MISO said its members must add an “unprecedented” 17 GW in new resources annually over the next two decades to reliably meet demand and decarbonization goals.

That’s according to the RTO’s finalized Regional Resource Assessment for 2024, which draws on its members’ resource plans to quantify resource expansion needs on a 20-year outlook.

MISO’s Armando Figueroa Acevedo said a 17 GW/year rate would require members to add more than three times their recent average additions of 4.7 GW/year. If members can achieve the more than 340 GW in additions, MISO would boast 515 GW in total installed capacity by 2042.

“Achieving this pace will require several factors, including overcoming supply chain, permitting, labor and interconnection queue delays,” Figueroa Acevedo told stakeholders at a Dec. 18 teleconference to discuss results.

The numbers are in line with results in the draft assessment MISO released in November. (See MISO Prelim Regional Resource Assessment Calls for 343 GW by 2043.)

Members so far have planned to add 163 GW in installed capacity by 2043, less than half of what MISO says is necessary. The RTO filled in a simulated 180 GW of wind, solar and battery storage in its assessment to meet states’ and members’ pollution-cutting goals.

Despite record influxes of renewable energy, Figueroa Acevedo said MISO’s thermal resources are still poised to contribute “the bulk” of accredited capacity by 2043. At that time, MISO expects its lower-accredited wind and solar to account for 62% of installed capacity and have the potential to reach 87% of annual energy.

Between 2029 and 2043, MISO expects 27 GW in thermal retirements and 11 GW in thermal additions, leading to a net loss of 16 GW.

Figueroa Acevedo said MISO’s emerging reliance on solar power is pushing ramping needs from the morning to the evening and will double or triple its average one-hour ramping requirements by the early 2030s.

“A lot of the accredited capacity we see on the system is retained thermal generation and battery storage” entering the system, MISO Director of Strategic Initiatives and Assessments Jordan Bakke said.

WPPI Energy’s Steve Leovy said MISO should consider adding some long-duration energy storage in its modeling. Other stakeholders said the RTO seemed to underestimate how much storage can help improve reliability.

Bakke said the long-term assessment is meant to reflect members’ planning and said next year’s results could change depending on how many new resources members can scale over the next few years. He said the assessment is meant to “highlight the challenges of what we’re collectively trying to do across the footprint.”

MISO’s resource projections in the assessment began with 2029, skipping the next few years, where the RTO has said it could come up short on capacity.

America’s Power CEO Michelle Bloodworth said MISO should be focusing in particular on the next five years, given the heightened danger to reliability. Staff said the Regional Resource Assessment is intended to examine long-term needs while the annual resource adequacy survey conducted by MISO and the Organization of MISO States concentrates on near-term capacity sufficiency.

MISO fared the worst among all regions in NERC’s 2024 Long-Term Reliability Assessment, being the only region categorized as high risk, with NERC calling attention to possible shortfalls starting in 2025. MISO leadership has also raised the possibility of shortages within a few months and said it’s crucial for the grid operator to devise a fast lane in its interconnection queue for necessary generation projects. (See MISO Tells Board RA Fast Lane in Interconnection Queue is a Must.)