MISO’s Board of Directors unanimously approved Long Range Transmission Plan Tranche 2.1 in December 2024, authorizing $21.8 billion across 24 projects and 323 facilities spanning 3,631 miles through nine Midwest states. The backbone is a 765 kV high-voltage network targeting in-service dates from 2032 to 2034. MISO modeled a benefit-to-cost ratio of 1.8-3.5x, with projected net benefits of up to $72 billion over 20 years.
Tranche 2.1 follows MISO’s 2022 Tranche 1 approval of $10.3 billion in projects, which is still working through development. The combined two-tranche commitment represents the largest regional transmission investment in US history and reflects the underlying driver: the Midwest generation fleet is retiring coal capacity while adding wind and solar at the same time, creating transmission bottlenecks that are stranding clean energy in the wrong places and raising reliability risks. The 765 kV backbone is sized for decades of flow, not the current generation mix.
For investors, the MISO approval is a multi-year capital deployment event. The 24 projects flow through incumbent transmission owners, who earn regulated returns on construction capital. The developers whose projects have been waiting behind the transmission bottleneck, particularly in the MISO North and South regions, gain interconnection paths that did not previously exist on a reliable timeline. The practical constraint, as with all large transmission projects in the US, is permitting and right-of-way: MISO approval is the beginning of the process, not the end.