1. Lead from the front Texas Nodal http://nodal.ercot.com 1 EDS Market Call Bi-Weekly Update Mar 20, 2009

2. Lead from the front Texas Nodal 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.

3. Lead from the front Texas Nodal http://nodal.ercot.com 3 Agenda Nodal market activity update Day-to-day operations summary –Planned and Unplanned ERCOT outages of EDS systems –Future dates of any system upgrades Standing reports and updates –Focused Input Testing –Nodal API sub-group –Reports/Extracts (first meeting of each month) Q&A / General Discussion Deep Dive Topic (different topics each meeting as needed) –Review of EWS performance boundaries / policy changes 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. Lead from the front Texas Nodal http://nodal.ercot.com 4 Nodal Market Activity Update: WMS-Approved Date Changes to Nodal Verifiable Cost Submissions Table 1: Verifiable Cost Submissions by Generator Type Type of GeneratorAbbreviationSubmit By Date* Simple Cycle Greater than 90MW SCGT90June 30, 2009 Simple Cycle Less than or Equal to 90MW SCLE90 July 31, 2009 Gas Steam Non-Reheat Boiler GSNONR Aug 31, 2009 Gas Steam Reheat Boiler GSREH Sep 30, 2009 Gas Steam Super Critical Boiler GSSUP Oct 31, 2009 Combined Cycle Less than or Equal to 90MW CCLE90 Nov 30, 2009 Combined Cycle Greater than 90MW CCGT90 Dec 31, 2009 Coal, Lignite CLIG Jan 31, 2010 Nuclear, Hydro and Renewable NUC, HYDRO, RENEW Feb 28, 2010 Reciprocating EnginesFeb 28, 2010 WMS-Approved Date Changes to Nodal Verifiable Cost Submissions (from COMS Nodal Verifiable Cost Implementation Plan V2 White Paper http://nodal.ercot.com/readiness/golive/index.html ) http://nodal.ercot.com/readiness/golive/index.html

5. Lead from the front Texas Nodal http://nodal.ercot.com 5 Day-to-day operations summary: Planned / Unplanned Outages of EDS Planned Outages –Tuesday, March 17, 2009, 10:00AM until 10:00PM Nodal EMS - Upgrade of the Nodal EMS system and database platform. ICCP data was static periodically during the outage (e.g. basepoints not calculated) –Wednesday, March 18, 2009, 12:00PM until 5:00PM Nodal MIS Reports - Routine maintenance on the server which supports the Nodal MIS Report Services, preventing delivery of reports to MIS. –Thursday, March 19, 2009, 12:00PM until 1:00PM Nodal EDS Sandbox - Release to implement the External Interfaces Specification v1.18 to the Nodal EDS Sandbox environment. The Nodal EDS Sandbox environment was unavailable for ~ ½ hour. Unplanned Outages –3/7 – present – LMP contour map server was decommissioned and will be replaced. The Next generation of the map will be deployed on top of EIS 1.19 / Last Release of MMS and will be available in August. –3/13/09 1:30 PM – 5:00 PM – Nodal Outage Scheduler unavailable. Restarting services resolved the issue. –3/3 – Present – Sandbox notifications throwing errors preventing delivery to MP’s. We are investigating the issue with development. Presently, we have disabled email alerts (to MP’s) for failed notifications.

6. Lead from the front Texas Nodal http://nodal.ercot.com 6 Future dates of any system upgrades Reminders: –EIS version 1.18 is now available at http://nodal.ercot.com/readiness/sandbox/documents/index.html http://nodal.ercot.com/readiness/sandbox/documents/index.html –EIS Version 1.18 EWS deployment (Sandbox only): Deployment completed as scheduled All 1.18 features are now available for testing in the sandbox –EIS Version 1.19 current schedule: Specification to be published on 6/5/09 Sandbox deployment on 7/7/09 EDS deployment on 8/10/09

7. Lead from the front Texas Nodal http://nodal.ercot.com 7 Standing reports and updates: Focused Input Testing Update Next testing will take place 3/24 – 3/26 Reminder: remaining FIT windows will only review telemetry and state estimator convergence. SCED inputs will be removed from FIT until further notice. ALL TIMES ARE CENTRAL DurationStart date and timeEnd date and time 27 hrs (3x9) March 24 - 8:00 amMarch 26 - 5:00 pm 27 hrs (3x9) April 07 - 8:00 amApril 09 - 5:00 pm 27 hrs (3x9) April 21 - 8:00 amApril 23 - 5:00 pm 27 hrs (3x9) May 05 - 8:00 amMay 07 - 5:00 pm

8. Lead from the front Texas Nodal http://nodal.ercot.com 8 Key Numbers -96.07% Test Average Convergence -20 of the 27 Test Hours had 100% convergence -TDSP database failure – 44.4% for Hour 2 of March 11 http://nodal.ercot.com 8 FIT III Assessment reports will be posted at: http://nodal.ercot.com/readiness/eds3/documents/index.htmlhttp://nodal.ercot.com/readiness/eds3/documents/index.html Focused Input Testing (FIT) III, Week 2 – State Estimator

9. Lead from the front Texas Nodal http://nodal.ercot.com 9 Q&A Q&A / Open Forum

10. Lead from the front Texas Nodal http://nodal.ercot.com 10 Review of EWS Performance Boundaries / Policy Changes Deep Dive Topic Mar 20, 2009

11. Lead from the front Texas Nodal http://nodal.ercot.com 11 EWS Policy Changes Utilicast’s findings in Audit Report #9 included an item pertaining to EWS –“The specification for volume limits (message size) and package content (heterogeneous messages) managed by the external web services have not yet been fully defined” –Consequently, there is a risk that transactions submitted by Market Participants may not be processed due to system constraints –In the interest of ensuring reliable market function, ERCOT assessed this situation and determined that changes were required ERCOT’s approach to address this issue is to set and enforce limits on submittals –Limitations in place for the 2008 market trials (file size and composition) will be formalized and documented in the EIP 1.19 release –Minor changes to both, ERCOT’s XML Schema and WSDL will be made to enforce these limits –The External Interface Specification (EIS) will be modified to explicitly state these limitations –Message composition estimates will be provided to help Market Participants assess the impact of these changes on their Web Service usage

12. Lead from the front Texas Nodal http://nodal.ercot.com 12 EWS Policy Changes (Cont.) The following guidelines introduced during previous market trials will be established as policy –Only Homogeneous BidSets will be supported BidSets can contain multiple bids, but all bids must be of the same type –e.g. COP, TPO, OS, etc must be submitted in separate messages ERCOT’s XML Schema will be modified to enforce this restriction –Inbound message sizes will be limited to 3 Mb Size limits will be subject to ongoing review by ERCOT during the upcoming performance testing and market trials WSDL will be modified to enforce message size limit These restrictions exist in the EDS environment today –WSDL and XSD Schema can be used to validate on the client side –At this time, there are no plans to support Heterogeneous BidSets or unlimited request message sizes in the future

13. Lead from the front Texas Nodal http://nodal.ercot.com 13 Average Message Size Estimates Message Type Average Bid Size (Kb) Estimated Maximum Number of Bids (for 3 Mb Payload limit) Assumptions ASOffer18150 One ASOffer for a single ASType. 24 ASPriceCurve instances where each ASPriceCurve is for a single hour of the day 3 OnLineReserves instances per ASPriceCurve instance ASTrade4750 One ASOffer for a single ASType One ASSchedule instance with 24 TmPoint instances where each TmPoint is for a single hour in the day CapacityTrade31000 One CapacityTrade instance with one CapacitySchedule instance The CapacitySchedule instance contains 16 TMPoint Instances COP14200 One COP Instance for a single resource 24 ResourceStatus instances where each ResourceStatus is for a single hour in the day 24 Limit instances where each Limit is for a single hour in the day 24 ASCapacity instances where each ASCapacity is for a single hour of the day CRR7400 One CRR instance One CapacitySchedule instance with 16 TMPoints where each TMPoint is for a single hour in the day 16 MinimumReservationPrice instances

14. Lead from the front Texas Nodal http://nodal.ercot.com 14 Average Message Size Estimates (continued) Message Type Average Bid Size (Kb) Estimated Maximum Number of Bids (for 3 Mb Payload limit) Assumptions DCTieSchedule8375 One DCTieSchedule with one EnergySchedule instance The EnergySchedule instance contains 24 TmPoint instances where each TmPoint is for a single hour in the day 24 NERCTags instances where each NERCTags instance is for a single hour in the day EnergyBid12250 One EnergyBid instance 24 PriceCurve instances where each PriceCurve instance is for a single hour in the day Each PriceCurve instance contains 3 CurveData instances. EnergyOnlyOffer12250 One EnergyOnlyOffer instance 24 EnergyOfferCurve instances where each EnergyOfferCurve instance is for a single hour in the day Each EnergyOfferCurve instance contains 3 CurveData instances EnergyTrade31000 One EnergyTrade instance One EnergySchedule instance that contains 16 TmPoint

15. Lead from the front Texas Nodal http://nodal.ercot.com 15 Average Message Size Estimates (continued) Message Type Average Bid Size (Kb) Estimated Maximum Number of Bids (for 3 Mb Payload limit) Assumptions IncDecOffer14200 One IncDecOffer instance 24 FipFop instances where each FipFop instance is for a single hour in the day 24 IncrementalCurve instances where each IncrementalCurve is for a single hour in the day Each IncrementalCurve contains 3 CurveData instances OutputSchedule31000 One OutputSchedule instance One EnergySchedule instance that contains 16 TmPoints PTPObligation6500 One PTPObligation instance One CapacitySchedule instance that contains 16 TmPoints 16 MaximumPrice instances SelfArrangedAS7400 One SelfArrangedAS for a single AsType One CapacitySchedule with 24 TmPoint instances where each TmPoint instance is for a single hour in the day 24 rrs_values instances where each rrs_values instance is for a single hour in the day

16. Lead from the front Texas Nodal http://nodal.ercot.com 16 Average Message Size Estimates (continued) Message Type Average Bid Size (Kb) Estimated Maximum Number of Bids (for 3 Mb Payload limit) Assumptions SelfSchedule31000 One SelfSchedule instance One EnergySchedule instance with 16 TmPoint ThreePartOffer29100 One ThreePartOffer instance 24 EocFipFop instances where each EocFipFop is for a single hour in the day 24 SuMeFipFop instances where each SuMeFipFop is for a single hour in the day 24 StartupCost instances where each StartupCost is for a single hour in the day 24 MinimumEnergy instances where each MinimumEnergy is for a single hour in the day 24 EnergyOfferCurve instances where each EnergyOfferCurve is for a single hour in the day Each EnergyOfferCurve contains 3 CurveData instances

17. Lead from the front Texas Nodal http://nodal.ercot.com 17 Q&A / OPEN FORUM

18. Lead from the front Texas Nodal http://nodal.ercot.com 18 Appendix

19. Lead from the front Texas Nodal http://nodal.ercot.com 19 Nodal Market Activity Update: EDS and Market Activities 2009 (originally presented on 2/6/09) JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 2009 Verifiable Costs Training on NOMCR Open loop test Submission of Verifiable Costs for Resources (different dates for technologies) Resource Registration PUNS Transmission asset registration Telemetry and SE Focused Input Testing (Telemetry and SE) 7x24 ERCOT monitoring FIT w/ SCED begins All QSEs re-qualify DAM submissions Submission Testing SCED & DAM Publish v1.19 Sandbox v1.19 MMS+v1.19+UI+MPIMSCED submissions begin ** Final dates are available in the Integrated Project Schedule Network Model SEM Go-Live Milestone TSP model synchronization TSP MOD training COMS Extracts User Guide release Reporting “Get Reports” available All other RE’s Transmission asset registration QSEs w/ Res SCED re-qualification NDSML and extract supporting documentation updates

20. Lead from the front Texas Nodal http://nodal.ercot.com 20 Standing reports and updates: Nodal API sub-group (originally presented on 2/6/09) TPTF Action – Report, by Transaction, Completion Confidence –Each Transaction will be classified into 3 confidence levels –RED – Confidence low – high risk of change in the 1.18 and/or 1.19 releases –YELLOW – Changes should be limited to non-structural changes (e.g. enumeration changes) –GREEN – Any Changes will be limited to defects. –Note that if there are no changes in 1.18 and significant change in 1.19, a transaction will be marked as RED for both. It will retain that color until all changes are complete.

21. Lead from the front Texas Nodal http://nodal.ercot.com 21 Standing reports and updates: Nodal API sub-group (originally presented on 2/6/09)

22. Lead from the front Texas Nodal http://nodal.ercot.com 22 Standing reports and updates: Nodal API sub-group (originally presented on 2/6/09)