NERC Credits MISO Batteries at 97% Peak Capacity But Duration Gap Leaves Baseload Case Unsettled
High peak-contribution scores for storage sit alongside rising coal and gas outage rates, yet short battery duration keeps baseload displacement from being proven.
NERC's 2026 State of Reliability assessment credited MISO's roughly 3.6 GW of battery storage with a 97% peak load contribution — the highest endorsement the regulator has given any storage fleet and well above how grid planners have traditionally rated intermittent resources. The same report gave MISO's 20.4 GW of solar a 60% peak contribution rating.2
Both figures land against a backdrop of worsening conventional generator performance. NERC reported that coal unit unavailability rose by 39.8 TWh in 2025 and gas unit unavailability by 19.1 TWh. The overall availability of conventional generation fell, "largely driven" by those declines, according to NERC's own language.3
The combination is the strongest argument yet for treating storage as a serious capacity resource rather than a seasonal supplement. Batteries showing up at 97% of nameplate when the grid needs them most, while coal and gas plants increasingly do not, shifts the reliability arithmetic that has underpinned baseload planning for decades.2,3
The SPP data point in the same NERC assessment reinforces this. SPP's 3.9 GW of solar received a 54% peak contribution rating and its 1.3 GW battery fleet 84%. These are not theoretical capacity factors; they are measured contributions at system stress moments.2
But peak-hour effectiveness and baseload displacement are different things. A battery delivering 97% of nameplate for two hours is genuinely valuable. It is not performing the same function as a combined-cycle gas plant running at 80% capacity factor through a six-week heat event. NERC's peak contribution metric captures one dimension and ignores the other.2
Duration is the hard constraint. Until storage economics support 8-to-12 hour discharge at scale, batteries can firm peaks and defer outages but cannot replicate the continuous energy output that coal and gas provide during extended stress periods. The Lincoln, Nebraska project illustrates the current deployment pattern: a 3 MW/12 MWh zinc-based battery added to a 30 MW microgrid serving government and public safety facilities — a four-hour resilience asset, not bulk energy replacement. Eos is supplying at least two U.S. projects with over 100 MWh of capacity, including a 36 MW/216 MWh installation in Springfield, Missouri, part of SPP. Meaningful projects, but sized for specific load firming rather than coal retirement.5
The demand side complicates the picture further. NERC flagged data center customer-initiated load reduction events in February 2025, including 1.8 GW shed voluntarily in the Eastern Interconnection during a transmission fault and a separate 428 MW event the same month. NERC described these as demonstrations of a capability that changes how planners model demand.3
A load that can voluntarily drop 1.8 GW in real time is a different planning input than traditional industrial demand. It also means the peak demand forecast that batteries are being credited against carries more uncertainty than the clean 97% figure implies.2,3
AI data center growth cuts both ways here. Rising computational demand pushes electricity consumption higher, which is the argument for maintaining dispatchable fossil capacity. Yet those same facilities are being built with on-site generation and controllable load, potentially reducing their grid draw precisely when storage assets are credited to cover peak.1,3
The clearest available evidence of actual coal displacement comes from Australia. Origin Energy is building a battery with approximately 3.8 hours of discharge at the site of Australia's largest coal-fired power station, with a second stage expected online in early 2027 bringing total capacity to 700 MW/3,160 MWh. That is a decommissioned coal site being directly repurposed — a more honest test of displacement than any greenfield microgrid.4
What NERC's headline figures do not show is the duration curve behind the peak credit. A 97% contribution score on a two-hour battery and a 97% score on an eight-hour battery represent fundamentally different grid assets, and the regulator does not draw that distinction in its published ratings. Until that granularity appears in reliability assessments, the case for reducing baseload because storage is on the system rests on peak capacity metrics alone — while the coal and gas outage data keeps accumulating on the other side of the ledger.2,3