How accredited capacity is determined
MISO’s accredited capacity process is all about ensuring that resources can reliably meet demand during critical periods. The methodology varies depending on the type of resource, reflecting the unique characteristics of each. Let’s dive into how MISO approaches this for thermal generation, renewables, demand response, and storage.
Thermal resources: reliability through historical performance
Thermal generation resources, like coal and natural gas plants, are accredited based on their historical performance during critical hours in each season. MISO applies seasonal forced outage rates to the installed capacity (ICAP) of these resources to calculate their Seasonal Accredited Capacity (SAC). This ensures that only the reliable portion of a resource’s capacity is counted toward meeting resource adequacy requirements. For new thermal resources without sufficient historical data, MISO assigns a class average until enough performance data is available to refine the calculation.
Renewable resources: accounting for variability
Renewable resources, such as wind and solar, are evaluated differently due to their intermittent nature. Wind resources are accredited based on Effective Load Carrying Capability (ELCC) studies, which assess their ability to contribute to reliability during peak demand periods. Solar resources follow a similar ELCC-based approach. For new renewable projects, MISO assigns a class average until sufficient operational data is collected. This methodology ensures that the variability of renewables is accurately reflected in their accredited capacity.
Demand response: leveraging flexibility
Demand Response Resources (DRRs) are unique in that they reduce demand rather than generate electricity. MISO accredits DRRs based on their historical performance and availability during emergencies. These resources must be registered and meet specific requirements to qualify as Load Modifying Resources (LMRs). Once accredited, they receive 100% of their capacity rating for the planning year, provided they meet documentation and verification standards.
Storage resources: adapting to new technologies
Electric Storage Resources (ESRs), such as batteries, are accredited based on their ability to inject electricity into the grid during critical periods. MISO evaluates their type and volume of interconnection service, as well as their historical performance and availability. For hybrid resources that combine storage with generation, the accreditation process considers both components to determine the overall capacity contribution.
Recent updates to miso’s accreditation methodology
MISO has been refining its accreditation methodologies to better align with the evolving energy landscape. One significant update is the introduction of seasonal resource adequacy requirements, which began in 2023. This shift recognizes that resource availability can vary significantly across seasons, particularly for renewables and demand response. By calculating Seasonal Accredited Capacity (SAC) for each resource type, MISO ensures a more accurate representation of their reliability throughout the year.
Another key change is the extended use of ELCC studies for renewable resources, which provide a more nuanced understanding of their contribution to grid reliability. These updates reflect MISO’s commitment to adapting its processes to accommodate the growing share of renewables and storage on the grid.
Why accredited capacity matters for resource adequacy
Accredited capacity is the cornerstone of MISO’s resource adequacy framework. By accurately assessing the reliability of each resource type, MISO ensures that there’s enough capacity to meet demand during peak periods. This process not only supports grid reliability but also helps market participants plan and invest in resources that align with MISO’s requirements.
For example, a wind farm with a high ELCC rating can confidently participate in the market, knowing its capacity will be recognized. Similarly, demand response providers can leverage their flexibility to contribute to resource adequacy while earning revenue. These calculations ultimately create a balanced and reliable energy market that benefits all stakeholders.
Looking ahead: the future of resource accreditation in MISO
As the energy landscape continues to evolve, MISO’s accreditation methodologies will likely see further updates. The growing integration of renewables and storage, coupled with advancements in demand response technologies, will require ongoing adjustments to ensure the grid remains reliable. By staying ahead of these changes, MISO is paving the way for a more sustainable and resilient energy future.
Understanding how MISO calculates accredited capacity is essential for anyone involved in the energy market. Whether you’re a market participant, policymaker, or energy enthusiast, these methodologies provide a glimpse into the complex processes that keep the grid running smoothly.
