Entergy seeks waiver of Midcontinent ISO rules that cut accreditation for key generators

Entergy Services is seeking a waiver from some of the new seasonal capacity accreditation requirements in Midcontinent Independent System Operator, because the new approach decreases the capacity value of some fossil fuel-fired plants enough that the company may have a capacity shortfall in Mississippi.

"Entergy Arkansas and Entergy Mississippi are facing dramatic decreases in the capacity accreditation of the resources due to the application of MISO's new accreditation methodology," Entergy said in a waiver request filed with the Federal Energy Regulatory Commission.

The new MISO rules cut accreditation for one of Entergy Mississippi's largest gas-fired units by 25%, the waiver request said. The company is seeking a waiver for the next three auctions and it asked FERC grant the waiver by March 7, in time for the auction that will close at the end of March 2023.

At issue is MISO's new seasonal resource adequacy construct (ER22-495), approved by FERC Aug. 31. Under the new rules, MISO's planning resource auction will clear separately for each season. MISO also changed the accreditation for conventional resources to be based in part on historic average capacity available in times of highest need, rather than the prior approach based on installed capacity adjusted for forced outages.

If a resource is offline and has a startup time longer than 24 hours, it is considered unavailable for MISO's resource adequacy hours, according to the new rules.

Entergy request

Entergy says that the start-time requirement unfairly reduces the accreditation of some of its resources. For instance, Entergy Mississippi owns 100% of the 738-MW gas-fired Gerald Andrus plant in Greenville, Mississippi, and the plant is one of Entergy Mississippi's largest generators, the waiver request said.

The start-up limitation under the new rules will reduce accreditation for this plant from 422 MW on average, to 318 MW on average, the waiver request said. "The decrease in accreditation associated with the use of historical data established prior to the new methodology taking effect will be significantly burdensome," the waiver request said.

The new rules also reduced accreditation for a handful Arkansas coal-fired plants owned in part by Entergy. This includes the Independence 1 plant, where Entergy Arkansas owns 259 MW of capacity and Entergy Mississippi owns 205 MW of capacity. Also affected are Independence 2, where Entergy Mississippi owns 211 MW of capacity, White Bluff 1, where Entergy Arkansas owns 466 MW of capacity, and White Bluff 2, where Entergy Arkansas owns 466 MW of capacity.

Deficit concerns

The decreased accreditation means that Entergy Mississippi is projected to be in a deficit for multiple seasons, the waiver request said. "Moreover, the risk of elevated auction clearing prices is much higher this year than in past years due to the uncertainty around the new seasonal construct and seasonal accreditation rules," the waiver request said.

Entergy says the start-up times for these plants were only slightly above 24 hours and were consistent with MISO's prior rules. Now that the startup times will have significant negative effects on the resources' accreditation values, Entergy has adjusted the startup times at those plants to be less than 24 hours.

Entergy asked FERC to waive the requirement that sets a conventional resource's capacity availability to zero for resources that are offline with a combined start-up time and start up notification time greater than 24 hours, according to the waiver request (ER23-1140) filed Feb. 17.

In its order approving MISO's rules, FERC noted that Zone 10 (Mississippi) and the MISO South subregion are expected to have a capacity surplus overall, suggesting that load serving entities in MISO South will be able to purchase capacity to meet their reserve requirements for the winter season.

MISO does not take a position on the waiver request, Brandon Morris, a spokesperson for MISO, said in a Feb. 21 email. Some other companies from across the MISO footprint have filed similar waivers, he said.