1. http://nodal.ercot.com 1 Market Trials Real-Time Market / LFC Weekly Update April 9, 2010

2. 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. DISCLAIMER All presentations and materials submitted by Market Participants or any other Entity to ERCOT staff for this meeting are received and posted with the acknowledgement that the information will be considered public in accordance with the ERCOT Websites Content Management Operating Procedure.

3. http://nodal.ercot.com 3 Agenda Antitrust Admonition Environment Report –Planned / unplanned outages –Known Issues Standing Reports and Updates –General reminders / updates –RTM / LFC Update –LFC Update: Status of Individual QSE Tests for LFC –Telemetry Outreach Update –State Estimator Convergence Statistics Question and Answers / General Discussion ERCOT asks that Market Participants log into the WebEx session using their company name and then their name. This will allow ERCOT to take roll-call offline

4. Market Trials 2010 Roadmap http://nodal.ercot.com 4

5. http://nodal.ercot.com 5 Environment Report: Planned / Unplanned Nodal Outages Planned Outages –Planned Outages 04/23/10 – 04/25/10 –ERCOT will be performing the initial release for Phase 5 on 4/23—see April 6 Market Notice (http://nodal.ercot.com/readiness/notices/index.html)http://nodal.ercot.com/readiness/notices/index.html –Due to the size and complexity of the release, it will be necessary to take systems down periodically throughout the weekend –ERCOT will be running a series of tests on April 25 which may result in notifications and /or data in the Nodal Production systems that are associated with that test. Unplanned Outages 03/27/10 09:00 A.M. – 4/7/2010 8:00 P.M –Market Manager UI experiencing intermittent periods of unavailability and/or degradation in performance –Update: Teams have released configuration changes into the NPROD environment which appear to have resolved stability issues. Note: ERCOT will be performing site failover testing on 04/10. A brief delay in EWS service availability may occur during this time period.

6. http://nodal.ercot.com 6 Environment Report: Known Issues Real-Time Known Issues List –The Real-Time Known Issues List will be updated April 9 and will deploy over the weekend to the Readiness Center (http://nodal.ercot.com/readiness/markettrials/rtm/index.html)http://nodal.ercot.com/readiness/markettrials/rtm/index.html

7. http://nodal.ercot.com 7 Standing Reports and Updates: General Reminders / Updates Network Model Update –The current system loaded from the model 4/1/10 –Next scheduled loads are 4/14/10 and 5/3/10 Market Trials Phase 5 Handbooks are available on Readiness (see April 1 Market Notice): –Real Time Market / LFC Market Trials Handbook http://nodal.ercot.com/readiness/markettrials/rtm/index.html –Congestion Revenue Rights Market Trials Handbook http://nodal.ercot.com/readiness/markettrials/crr/index.html –Outage Scheduling Market Trials Handbook http://nodal.ercot.com/readiness/markettrials/os/index.html –Day Ahead Activities Market Trials Handbook http://nodal.ercot.com/readiness/markettrials/dam/index.html –COMS Market Trials Handbook http://nodal.ercot.com/readiness/markettrials/coms/index.html –MIS Market Trials Handbook http://nodal.ercot.com/readiness/markettrials/mis/index.html

8. 11/17/2015 http://nodal.ercot.com 8 Real Time Market / LFC Update

9. http://nodal.ercot.com 9 SCED Week 10 Thu 4/1 8:30-9:10 constraint models dual contingency in Denton; units in West to -$33 and local units up to $250 Fewer offer curves and high load on Monday contributed to reaching the $2250 cap (36 intervals) One second LMP telemetry error on 4/1 and 4/5 $112.63 for one minute on 4/7 (SCED triggered due to low frequency and RRS)

10. LMP Missed Interval Reports http://nodal.ercot.com 10 All missed intervals reposted Missed intervals usually due to problem with report trigger not publishing when multiple events running Extended outage on 4/3 due to switching to second MMS server; connection to MIS was broken 4/7 missed interval – SCED triggered by EMS

11. http://nodal.ercot.com 11 LFC Update: Status of Individual QSE Tests for LFC LFC Calendar Status 76 QSEs/Sub-QSEs are currently targeted for Individual QSE tests 63 have scheduled a test window (94% of Generation) 36 QSE/Sub-QSEs have completed testing (80.28% of Generation): The LFC Calendar was updated on April 8 and posted on the Readiness Center at http://nodal.ercot.com/readiness/markettrials/rtm/index.html http://nodal.ercot.com/readiness/markettrials/rtm/index.html AEPCEAGLEMORGAN_SQ4OPTIM_ENERGY AEPSQ3EAGLE_SQ4MP2 ENERGY OPTIMENERGYS Q1 BRAZOSEC_AND_R_SQ6NEXTERAOXY BTUQSEFORMOSANEXTERA_SQ1RIONGL CALPINEFPL_KEIRNEXTERA_SQ2STEC CPSLCRANEXTERA_SQ3STEC_SQ2 CPSSQ1LUMINANTNEXTERA_SQ4TENASKA DIRECTLUMINANTSQ2NRG_SQ1TRQ1_SQ1 DIRECTSQ2MORGAN_SQ3NRG_TEXASTRQ4_SQ4

12. http://nodal.ercot.com 12 LFC Update: Status of Individual QSE Tests for LFC Upcoming LFC QSE Tests Upcoming QSE LFC Tests through April 16: 4/9/2010CALPINE 4/12/2010PSEG (ODESSA) 4/13/2010PSEG (GUADALUPE) 4/13/2010SHERBINO/SILVER STAR (QSE) 4/15/2010MORGAN STANLEY (SQ1, SQ2) 4/15/2010AUSTIN ENERGY 4/16/2010CONSTELLATION Submit questions regarding the LFC Calendar to markettrials@ercot.commarkettrials@ercot.com

13. http://nodal.ercot.com 13 LFC Update: Upcoming Key Dates Upcoming Key Dates for LFC April 16 – Formal testing period closes for individual QSE LFC tests April 19-30 – Re-testing period for individual QSE LFC tests Week of April 19 – The 2-Hour LFC Test Approach document and related artifacts become available for review Week of May 3 – ERCOT will host a workshop to discuss the upcoming 2-Hour LFC Test

14. http://nodal.ercot.com 14 State Estimator Convergence Update State Estimator Daily Convergence Statistics (these percentages are graphed in the next slide) MonthDay% Convergence (Including Solved w/ Mismatch) MAR2997.27 MAR3096.30 MAR3199.31 APR195.96 APR292.59 APR386.67 APR498.90 APR594.54 APR695.07 APR780.75

15. http://nodal.ercot.com 15 State Estimator Convergence Update

16. http://nodal.ercot.com 16 Q&A Q&A / Open Forum

17. http://nodal.ercot.com 17 Appendix

18. http://nodal.ercot.com 18 Market Call Schedule Reminder of market call schedule: 09:00 AM-10:00 AM Outage Scheduling 10:00 AM-11:00 AM Congestion Revenue Rights 11:00 AM-12:00 PM Day Ahead Market / RUC / SASM 12:00 PM-01:00 PM Break 01:00 PM-02:00 PM Real Time Market / LFC –WebEx Details will be posted at: http://www.ercot.com/committees/nodal/mt/ http://www.ercot.com/committees/nodal/mt/

19. http://nodal.ercot.com 19 URLS and EMAIL ADDRESS FOR SUPPORT URLs for access the Nodal Production systems –MIS: https://mis.ercot.com/pps/tibco/mis/https://mis.ercot.com/pps/tibco/mis/ –Market Manager: https://mis.ercot.com/pps/tibco/mis/ Click the ‘Applications’ tab in the upper menu. Link is in the ERCOT Applications portlethttps://mis.ercot.com/pps/tibco/mis/ –CRR: https://mis.ercot.com/pps/tibco/mis/ Click the ‘Markets’ Link in the upper menu. Click CRR in the Market sub menuhttps://mis.ercot.com/pps/tibco/mis/ –EWS: https://misapi.ercot.com/2007-08/Nodal/eEDS/EWShttps://misapi.ercot.com/2007-08/Nodal/eEDS/EWS Reminder: Market Trials email address change: ERCOT asks that MPs use the markettrials@ercot.com email address for questions from this point forwardmarkettrials@ercot.com –This will begin the phasing out of eds2@ercot.com, eds3@ercot.com and eds4@ercot.com email addresses.eds2@ercot.comeds3@ercot.com eds4@ercot.com –A centralized address will no longer require MPs to “guess” which email address to use for their questions –We have implemented a more effective method of routing and responding to emails using this address –The old eds emails can continue to be used until 2009 hold over efforts are completed (such as telemetry outreach)

20. http://nodal.ercot.com 20 Market Trials Handbooks –Available on the Readiness Center at the following links Real Time Market / LFC covering Phase http://nodal.ercot.com/readiness/markettrials/rtm/index.htmlhttp://nodal.ercot.com/readiness/markettrials/rtm/index.html Outage Scheduler covering Phase http://nodal.ercot.com/readiness/markettrials/os/index.htmlhttp://nodal.ercot.com/readiness/markettrials/os/index.html CRR covering release Phase http://nodal.ercot.com/readiness/markettrials/crr/index.htmlhttp://nodal.ercot.com/readiness/markettrials/crr/index.html Settlements / COMs covering Phase http://nodal.ercot.com/readiness/markettrials/coms/index.htmlhttp://nodal.ercot.com/readiness/markettrials/coms/index.html Day Ahead Market http://nodal.ercot.com/readiness/markettrials/dam/index.htmlhttp://nodal.ercot.com/readiness/markettrials/dam/index.html