MISO staff warn of continued capacity shortfall

The Midcontinent Independent System Operator (MISO) is at risk of continued resource capacity shortfalls in coming years because of planned US power plant retirements and expected growth in electricity demand, according to a draft report from the grid operator's staff.

The grid could need more than 100GW of new nameplate capacity by 2030 and 200GW by 2041 to meet electricity load and utility company decarbonization goals, staff members told MISO's resource adequacy subcommittee on 24 August.

MISO staff tied much of the increased need for nameplate capacity to expected decreases in accredited resources as more traditionally baseload coal-fired power plants are replaced with renewable generation, which MISO tends to rank lower in terms of being able to reliably provide power to the grid. MISO staff projected renewables would grow to 30pc of the grid's annual energy by 2027 and may account for as much as 60pc of the grid's power output by 2041. Meanwhile, generators plan to close a little under 34,000MW of coal-fired power plant capacity in the grid and 12,000MW of natural gas by 2041, and add more than 60,000MW of wind, solar and battery resources.

With the energy transition, the amount of currently existing nameplate capacity in MISO will shrink to 146,000MW in 20 years' time from 196,000MW this year, and existing accredited capacity will drop to 112,000MW from 162,000MW.

MISO is also expecting capacity factors at coal and natural gas units to decline. But MISO expects electricity demand on the grid to grow over that time period.

Some parts of the grid are already facing challenges.

MISO's north and central regions had a combined roughly 1,200MW shortfall in the grid operator's 2022-23 planning resource auction in April. And the grid operator requested generator Ameren delay retiring two units of the Rush Island coal-fired power plant, which had been scheduled to close this year.

The capacity deficit could be system-wide next year if generators' addition plans are delayed and companies move forward with planned retirements, MISO staff warned last week. Even if new power is installed as planned, there could be a deficit in capacity across the grid in 2027, they said in slides of their draft report presentation.

In 2027, the amount of accredited existing capacity in MISO may have shrunk to 141,000MW from 162,000MW this year, grid operator staff projected.

MISO serves about 42mn people in 15 central US states and parts of Canada.

By Courtney Schlisserman