NOTICE DATE: October 3, 2025

NOTICE TYPE: M-A092624-04 Operations

SHORT DESCRIPTION: The RTC+B - System Operations Test Environment (RTC+B SOTE) will be available to Transmission Service Providers (TSPs) starting October 6, 2025.

INTENDED AUDIENCE: All Market Participants

DAYS AFFECTED: October 6, 2025

LONG DESCRIPTION: The RTC+B SOTE will be available to TSPs starting October 6, 2025, and can be used to test the Outage Evaluation (OE) 90-day ahead cases for January ML1 (Single Model).

ERCOT will continue to approve 60-day and 90-day-ahead outages using the current ESR Combo Model throughout October, and will use the existing System Operations Test Environment (SOTE) system for any coordination with TSPs regarding outage approvals.

Starting in November, ERCOT will begin using OE60-day (January model) and OE90-day (February model) RTC+B cases for 60-day and 90-day ahead outage evaluation studies. A 60-day and 90-day case will also be available to TSPs for their outage studies in RTC+B SOTE system.

Updated and attached the SOTE Outage Studies document with details that help on RTC+B SOTE system.

CONTACT: If you have any questions, please contact your ERCOT Account Manager. You may also call the general ERCOT Client Services phone number at (512) 248-3900 or contact ERCOT Client Services via email at ClientServices@ercot.com.

If you are receiving email from a public ERCOT distribution list that you no longer wish to receive, please follow this link in order to unsubscribe from this list: http://lists.ercot.com.

dg