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NERC files final Order 901 milestone on inverter-based resource studies

The November 4 proposals cover operational and planning studies. A filing is not final FERC approval.

By Greener Numbers Editorial Team · Published November 4, 2026 · Updated 11/4/2026

NERC said on November 4 that it filed proposed reliability standards with the Federal Energy Regulatory Commission to complete the fourth and final milestone under FERC Order No. 901. The filing addresses risks associated with inverter-based resources. It is a standards proposal submitted to FERC, not an announcement that the regulator has approved the new requirements.

The package advances two standards-development projects: Project 2025-03 for operational studies and Project 2025-04 for planning studies. NERC says they are intended to improve how inverter-based resources are represented and evaluated in those studies as the electricity resource mix changes.

Operational studies and planning studies have different time horizons, but NERC presents both projects as part of improving assessments of grid performance. The announcement describes the objective of the standards work. It does not provide a measured reduction in outages or a quantified reliability benefit already delivered by the filing.

The work follows earlier milestones under Order No. 901. NERC says its Milestone 3 filings last November focused on model validation, data sharing and electromagnetic transient modeling. Those earlier filings and the current operational and planning proposals are separate steps in the broader standards program.

NERC credits industry engagement and technical collaboration for completing the filings. Completing its submission milestones does not mean its work on inverter-based resource reliability has ended. The organization says standards development, technical assessments, performance analysis, registration and stakeholder collaboration will continue.

For readers following the grid integration of clean-energy resources, the next distinction is between a filing and regulatory action on that filing. The November 4 announcement does not set out a final FERC approval or an effective date for the proposed requirements. It also does not announce a new electricity price or promise a specific customer bill saving.