1. Lead from the front Texas Nodal http://nodal.ercot.com 1 EDS 3 Release 5 Monday / Friday Market Updates April 18, 2008

2. Lead from the front Texas Nodal http://nodal.ercot.com 2 Agenda Antitrust Admonition Submissions Update –This Week’s Activities –Submissions Status Updates / Questions / Reminders Data Definitions Update LFC Update Q&A / Open Forum Roll Call

3. Lead from the front Texas Nodal http://nodal.ercot.com 3 Antitrust Admonition ANTITRUST ADMONITION ERCOT strictly prohibits Market Participants and their employees who are participating in ERCOT activities from using their participation in ERCOT activities as a forum for engaging in practices or communications that violate the antitrust laws. The ERCOT Board has approved guidelines for members of ERCOT Committees, Subcommittees and Working Groups to be reviewed and followed by each Market Participant attending ERCOT meetings. If you have not received a copy of these Guidelines, copies are available at the Client Relations desk. Please remember your ongoing obligation to comply with all applicable laws, including the antitrust laws.

4. Lead from the front Texas Nodal http://nodal.ercot.com 4 Submissions Status / Submission Times for week of 04/21/08 Due to environment move to Austin, we are not publishing percentages this week Activities for Week of 04/21/08 –Submit the following during prior to the trade date: Note that offer curves cannot be submitted from after market close (10am) until the adjustment period opens (1800) on the day ahead. COP TPO Output Schedule (open to all resources) INC/DEC (DSR resources only) –Submit RT COP adjustments during business hours –Submit RT OS adjustments during business hours

5. Lead from the front Texas Nodal http://nodal.ercot.com 5 Updates / Questions / Reminders FIP / FOP for week of 4/21/08: –FIP: 9.925 –FOP: 23.57 EDS Environment Outages –Update: MMS3 Migration Complete –Outages: No reported stability issues  the known issue we have been tracking 4/15 – Queries slow / non responsive –Root cause – move to MMS3 severed communication to SMTP server (email for notification errors) –Resolved by disabling until network changes are implemented. 4/17 – MMS unavailable –Root cause – lost file mount to market server –Removed server from cluster and remounted –Credit Limit Error ERCOT continues to manually pre-populate the Credit data (historical prices, credit limits, and other supporting data) As this is a manual process, there have been some issues with specific MP’s

6. Lead from the front Texas Nodal http://nodal.ercot.com 6 Updates / Questions / Reminders Three Part Offers – Adjustment Period –If there are problems preventing TPO submissions prior to market close, please submit TPO during adjustment period –This will minimize impact to LMP’s Reminder: QSE’s Performing ICCP Maintenance: –ERCOT is closely monitoring ICCP / Telemetered Data –If you have a planned maintenance period: Send a notification to eds2@ercot.comeds2@ercot.com Include the following information –Date/time of maintenance –Expected duration –This will prevent ERCOT from contacting MP’s when issues are found

7. Lead from the front Texas Nodal http://nodal.ercot.com 7 LFC 6.3 pre-Test (REMINDER) UPDATE: ERCOT is currently evaluating EOC spreadsheets –We will reach out to QSE’s where we see any issues REMINDER: Open Loop Testing –4/25 from10-noon –5/5 from 4-6pm –5/12 from 7-9am –On these dates: QSE’s will submit a “deconstructed” zonal, portfolio-level offer as a resource specific, nodal TPO QSE TPO’s will be submitted into the RT market in the adjustment period –Please ensure: Appropriate staff are available to support submissions ICCP data is of good quality This is imperative to ensure a meaningful exercise on these dates REMINDER: ERCOT to provide QSEs with settlement impact resulting from OOME and Local Balancing had units followed SCEB BP Please refer to details provided during the 3/14 workshop: http://www.ercot.com/calendar/2008/03/20080314-EDS3-6.html http://www.ercot.com/calendar/2008/03/20080314-EDS3-6.html

8. Lead from the front Texas Nodal http://nodal.ercot.com 8 Target Dates for 6.3 Tests Week of June 16 th – 2 hour test Week of July 7 th – 8 hour test Week of July 28 th – 48 hour test

9. Lead from the front Texas Nodal http://nodal.ercot.com 9 Data Definitions: Overview Information: 1.Goal of Data Definitions release is: –Clarify objects and attributes for the MMS and CRR projects. –Augment existing EDS 1 – EDS 3 Release 7 objects. 2.Changes at this release: –EMS objects have been removed. –EMS object’s definitions have been updated. 3.Known limitations are: –Some descriptions are missing/ lacking. –Attribute length and precision data is not included. 4.Please review and make suggestions –Missing data objects, attributes, enumerations, descriptions.

10. Lead from the front Texas Nodal http://nodal.ercot.com 10 Data Dictionary is Available: Initial Data Dictionary draft and covering slide deck will be posted today on the Nodal website (‘IDA - ERCOT Data Definitions v0.9.zip’) –http://nodal.ercot.com/docs/pd/ida/index.html#oth (under ‘General IDA Documents’ section)http://nodal.ercot.com/docs/pd/ida/index.html#oth –http://nodal.ercot.com/readiness/index.html (under ‘Key Documents’ section)http://nodal.ercot.com/readiness/index.html

11. Lead from the front Texas Nodal http://nodal.ercot.com 11 Next Release: Future releases will be in lockstep with the External Interface Specification from the EIP project which is projected for the middle of May. The release will include: 1.The addition of new object definitions. 2.Updates and/or clarifications to existing objects. 3.Available precision information. Please provide suggestions on this release via e-mail to eds3@ercot.com by May 1st in order to make the next versioneds3@ercot.com

12. Lead from the front Texas Nodal http://nodal.ercot.com 12 LFC Phase II Testing Results for week of 4/14 –LFC 6.2 pre-test Tenaska –LFC 6.2 test Suez In-Process NRG Scheduled Test: week of 4/21 –LFC 6.2 pre-test APX Monday 11:00 AM BTU Tuesday 9:00 AM FPL Tuesday 1:00 PM Coral Wed. 9:00 AM Luminant Wed. 1:00 PM APX Thursday 9:00 AM AEN Thursday 1:00 PM –LFC 6.2 test Suez Monday 8:00 AM Remember to submit test forms 2 business days before Test The Date & Time Format for the test file is MM/DD/YYYY HH:MM Submit to LFC@ercot.comLFC@ercot.com

13. Lead from the front Texas Nodal http://nodal.ercot.com 13 LFC Phase III Pre-Test Pre-Test Schedule –LFC Pre-test Flat Load Test Week of April 28 th –LFC Pre-test Up Load Test Week of May 5 th –LFC Pre-test Down Load Test Week of May 12 th Test Support Activities & Submittals –QSEs with Resources must submit TPO, COPs, Output Schedules, Inc/Dec offers that will produce SCED dispatches similar to their Balancing energy –QSEs with Resources must ensure their GMS systems are on and providing good data to ERCOT (MW, MVAR, Status, Limits, AS, etc...) –TSPs are asked to ensure their EMS systems are on during these tests and they also provide accurate data to ERCOT over ICCP Submit Submittals & Questions to LFC@ercot.comLFC@ercot.com

14. Lead from the front Texas Nodal http://nodal.ercot.com 14 Q&A Q&A / Open Forum