1. http://nodal.ercot.com 1 Market Trials DAM/RUC/SASM Weekly Update May 21, 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 DAM/ RUC/SASM summary QSE Activities for Next Week General Reminders/Updates Environment Report –Outages –Known Issues Special Topics –JOUs –Fixed AS Offers (Load Resources) Question and Answers / General Discussion Appendix 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 SASM Overview for May 14 SASM overview SASM market was opened at 2:59 pm for the reason ‘Increased AS Plan’ for Hours 19-22 (100 MW RegUp, 100 MW RegDn, 200 MW RRS, and 150 MW of NSRS in each hour.) No self-arrangement was submitted, so the total amount of the increased AS Plan was procured from existing unexpired AS Offers

6. http://nodal.ercot.com 6 HRUC Overview for May 14 HRUC overview ERCOT ran HRUC on May 14 at 9 am and made 45 Resource commitments. Similar results to the DRUC for the same Operating Day that we discussed on last week’s call. –Number of issues created solution that was not operationally approved

7. http://nodal.ercot.com 7 Submission Overview for May 18 DAM submission overview 200 QSEs participated for Op Day 5/19 Cleared 19,751 - 25,248 MW per hour Four major Load Zone prices ranged from $23.31 to $49.78

8. http://nodal.ercot.com 8 Submission Overview for May 18

9. http://nodal.ercot.com 9 DRUC Overview for May 18 DRUC overview Published 94 Resource commitments. Not operationally approved based on operator experience. Results were published to exercise market and ERCOT downstream systems (as described last week) RUC clearing engine software results were consistent with input data Status update on these issues will be discussed later

10. http://nodal.ercot.com 10 HRUC Overview for May 19 HRUC overview ERCOT ran HRUC on May 19 at 4 pm and made 59 Resource commitments. –Similar results to the DRUC for the same Operating Day

11. http://nodal.ercot.com 11 Submission Overview for May 19 Submission overview 180 QSEs participated for Op Day 5/20 Cleared 23,453 – 32,738 MW per hour Four major Load Zone prices ranged from $19.72 to $39.86.

12. http://nodal.ercot.com 12 Submission Overview for May 19

13. http://nodal.ercot.com 13 DRUC Execution Overview for May 19 DRUC execution overview: 126 Resources committed for Operating Day May 20 Not operationally approved based on operator experience. Results were published to exercise market and ERCOT downstream systems (as described last week) RUC clearing engine software results were consistent with input data Status update on these known issues will be discussed later

14. http://nodal.ercot.com 14 HRUC Overview for May 20 HRUC overview ERCOT ran HRUC on May 20 at 4 pm and made 48 Resource commitments. –Similar results to the DRUC for the same Operating Day

15. http://nodal.ercot.com 15 Submission Overview for May 20 Submission overview 194 QSEs participated for Op Day 5/21 Cleared 27,120 - 39,990 MW per hour Four major Load Zone prices ranged from $22.22 to $45.01.

16. http://nodal.ercot.com 16 Submission Overview for May 20

17. http://nodal.ercot.com 17 DRUC Execution Overview for May 20 DRUC execution overview: 90 Resources committed for Operating Day May 21 Not operationally approved based on operator experience. Results were published to exercise market and ERCOT downstream systems (as described last week) RUC clearing engine software results were consistent with input data Status update on these known issues will be discussed later Reminder that ERCOT running HRUC today as planned for Operating Day 5/21 – results will be discussed on next week’s call.

18. http://nodal.ercot.com 18 RUC Execution Overview for the week RUC Summary for the week: ERCOT issues –Known issue regarding outages that close breakers –Phase shifters are not modeled in MMS Work around is to change transformer parameters to operations value in the database –Constraint issue for CCs in a mustrun mode for the whole study period and is has an up transition Max daily startup constraint error when CC is ON in a mustrun mode. No commitment decision needs to be made, but the software is modeling the temporal constraints. The effect is that the constraint is applied and uses a decision variable only defined for a cycling CC which causes an optimization error. COP submission issues –Configurations that were OFF but could not be started because all the startup configurations were OUT –CC configuration LSL greater than aggregated step-up transformer rating –Multiple configurations ON –JOU resource statuses are not consistent or no COP submitted for one owner (considered OUT) –Inconsistency with zonal resource plan –COPs with HSL = 0

19. http://nodal.ercot.com 19 Next Week’s Activities Next week – Op Days are 5/25-5/29 DAM executing on 5/24-5/28 DAM moving to 5 x week No guardrails anymore, beginning this week –Bids/offers should be reasonable –We will continue to evaluate for potential AS insufficiency and reduce the AS Plan prior to clearing if necessary to avoid an AS insufficiency COPs should reflect zonal throughout the week. We are requesting no COP updates as a result of nodal market processes. Week 4 Note: Dates are DAM execution days 5/24/2010 - 5/28/2010 Objective Ramp to 5x week Network Constraints Included DAM 5 x week Self-Arranged AS Requested Actual Load Bid MW Requested Restrained based on OLA only Virtual Bids / Offers Restrained based on OLA only PTP Obligations Restrained based on OLA only NOIE CRR Offers Any COP Updates Reflect zonal DRUC W/ each DAM HRUC Limited SASM As needed

20. http://nodal.ercot.com 20 Next Week’s Activities DRUC executing on 5/24-5/28 after DAM HRUC and SASM executing on 5/25-5/28 HRUC and SASM –HRUC will be executed on Tuesday, Wednesday, Thursday and Friday at 1 pm (target Operating Hours will be the balance of the Op Day) –SASM will be opened if needed based on system conditions Week 4 Note: Dates are DAM execution days 5/24/2010 - 5/28/2010 Objective Ramp to 5x week Network Constraints Included DAM 5 x week Self-Arranged AS Requested Actual Load Bid MW Requested Restrained based on OLA only Virtual Bids / Offers Restrained based on OLA only PTP Obligations Restrained based on OLA only NOIE CRR Offers Any COP Updates Reflect zonal DRUC W/ each DAM HRUC Limited SASM As needed

21. http://nodal.ercot.com 21 Next Week’s Activities Next week Reminder that we transfer zonal outages to nodal every week on Monday –This transfer represents approximately 85% of the actual zonal outages Again, next week ERCOT may do workarounds outside the normal business process to sidestep any issues that arise. Furthermore, we may approve the results of the RUC software even if the result is operationally unreasonable. The purpose of this is to exercise settlement and billing determinants related to RUC. Week 4 Note: Dates are DAM execution days 5/24/2010 - 5/28/2010 Objective Ramp to 5x week Network Constraints Included DAM 5 x week Self-Arranged AS Requested Actual Load Bid MW Requested Restrained based on OLA only Virtual Bids / Offers Restrained based on OLA only PTP Obligations Restrained based on OLA only NOIE CRR Offers Any COP Updates Reflect zonal DRUC W/ each DAM HRUC Limited SASM As needed

22. http://nodal.ercot.com 22 General Reminders/Updates Network Model Update –Last data load was 5/19 –An updated settlement points and MP short name list was posted for the 5/19 load at http://nodal.ercot.com/readiness/markettrials/index.htmlhttp://nodal.ercot.com/readiness/markettrials/index.html –Next scheduled load is 5/24

23. http://nodal.ercot.com 23 General Reminders/Updates Changed the credit data this week Please note that on Tuesday ERCOT adjusted the data that is used to evaluate energy offers for credit purposes in the day-ahead. –All price differences between real-time and day-ahead greater than $20 were reduced to $20. –Note that this data is only used for purposes of calculating the credit exposure for energy offers, and the historical prices themselves are not being adjusted. –Three-Part Offers have been consuming a lot of credit recently and this data change served to reduce that consumption markedly, effective for the Phase 2 validation process that ran for Operating Day 5/20. –This was done again on Thursday –We may need to do this periodically but the need for it should be reduced as we go to DAM 5 x week ERCOT still using the original credit exposure calculation that existed prior to NPRR206, which has not yet been implemented. The rule when evaluating energy offers for credit is: Quantity of the offer times the 95th percentile of the hourly difference between the RT SPP and the DAM SPP over the previous 30 days. –SCED has seen many intervals at the system-wide offer cap and beyond due to a lack of offer curves in the system over the last 30 –Also, because ERCOT has only been running DAM 2 x week, over the previous 30 days there is not 30 days of data. This causes the 95th percentile to be the highest price differences (more data would have diluted the effect of the high SCED prices).

24. http://nodal.ercot.com 24 Support Metrics * This week, 23 out of 375 questions were responded to outside of the 24 hour time frame. Market Participant Inbound Questions

25. http://nodal.ercot.com 25 Day-to-day operations summary: Planned / Unplanned Outages Outages Planned Outages –N/A Unplanned Outages –05/15/2010 02:05 A.M. – 05/15/2010 05:05 A.M. Performance degradation with SCED processes were noted during the reported time period. The root cause has been identified to a system backup being executed around same time frame.

26. Environment Report-Known Issues Full DAM/RUC/SASM known issues list will post every Friday night at http://nodal.ercot.com/readiness/markettrials/dam/index.html http://nodal.ercot.com/readiness/markettrials/dam/index.html New issue (already resolved) QSE-entered Resource Parameters are getting purged after 7 days. This causes the system to use the RARF parameters. This data is not supposed to be purged and this issue is being fixed today. Resource Parameters remain until cancelled by the QSE. –[Helpful tip: Be sure to change the Reason box when submitting a Resource Parameter transaction.] New DAM/RUC/SASM known issues If a full TPO is submitted for some hours of an Operating Day, and an EOC-only (no startup/minimum energy costs) is submitted for other hours of the same Operating Day, the query cannot be returned http://nodal.ercot.com 26

27. Environment Report-Known Issues Closed DAM/RUC/SASM known issues DAM clearing software cannot currently handle certain combinations of decimals in subroutines process Special scenario created with outage data caused a split network http://nodal.ercot.com 27

28. Environment Report-Known Issues New MIS known issues The two reports that were enabled this week are currently experiencing posting issues and are delayed –NP5-751-CD, Daily RUC Committed or Decommitted Resources –NP5-752-CD, Hourly RUC Committed or Decommitted Resources http://nodal.ercot.com 28

29. Environment Report-Known Issues Status update of recurring DAM/RUC software issues: Bid/IDs with special characters issue –Validation rule added in External Interfaces Specification v1.19L, scheduled 5/28 –Please avoid these in your submission until then Outage issue with regard to closed breakers –Potential fix identified, delivery date late June –We are still evaluating possible workarounds Data issues are also currently being worked by ERCOT teams to correct –Model load on 5/19 fixed some data issues –COPs will continue to focus on zonal operations –Continuing to look at other data issues with line ratings, load distribution factors, breaker statuses http://nodal.ercot.com 29

30. Special Topic – Jointly Owned Units JOUs are modeled as a single physical unit –DAM uses the separate logical resources when evaluating energy and ancillary services, but Network Security Monitoring (NSM), which is a sub-process of DAM, must consider the physical unit. –http://nodal.ercot.com/docs/pd/ida/wp/sgrm/IDA041_White_Paper_for_Split_Generation_Resource_M odeling_v1.dochttp://nodal.ercot.com/docs/pd/ida/wp/sgrm/IDA041_White_Paper_for_Split_Generation_Resource_M odeling_v1.doc JOUs offering into DAM –Owners offer their share into the DAM separately, but the physical unit must be committed together –All owners have to offer in the unit (energy or AS) to the DAM or else it cannot be committed to any owner (one exception for a self-commitment scenario described below). DAM must make a commitment decision about the physical unit, which it cannot do without offers from all the owners. –Self-commitment examples (assume three owners) – remember that self-committing by submitting Startup and Minimum Energy Costs as ‘NULL’ (leaving them out of the submission altogether rather than submitting zeroes) signals the DAM software that it doesn’t need to make a commitment decision and to ignore resource constraints. If two owners self-commit (startup/minimum energy costs are NULL) and the other submits nothing, the unit can be awarded without making a commitment decision. If one owner self-commits, another submits a TPO with startup/minimum energy costs, and the third submits nothing, the unit cannot be awarded If one owner self-commits, and the other two submit TPOs with startup/minimum energy costs, the unit can be awarded after making a commitment decision based on the resource constraints and the submitted startup/minimum energy costs. –Note that if self-committed, do not submit an OFFNS offer. That offer negates the self-commitment and the DAM software will not consider it as a self-committed resource (since the QSE is requesting ERCOT to evaluate the unit offline) http://nodal.ercot.com 30

31. Special Topic – Jointly Owned Units JOUs and COP consistencies In DAM, if the different owners of the jointly-owned unit have submitted conflicting COP statuses for the current day, online statuses will overwrite offline statuses when DAM is determining the initial condition of the unit (i.e., is the unit online or offline at the start of the next operating day). In RUC, if the different owners have conflicting COP statuses for the next operating day: –If any owner has OUT status for any hour then the unit is considered OUT. –If all owners have submitted a COP, and at least one of them has an online status in a particular hour then the resource status for the unit is online (unless any owner has OUT) Owners should keep COPs consistent with regards to resource status. ERCOT sends an hourly notification to let the owners know if there is an inconsistency for a particular hour Different ONLINE COP statuses are fine (e.g., one owner has ON and one has ONOS). –Note that a known issue is currently causing ERCOT to send notifications to JOUs when there is an online resource status conflict http://nodal.ercot.com 31

32. Special Topic – Fixed AS Offers (Load Resources) Fixed AS Offers (for Load Resources) Care should be taken to not submit fixed-quantity block AS Offers for Load Resources where the fixed-quantity exceeds the HSL in the COP. Example: –An RRS offer with a fixed-quantity block of 20 MW means that DAM has to award all 20 MW or none. –If the COP for the next Operating Day shows that the HSL is 15 MW, the AS Offers cannot be awarded, since DAM can only award 20 MW. DAM must respect the constraints in the COP for the next day. –If the offer had been ‘variable’ rather than ‘fixed’, up to 15 MW could be awarded. http://nodal.ercot.com 32

33. Summary of DAM/RUC/SASM market trials Past few weeks of trials for DAM/DRUC/HRUC/SASM have had the objectives of ramping-up: -Ensuring connectivity and successful communications with markets (bids/offers/awards) -Exercising the mechanics of markets based on operational and market data -Responding to market questions on clearing behavior (hundreds of emails) -Tuning of software At this point no significant core application issues have been discovered (i.e., clearing engines and optimizations) ERCOT is transitioning to focus on quality of solution. To do so…. -ERCOT is focusing on operational data (breaker status, load distribution factors, ratings, RARF data, TSP data) -Need MPs to focus on realistic Resource data (zonal resource plans = COPs) and Resource Offers (start-up costs) -ERCOT is developing tools/scripts to measure and report data quality and solution What will change? -Focus on quality will supersede timelines (i.e., may re-run DAM/RUC late to get better solution) -In short-term need COPs to reflect actual plans (to compare with zonal) -More communication between ERCOT and MPs to address submission/data issues -This call will start to transition from reporting results to reporting issues and resolution path http://nodal.ercot.com 33

34. http://nodal.ercot.com 34 Q&A Q&A / Open Forum

35. Appendix –Pre- and post-DAM reports –Special Topics http://nodal.ercot.com 35

36. Other Note: All transactions will be supported. Trade submission and confirmation (Energy, Capacity and AS Trades) may be exercised at this time. DAM notifications will be active. Phase 2 Validation process will be active and supported. QSE transactions that do not follow the guidelines are subject to cancellation at ERCOT’s discretion. ERCOT may run DAM on non-supported days. No QSE participation is requested, and ERCOT staff will not be available to answer questions regarding the outputs of these non-supported processes. CRR information from the market trials auction will be integrated into the market system. CRR Offers (by NOIEs) must contain CRR IDs from this auction in order to be valid. http://nodal.ercot.com 36

37. Supplemental Materials Slide 37 Reference and DescriptionLocationVersion External Interfaces Specification http://nodal.ercot.com/readiness/sandbox/index.html1.19 Explanation of Market Submission Items http://nodal.ercot.com/readiness/markettrials/connectivity/in dex.html 0.26 Market Manager User Guidehttp://nodal.ercot.com/readiness/markettrials/connectivity/in dex.html 0.06 MMS Requirementshttp://nodal.ercot.com/docs/pd/mms/index.html#reqVarious Market Connectivity Handbookhttp://nodal.ercot.com/readiness/markettrials/connectivity/in dex.html 0.97 DAM/RUC Known Issues Listhttp://nodal.ercot.com/readiness/markettrials/dam/index.ht ml N/A Web Services XSDshttp://nodal.ercot.com/readiness/sandbox/index.html1.3.19 Sample Reports, Extracts, and DDLs http://nodal.ercot.com/readiness/reports/index.htmlVarious DAM ERCOT Operating Procedures http://nodal.ercot.com/readiness/markettrials/dam/index.ht ml 2.0 DRUC/WRUC ERCOT Operating Procedures http://nodal.ercot.com/readiness/markettrials/dam/index.ht ml 0.2 http://nodal.ercot.com 37

38. http://nodal.ercot.com 38 Report Postings Posted by 6 am: Ancillary Services (AS) Plan Load Ratio Shares (these will be static based on Zonal production data as of October 16, 2009) * AS Obligations * Wind Generation Resource Power Potential (WGRPP) forecast * and Aggregated WGRPP forecast List of all Settlement Points and the mapping to Electrical Buses Load forecasts for ERCOT system, Weather Zones and Load Zones Load forecast distribution factors Distribution Loss Factors and forecasted Transmission Loss Factors Weather assumptions * Denotes MIS Certified reports

39. http://nodal.ercot.com 39 Report Postings Posted after each DAM: Awards (AS Offers, Energy Offers, DAM Energy-Only Offers, DAM Energy Bids, CRR Offers, and PTP Obligation Bids) * DAM Clearing Price for Ancillary Services (MCPC) Day-Ahead hourly Settlement Point Prices (SPPs) Day-Ahead hourly Locational Marginal Prices (LMPs) Shadow Prices Quantity of AS Offers Aggregated AS Offer Curve Total quantity of energy (in MWh) bought and sold in DAM See DAM Handbook for a list of all DAM/RUC/SASM reports available starting in Phase 4.0 - http://nodal.ercot.com/readiness/markettrials/dam/index.html. See MIS Handbook for a comprehensive list of reports available - http://nodal.ercot.com/readiness/markettrials/mis/index.html.http://nodal.ercot.com/readiness/markettrials/dam/index.html http://nodal.ercot.com/readiness/markettrials/mis/index.html * Denotes MIS Certified reports

40. Special Topics Phase 2 Validation reports and process Phase 2 validation re-evaluates all submitted transactions at 7 am in the day-ahead with updated information, such as AS Obligation, CRR ownership, credit limits, etc. If there is a validation error, ERCOT will cancel the transaction We send a notification that a Phase 2 report is available for a particular transactions type, and notification containing the cancellation for the transaction. You can query for the Phase 2 report via web service or on the Reports page of the Market Manager in order to view the reason for the cancellation. Correct and resubmit prior to 10 am. Note that submissions are locked out during the Phase 2 process, which is currently taking about 15 minutes to complete. http://nodal.ercot.com 40

41. Special Topics Day-Ahead Self Commitment DAM clearing engine treats your TPO differently if you submit Startup and Minimum Energy (SU/ME) costs as $0 vs. NULL If you submit with SU/ME as $0, DAM engine treats this as a normal offer where the QSE is not requesting SU/ME to be covered. HSL/LSL constraints will be respected. Also, if you are selected for an online Ancillary Service, you will also be awarded at least LSL on your offer curve. If you submit with SU/ME as NULL, DAM engine is signaled to ignore the HSL/LSL constraints for the resource. In this scenario, the offer curve submitted will start at 0 MW and go to the max MW quantity desired – again, DAM will ignore LSL/HSL constraints. If the offer curve submitted doesn’t start at 0 MW, it will be extended to 0 MW by DAM. If the resource is selected for Ancillary Services, no requirement to also award TPO at LSL (since no LSL constraint honored in this case). http://nodal.ercot.com 41

42. Special Topics Day-Ahead Self Commitment The purpose of the NULL: It allows a QSE to use part of a Resource to serve its own load, and then offer in the rest to the DAM and enable the offer to be co- optimized with its AS Offer. Example: A Resource has 100 MW LSL and 400 MW HSL, and the QSE has already committed 300 MW of the Resource through some other mechanism. The QSE wishes to offer the remaining 100 MW, which would otherwise be ignored due to the 100 MW LSL. Then going into real-time, so QSEs will need to update their TPO to cover the full capacity of the resource, from LSL to HSL, rather than from 0 MW. To do that if the resource is awarded in the DAM, the QSE must provide a reason code, which is DSCM. This functionality came about due to TPTF subgroup on the issue. It has not yet been added to the protocols but will during our protocol traceability/cleanup effort. http://nodal.ercot.com 42

43. Special Topics Bid/Offer efficiencies ERCOT has identified efficiencies in Bid/Offers submission with regard to the format of submission This applies to all transaction that use a Bid ID or an Offer ID (Energy Only Offers, Energy Only Bids, PTP Obligation Bids, and CRR Offers) Preference is for QSEs to submit the same Bid/Offer ID for each hour in the submission, versus submitting a different Bid/Offer ID for every hour. The market system treats the submission the exact same way, regardless of which format is used Using the preferred format will optimize DAM system performance For xml examples detailing this issue, please view a document that will be posted along with this presentation on the calendar page at http://www.ercot.com/calendar/2010/04/20100409-MT http://www.ercot.com/calendar/2010/04/20100409-MT This was discussed at NATF 4/6, we send an email to the nodal technical contacts that we have on file for all QSEs, and we will add it to the External Interfaces Specification http://nodal.ercot.com 43

44. Special Topics JOUs and COP consistencies In DAM, if the different owners of the jointly-owned unit have submitted conflicting COP statuses for the current day, online statuses will overwrite offline statuses when DAM is determining the initial condition of the unit (i.e., is the unit online or offline at the start of the next operating day). In RUC, if the different owners have conflicting COP statuses for the next operating day: –If any owner has OUT status for any hour then the unit is considered OUT. –If all owners have submitted a COP, and at least one of them has an online status in a particular hour then the resource status for the unit is online (unless any owner has OUT) http://nodal.ercot.com 44