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NOTICE DATE: April 20, 2021

NOTICE TYPE: M-A042021-01 Operations

SHORT DESCRIPTION: Incorrect Parameters in Market Management System on Operating Days March 24 to 26, 2021

INTENDED AUDIENCE: All Market Participants

DAYS AFFECTED: March 24 to 26, 2021

LONG DESCRIPTION:  On March 24, 2021, an internal data error occurred during a routine database load, which caused several Market Management System (MMS) parameters to be replaced with incorrect values.  ERCOT discovered that this error may have impacted Real-Time Market (RTM) prices, due to the impact of the error on Security-Constrained Economic Dispatch (SCED).

More specifically, this error resulted in SCED executions between 00:35 on March 24, 2021, and 20:45 on March 26, 2021, using incorrect values for certain SCED parameters in some, but not all, SCED intervals.  The table below describes each of the impacted SCED parameters, its correct and incorrect values for the time period at issue, the time period during which incorrect values occurred, and a brief description of the potential impact on SCED.

SCED Parameter

Correct Value

Incorrect Value

Impacted Time Period

Potential Impact to SCED

System-wide Offer Cap



3/24/2021 00:35 to 3/24/2021 00:55

May have impacted proxy Energy Offer Curves (EOCs)

Upper Energy Offer Protection Price



3/24/2021 00:35 to 3/24/2021 00:55

May have impacted proxy EOCs


1 MW

0.01 MW

3/24/2021 00:35 to 3/26/2021 17:30

May have impacted proxy EOCs

Over-generation Penalty Price


$3,001/MWh and $5,000/MWh

3/24/2021 00:35 to 3/26/2021 20:35

No impact observed

Power Balance Penalty Curve

Multiple values from $250/MWh to $2,001/MWh

$3,001/MWh and $5,000/MWh

3/24/2021 00:35 to 3/26/2021 20:35

May have impacted SCED intervals when System Lambda exceeded the lowest price on the Power Balance Penalty Curve of $250/MWh

ECI Threshold 2



3/24/2021 00:35 to 3/26/2021 20:45

May have impacted mitigation of Resource offers as part of the SCED Constraint Competitiveness Test (CCT) process

DME ECC Threshold



3/24/2021 00:35 to 3/26/2021 20:45

May have impacted mitigation of Resource offers as part of the SCED Constraint Competitiveness Test (CCT) process


Proxy Energy Offer Curves impacted by this error will be reflected in the 60-day SCED disclosure reports for the relevant Operating Days. 

Because the error impacted SCED, RTM prices may have been impacted.  ERCOT Protocol Section 6.3(4) requires ERCOT to correct RTM prices when, among other reasons, (i) a Market solution is determined to be invalid, (ii) invalid prices are identified in an otherwise valid Market solution, or (iii) the Base Points received by Market Participants are inconsistent with the Base Points of a valid Market solution, unless accurate prices cannot be determined.  Although the error may have affected prices during the impacted SCED intervals, ERCOT cannot determine accurate prices because any effort to recalculate prices would require ERCOT to make significant assumptions concerning the operating behavior of individual Resources over extended periods of time. Therefore, ERCOT will not seek review of RTM prices for the impacted Operating Days by the ERCOT Board of Directors.

Incorrect parameters were also put in the Day-Ahead Market (DAM) and Reliability Unit Commitment (RUC) applications as part of the routine database load process.  However, these parameters were corrected before impacting results for either the DAM or RUC.

Finally, ERCOT has made changes to its database load processes to address similar concerns moving forward.  Changes from the vendor are also being pursued to further mitigate future concerns.

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 [log in to unmask].

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