MISO has signaled an openness to alter its 31-day planned outage rule for units that signed up to be capacity resources.

MISO said it experienced significantly more outages in summer 2025 compared to recent years, “which contributed to tight system conditions.” The upsurge has MISO revisiting its generator planned outage rules.

MISO expects capacity resource owners to either procure replacement capacity or pay penalties if they are offline for more than 31 days in a season. They must notify the RTO 120 days in advance of planned outages to be exempt from capacity accreditation reductions.

Davey Lopez, manager of market design resource planning, said MISO will examine whether its outage rules are rewarding availability, as MISO intended, and determine if they need an overhaul. At a Nov. 12 Resource Adequacy Subcommittee meeting, Lopez said MISO now has three planning years of data to evaluate the impacts of its move to seasonal capacity auctions and outage rules.

The RTO’s 31-day outage rule has been in effect since FERC approval in August 2022.

WEC Energy Group’s Chris Plante said he believes generation owners aren’t as concerned about their forced outage rates anymore under MISO’s availability-based capacity accreditation. Other stakeholders agreed that unit owners are less worried about their forced outage rate and more preoccupied with being available during the predefined risky hours in a season, which MISO has placed a premium on per its availability-based accreditation.

Lopez said MISO’s evaluation would look for “unintended consequences” and assess whether the ruleset “continues to provide the proper incentives for resources to be available during the periods of highest reliability risk and prudent planned outage scheduling.” He stressed that MISO doesn’t yet have any revisions in mind.

Lopez said he would appear before the RA Subcommittee in early 2026 for more discussion.