Greater transmission connectivity across the Midwest and Great Plains could improve system reliability and resilience, expand access to lower-cost generation, increase transfer capability, and make more effective use of existing and planned infrastructure. Yet delivering tangible benefits to ratepayers requires more robust planning processes that can rigorously evaluate alternative solutions and advance cost-effective projects. The Midcontinent Independent System Operator (MISO) and Southwest Power Pool (SPP) have made progress toward this goal, moving beyond largely independent regional planning processes to undertake coordinated interregional studies. Over the past two years, MISO and SPP have undertaken a robust 2024-2025 Coordinated System Plan (CSP) focused on the southern portion of their shared boundary, or “seam,” spanning Oklahoma, Arkansas, northeastern Texas, and Louisiana.

Beginning in late 2026, MISO and SPP will scope the 2026 CSP, creating an opportunity to apply lessons from the 2024-2025 CSP and ongoing reforms to regional planning frameworks. To inform this effort, this report examines the RTOs’ regional transmission expansion plans, emerging system needs across their shared seam, and lessons from recent interregional planning efforts and offers recommendations to inform the 2026 CSP scoping process. Key findings include:

• MISO and SPP have invested in regional large-scale, high-capacity transmission systems that are geographically proximate.
• MISO and SPP have a unique opportunity to evaluate high-capacity interregional transmission solutions.
• MISO and SPP can apply Order No. 1920 regional planning improvements interregionnally.

Download the report below to learn more.