The California ISO 2026-2027 transmission planning cycle involves key stakeholder activities from 2026 through early 2027. Each year, the ISO conducts its transmission planning process to identify potential system limitations as well as opportunities for system reinforcements that improve reliability and efficiency. The transmission planning process core product is the ISO Transmission Plan, which provides an evaluation of the ISO control grid, examines conventional grid reliability requirements and projects, summarizes key collaborative activities and provides details on key study areas and associated findings.
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Dec 30, 2025 30-day Comment period begin - study plan development
Feb 19, 2026* Draft study plan posting Feb 24, 2026* Meeting Mar 10, 2026* Comments due Mar 31, 2026* Final study plan posting Aug 14, 2026* Post preliminary reliability study results and mitigation solutions Aug 28, 2026* Post scenario base cases Sep 23, 2026* Meeting (day 1) Sep 24, 2026* Meeting (day 2) Oct 08, 2026* Comments due Oct 30, 2026* Post final reliability study results Nov 16, 2026* Post preliminary assessment of policy and economic planning studies Nov 18, 2026* Meeting Dec 04, 2026* Comments due Mar 31, 2027* Draft transmission plan posting April 7, 2027* Meeting May, 2027* Board of Governors May 31, 2027* Final board-approved transmission plan posting |
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Stakeholder comment period for 2026-2027 unified planning assumptions and study plan is Dec 30, 2025 through Jan 30, 2026. See the notice for more information.
Link to Dec 30, Notice 01/07/2026
Letter - Data Request and Invitation to 2026-2027 Transmission Planning Process - Dec 30, 2025 01/07/2026
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