MISO said it likely will create interconnection reliability requirements and explore new rules that could bring large customers online in stages, as capacity becomes available, to get a handle on large loads eyeing MISO locales.

MISO anticipates drafting “a set of guidelines and requirements” for large loads that wish to interconnect to maintain reliability. The RTO made the announcement at a Jan. 30 stakeholder workshop dedicated to large load preparation.

Executive Director of Markets and Grid Research DL Oates said MISO’s stakeholders view the grid operator as having a role in providing reliability interconnection guidelines.

Manager of Strategic Assessments Beibei Li said MISO can draw on its existing inverter-based resource requirements for ideas. She said MISO would need loads’ telemetry to maintain system reliability and stability and that it would use their data in modeling and planning.

MISO plans to introduce the topic to the Planning Advisory Committee for discussion in the next few months with the goal of working on a ruleset sometime around mid-2026.

Oates said MISO “is hesitant to provide exact dates” on when it could file tariff changes with FERC on the reliability requirements.

Oates said for years MISO has operated with an approximate 120-GW peak demand across its 45 million customers. He said by 2030, MISO could add anywhere from the “low 10s to the high 20s” of gigawatts.

“So, something like 15% of growth with a fair bit of uncertainty around that,” he said.

Oates said the new load coming MISO’s way is unlike anything MISO has seen: “It is, to put it very simply, very big.”

Jordan Bakke, MISO’s director of strategic insights and assessments, said there’s sizable reliability risk that large load customers could introduce.

“We expect large loads to behave in a way that’s hard to predict,” Bakke said. He said large loads have “unique disturbance behaviors,” including frequency sensitivity, low fault current and oscillations. He also said these loads have “unknown and varied ride-through performance” alongside complex protection schemes that make for complex stability assessments.

Minnesota Power’s Tom Butz said MISO appeared to have a great number of concerns over stability that come with large load customers. He asked if MISO has existing study processes to test how large loads specifically strain the system.

“MISO itself has very limited study as it relates to large load interconnection,” Bakke said.

Vice President of Operations Renuka Chatterjee said MISO will be “looking at some AI tools” for study assistance and promised “more to come.”

‘Speed to Partial Power’

MISO is toying with the idea of providing what it calls “speed to partial power.”

MISO Director of Expansion Planning Jeanna Furnish said large loads can make it online in a little more than a year, while generation takes about four years and transmission typically takes about seven to 10 years. She said load could be left trying to withdraw before generation or transmission arrive on scene.

Furnish said MISO’s ongoing work to create zero-injection generator interconnection agreements can help speed up generation projects that plan to send their output solely to their dedicated loads, not the greater system. (See Questions Abound over MISO Idea for Zero-injection Agreements.)

However, Furnish said MISO could implement ideas “while we wait on infrastructure.”

Enter MISO’s “partial power” brainchild. The grid operator said in some cases, it probably could serve a portion of large load customers’ needs with existing transmission for an interim period. Load then could be scaled up incrementally as generation or transmission is constructed. Finally, once construction is complete, the full load could be served with firm withdrawal capability at its interconnection point.

Furnish said providing service to fractions of load “helps address the challenges of using the system that is available and manage service as conditions change.” She said a ramp-up to firm service allows service even as upgrades come online.

Furnish said discussions on partial service applications similarly will be held at Planning Advisory Committee meetings.

Butz cautioned that MISO and members need to focus on energy adequacy because new large load customers have “twice the load factor” of MISO’s average load. He said the load surge comes as MISO’s highest-capacity-factor thermal resources plan to retire in droves.

“It’s really crucial that we understand how to serve high-load-factor load,” Butz said.

Chatterjee said MISO will strive to create “timely paths” for integrated large loads but “must keep the system reliable today and in the future.”

Chatterjee said MISO would examine which initiatives it could move fast on “without boiling the ocean.” She said the RTO already has done the “foundational work” to open up grid capacity through its expedited transmission project work.

Furnish also said MISO wouldn’t “copy and paste” other RTOs’ proposals in the large load space but is evaluating their work.

Reserve Product Revamp

Additionally, MISO said it needs to recalibrate its reserve products to account for greater uncertainty introduced by large loads.

Director of Reliability Coordination John Harmon said the “behavior of large load” isn’t reflected today in MISO’s ancillary service setup. He said it probably will have to keep more reserves and revise reserve products’ demand curves.

Harmon said large loads can quickly increase or decrease demand, especially when co-located generation or the load itself suddenly goes offline.

Harmon said the Reliability Subcommittee would handle modernizing the reserve scheme and noted the group already is working to create a dynamic regulation and ramp product that calls up a greater volume of reserves as system uncertainty rises.

Stakeholders asked what role MISO sees itself playing in controlling added costs on the system from load growth.

Bakke said that while MISO cannot influence much of the consumer costs that come with large loads, it views itself as responsible for cost-effective regional transmission planning to minimize the volume of more expensive, piecemeal transmission upgrades. He said the RTO likely must overhaul some of its process for furnishing reserves, since it expects that reserves will be used more often.

MISO will hold three more workshops on large loads over 2026: on April 30; July 31; and Oct. 29.