NOTICE DATE: September 11, 2026

NOTICE TYPE: M-B091126-01 Financial/Credit

SHORT DESCRIPTION: Seasonal Variability in the Look-Back Period for RTLE of EAL Formula

INTENDED AUDIENCE: All Market Participants

DAYS AFFECTED: September 16, 2026

LONG DESCRIPTION: On September 16, 2026, the Estimated Aggregate Liability (EAL) component of the Total Potential Exposure (TPE) calculation (ERCOT Protocol Section 16.11.4.3, Determination of Counter-Party Estimated Aggregate Liability) will transition to the non-summer look-back period for Real-Time Liability Estimated (RTLE).

As part of the seasonal variability applied to RTLE, the look-back period will be:

• 20 days from September 16 through May 15 (non-summer months); and
• 40 days from May 16 through September 15 (summer months).

Effective September 16, 2026, the RTLE look-back period will therefore change from 40 days to 20 days.

The look-back period for traders remains unchanged at 20 days.

Please monitor your Credit Monitoring and Management Reports and manage collateral accordingly.

ADDITIONAL INFORMATION: This seasonal variability was implemented as part of NPRR1277, Revisions to EAL Formula.

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.

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