NOTICE DATE:  December 4, 2009

NOTICE TYPE:  M-D120409-01 Extracts

SHORT DESCRIPTION:  Revised rounding of Load and Generation values

INTENDED AUDIENCE:  QSE Settlements personnel

DAY AFFECTED:  Beginning with extracts posted on November 23, 2009

LONG DESCRIPTION:  On November 21, 2009, ERCOT migrated the initial phase of PR-80027 (advanced metering project). As part of this project, the data aggregation code was rewritten in order to achieve performance improvements for the nodal project. The new data aggregation code rounds generation and load values differently than the previous code. Before November 21, generation values were rounded to 16 decimal places and load values were rounded to 4 decimal places. The new code rounds both load and generation values to 6 decimal places. This change can result in small differences in both Resource Imbalance quantities and Load Imbalance quantities when compared to previous settlements.

Several Market Participants have reported small differences in Resource Imbalance quantities when compared to the previous settlement of the same Operating Day. This difference first appeared on Final and True-up settlements posted on November 23, 2009. The largest change reported has been 0.0001 MWHs. This change will be in effect for all Operating Days settled after November 20.

ERCOT is also revising the “Generation Site Verification Guide”, located on the ERCOT website, under Data Aggregation for the above change to rounding (http://www.ercot.com/mktinfo/data_agg/ssig/index). The revised guide will be posted tomorrow.

ADDITIONAL INFORMATION:  Information related to Project PR-80027 is located on the ERCOT website at http://www.ercot.com/services/projects/current/80027_01/index

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 e-mail at [log in to unmask].

If you are receiving e-mail from an 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.

ad