MISO and SPP said they will study more than 30 project suggestions — some estimated to cost more than $1 billion — in a four-state area in their pursuit of major, regionally cost-shared transmission projects.
The grid operators said they received 46 stakeholder-originated ideas for projects along their seam in Arkansas, Louisiana, Oklahoma and Texas. The two RTOs have culled the projects to 32 proposals and said they will test their potential and may build business cases for some under their coordinated system plan. (See MISO, SPP Still on Hunt for Joint Transmission Under CSP.) MISO and SPP ruled out most of the eliminated projects for focusing on local — not interregional — issues.
The 32 project contenders are concentrated along:
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- Northeastern Oklahoma to northern Arkansas, where stakeholders submitted multiple greenfield 765-, 500- and 345-kV project ideas alongside reconductoring and additional transformer suggestions.
- Eastern Oklahoma to central Arkansas, which drew 500- and 345-kV line ideas.
- The Oklahoma-Texas eastern border to northeastern Louisiana garnered 765- and 345-kV proposals with ideas for new transformers, substations and transformer upgrade submissions.
- The Oklahoma-Texas eastern border to southwestern Arkansas, which could host new 500- and 345-kV lines and reconductoring, electrical reactor and double-circuit work.
- Eastern Texas to central Louisiana, where stakeholders recommended 500-kV work.
Ashleigh Moore, of MISO’s interregional planning division, said MISO and SPP will analyze the candidates’ performance in terms of adjusted production cost savings, mitigation of reliability issues and transfer capability improvements.
At the Oct. 24 MISO-SPP Interregional Planning Stakeholder Advisory Committee (IPSAC), MISO and SPP said they would have draft recommendations ready to share by the Dec. 12 IPSAC meeting. Staff said they will have more data, maps, and benefit estimates and adjusted production cost savings estimates then.
The projects’ price estimates range from $54 million to nearly $4 billion for one HVDC idea in northeastern Oklahoma and northern Arkansas. Eight projects on the list are estimated to cost more than $1 billion.
Moore said MISO and SPP are encouraged by the “valuable project ideas” from their stakeholders and that they were glad to see some of the projects zeroing in on key reliability paths between the RTOs. She said MISO and SPP will narrow the 32 “good ideas” to “high-performing, feasible and cost-effective” projects.
MISO’s Jon George said the projects may culminate in a portfolio of interregional projects, with benefit-to-cost ratios calculated among a group of projects rather than individually.
The RTOs still are working on their 15-year modeling to build studies on and said it would be complete in November.
MISO and SPP said they may use the seven transmission benefits established in FERC Order 1920 to develop business cases for projects. If the two find beneficial projects, or a portfolio of projects, they would need to propose an interregional cost allocation plan for FERC approval. The two RTOs said cost sharing could be tackled in late 2026.
Southern Renewable Energy Association Executive Director Simon Mahan said while MISO and SPP’s coordinated system plan studies in the past have been disappointing, this fresh list of project candidates seems promising.
“I think this is going to be getting us closer,” Mahan said. He said some of the projects appear to be able to help outages that occurred earlier in 2025 in the Shreveport, La., area and previous voltage problems in northwestern Arkansas and southwestern Missouri during Winter Storm Elliot in late 2022.
MISO and SPP have never recommended a major, interregional cost-shared transmission project through their coordinated system plan study, despite five previous attempts. The RTOs’ $1.6 billion Joint Targeted Interconnection Queue transmission portfolio is to be paid for by interconnecting generation and is considered separate from their coordinated system plans.
Mahan said some of the project ideas appear to potentially boost transmission capacity to allow more MISO Midwest-South power flows. He asked if MISO would examine some projects for that value.
Moore said while MISO and SPP are time-constrained for this study, MISO plans to keep the list of projects ideas to draw on in future planning studies.
MISO-SPP TMEPS in the Works
Meanwhile, work will continue into 2026 on MISO and SPP rules to create a smaller, congestion-relieving interregional transmission project category.
MISO and SPP are in the process of drafting rules for a targeted market efficiency project (TMEP) type, modeled after the MISO and PJM existing interregional study that produces less expensive transmission projects that can be built quickly.
SPP Senior Interregional Strategist Jill Ponder said MISO and SPP plan to file new language to their joint operating agreement and an RTO-to-RTO cost allocation for TMEPs in either the first or second quarter of 2026.
Speaking at MISO’s August Planning Advisory Committee meeting, Moore said MISO and SPP view TMEPs as a “bridge in our planning toolbox” and said any MISO-SPP TMEPs will not “undermine or duplicate planning efforts.”
MISO stakeholders in written feedback expressed a concern that TMEP planning could risk overlapping with the existing MISO and SPP regional and interregional studies.
So far, the MISO and SPP draft TMEP study process would rely on historical data to weed out congestion on the seam and advance small transmission projects that can be built quickly to alleviate it. Moore said TMEPs are intended to supplement — not replace — long-term planning initiatives like MISO’s long-range transmission planning and the MISO and SPP Joint Targeted Interconnection Queue. Moore said TMEPs would solve only issues not expected to be “substantially alleviated by system changes” on a five-year horizon, including known upgrades.
Moore also said the two RTOs are striving to make the new process as transparent as possible. She said the RTOs will post historical congestion data annually and will commit to documenting the screening of potential projects in study reports “to explain why some move forward while others don’t.”