EDS 3 Release 5 and 6 Friday Market Updates Sept 19, 2008 http://nodal.ercot.com 1

Submission Metrics Update Updates / Questions / Reminders Agenda Antitrust Admonition SCED Update Submission Metrics Update Updates / Questions / Reminders LFC / State Estimator Update Q&A / Open Forum Roll Call http://nodal.ercot.com 2

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. http://nodal.ercot.com 3

Submission Metrics Update 9/14/2008 9/15/2008 9/16/2008 N/A 76% 14 73% 25 72% 22 COP TPO IDO OS 9/17/2008 9/18/2008 9/19/2008 N/A 73% 22 72% 21 76% COP TPO IDO OS Submit the following for each trade date: Three Part Offer or Output Schedule EOC only required. Should cover 80 – 120% of cost Min Energy / Start-up may be zero’d out FIP/FOP must sum to 100% COP Only required if submitting an Output Schedule No updates in the adjustment period required Note: a COP is also required in order to submit during the adjustment period (this will be changed to a warning in the next release of MMS  MMS4) http://nodal.ercot.com 4

Updates / Questions / Reminders Unplanned Environment Outages MIS 9/08 09:00AM – 01:00PM LMP Contour Map not Updating. not publishing to MIS. API Sub Group The API Sub-Group will be merged into the EDS 3 Friday calls Effective date 9/26/08 We will reserve the last agenda item for these topics Roll call will be taken at the beginning of calls so that non-technical attendees may drop off the call This will continue until EDS starts again where a determination will be made on whether it warrants a full timeslot on Fridays The last API Sub-Group meeting will occur 9/23/08 http://nodal.ercot.com 5

Updates / Questions / Reminders WebEx Next Week for Last Phase of Nodal RARF’s Date / Time: 9/25 10am – 12pm Will cover the schedule and plan for next three months Objective is to wrap up RARF project by the year’s end http://nodal.ercot.com 6

LFC Update: Focused SE Days Week 5 Convergence for 9/2/08 was 96.17% Convergence for 9/3 was 97.13% http://nodal.ercot.com 7

LFC Update: Focused SE Days Week 5 Convergence for 9/4/08 was 97.04% Week 5 Summary: Telemetry much high quality and availability than in previous windows Only issue is QSE availability to fix issues outside of regular business hours http://nodal.ercot.com 8

LFC Update: Focused SE Days Week 6 Convergence 9/8/08 was 96.99%. Convergence for 9/9/08 was 99.03%, http://nodal.ercot.com 9

LFC Update: Focused SE Days Week 6 Convergence for 9/10/08 was 98.15%. Convergence for 9/11/08 was 97.67%. http://nodal.ercot.com 10

LFC Update: Focused SE Days Week 6 Convergence for 9/12/08 was 85.02 %. Accelerated contacts to market participants and Nodal systems support personnel helped improve the convergence percentages for this test compared to FIT 1. Telemetry was much cleaner for this test period compared to the previous 5 http://nodal.ercot.com 11

Q&A Q&A / Open Forum http://nodal.ercot.com 12