeholders with proposed portfolios and busbar mapping process.
- Review the preliminary mapping results for the proposed base case portfolio.
- Provide an opportunity for stakeholders to ask clarifying questions about busbar mapping process and preliminary mapping results.
- Noticing Document (contains the webinar link)
Webinar – 08/19/2025 – IRP Webinar on Potential Updates to the Busbar Mapping Methodology
- Objectives
- Provide an overview of the busbar mapping process and its role in the transmission planning process.
- Present updated datasets from the CEC for use in the mapping criteria.
- Familiarize stakeholders with the potential updates to the criteria and the criteria alignment thresholds.
- Give opportunity to stakeholders to ask questions and provide comments on the busbar mapping methodology and the proposed criteria updates.
- Request stakeholders’ informal written feedback to be incorporated in the final updated methodology.