MISO’s Independent Market Monitor has called for the RTO to change how it manages its Midwest-South transfer limit in ways he contends will open line capacity and reduce costs for Midwest market participants.

IMM David Patton asked MISO to create more steps on the limit’s transmission constraint demand curves to use more megawatt space on the transmission path and create headroom for deviations.

At a Sept. 30 MISO Market Subcommittee meeting, Patton said the Midwest-South limit has been binding more frequently since 2022 and contributed to $41 million in congestion over summer 2025, a 121% increase over 2024.

He said the regional transfer constraint has been used more in recent years due to solar additions in the South, a prolonged drought in Manitoba that has the Midwest exporting more power than usual and a drop in natural gas prices that has made MISO South’s plentiful gas generation more attractive.

Patton said reformulated demand curves on the transfer limit would allow greater energy transfer capability, increased use of MISO South generation and reduced costs to loads in MISO Midwest. He said adjusted curves could allow the RTO to tap into more than 200 MW on average in the South and increase flows by 50-60 MW.

Patton contended that adopting his demand curve recommendations would have reduced Midwest average energy prices by $3.48/MWh and driven down the region’s market costs by $515 million just over summer 2025.

Patton said that he’s long advocated MISO renegotiating its contracts with SPP and other neighbors to stipulate how MISO is allowed to use the transfer limit. He said because the transfer limit is a “contractual constraint that does not reflect any physical limits,” MISO should work to get more out of it.