MISO said last week it will file with FERC a proposal to create two separate but identical cost-allocation designs for its Midwest and South sub-regions that rely on a 100% postage stamp rate to load.

The proposal, to be filed in mid-December, will split the costs of its long-range transmission planning effort between the two regions.

Jeremiah Doner, MISO’s director of economic and policy planning, said Thursday that discussion of possibly sunsetting the bifurcated allocation approach after a few years or when the RTO approves a transmission project that strengthens the link between the two regions. MISO has said it hopes to use a footprint-wide cost allocation within a few years. (See MISO Hopes Bifurcated MVP Cost Allocation Will be Temporary.)

“One of the drivers for the cost-allocation approach is the limited transfer capability between the regions,” Doner told stakeholders during a Regional Expansion Criteria and Benefits Working Group (RECBWG) meeting.

Staff said they will commission a Brattle Group study on the footprint’s distribution of project benefits in the filing to prove that long-range project benefits are confined to regions. The RTO committed to conducting a similar study in 2026 and every three years thereafter to analyze benefits distribution.

General Counsel Timothy Caister said MISO plans to study projects that increase flows between the Midwest and South as part of the long-range plan’s later stages. He said the RTO may consider a different cost-allocation approach for those cross-regional projects.

MISO is studying the Midwest’s transmission needs before it begins analyzing the South’s needs. Caister also reminded stakeholders that MISO must incorporate any final rules from FERC’s advanced notice of proposed rulemaking, which is aimed at improving transmission planning and cost allocation.

Some stakeholders remain apprehensive about dividing regional transmission costs based on location.

Clean Grid Alliance’s Natalie McIntire asked what MISO would do if it found its proposed Midwest long-range projects are found to have footprint-wide benefits. She asked whether that might change the cost-allocation approach.

“To the extent that the study does not meet the hypothesis, we’ll be back here at the RECBWG,” Caister said.

“I really think it’s important that MISO design what’s best for the grid instead of working around arbitrary boundaries,” Sustainable FERC Project attorney Lauren Azar said.