CARMEL, Ind. — MISO members will likely have to add 343 GW of installed capacity by 2043 to meet state policy goals while maintaining resource adequacy, the RTO said in preliminary results from its annual Regional Resource Assessment.

Of that 343 GW, members have already planned to add 163 GW in installed capacity. According to its early results, MISO said that leaves members filling in an additional 180 GW over the next 20 years.

“Achieving 343 GW of additional installed capacity by 2043 would require an average installation of 17 GW per year over the next 20 years to achieve, which is more than 3.5 times greater than the recent installation rate,” MISO Director of Strategic Initiatives and Assessments Jordan Bakke told the Resource Adequacy Subcommittee on Nov. 6.

From 2020 through 2022, MISO experienced an average 4.7 GW/year worth of installed capacity additions. Between 2029 and 2043, MISO foresees 27 GW in thermal retirements and 11 GW in thermal additions based on its members’ plans.

Bakke said that by 2043, MISO also estimates that wind and solar would account for 62% of installed capacity and have the potential to reach 87% of annual energy served.

“The purpose is not to speculate on the resource buildout but report back on what our members are planning,” Bakke said of MISO’s assessment.

MISO remains adamant that in 20 years’ time, the loss-of-load risk will move away from afternoon summer hours to concentrate in early mornings in winter. MISO also said systemwide ramp-up needs will pick up, with peak ramping needs occurring outside of summer and in evening, rather than morning, hours.

The number of additional megawatts MISO is signaling a need for is up sharply from 2022, when its assessment found members likely needed to add 200 GW of new installed capacity by 2041. (See MISO: 200 GW in New Capacity Necessary by 2041.)

In November 2023, a condensed version of the assessment also observed that retirement announcements are trouncing stated capacity additions. The grid operator said that beyond what members are planning, the footprint likely needs an additional 13 GW of accredited (not installed) capacity by 2027, 27 GW by 2032 and 34 GW by 2042 to fulfill demand. (See MISO Continues to Find Mounting Retirements, Inadequate New Capacity in Abridged Resource Assessment.)

MISO will hold a dedicated stakeholder workshop Dec. 18 to go over final results of the assessment.