1. http://nodal.ercot.com 1 Market Trials Open Market Participant Call Weekly Kick Off Sept 27, 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 This Week’s Activities RTM / LFC –Submit Energy Offer Curves representative of a post go-Live scenario –Full System Market and Reliability Test will begin on 9/29/2010 8am and end 9/30/2010 8pm Note that ERCOT Grid Operations may change testing times due to system conditions at any time This test will be 36 hours total Market Notice will confirm test go ahead 2 hours prior to test start Note that this test will include a Network Model load at midnight on 9/30/2010 If there are updates to your contacts (especially during the overnight hours, please send those to markettrials@ercot.com). markettrials@ercot.com DAM / RUC –DAM, HRUC and DRUC will continue through 9/30 (last operating day 10/1/2010) –COPs should continue to be updated based on actual resource status plans (including updates intra day) Exception to Load resources noted on next slide –System Wide Offer Cap will remain at max $180 (or 18 times FIP) –System Wide Offer Floor will remain at -$50 CRR –09/27/2010: October Monthly Auction Results Posted –09/28/2010: October Monthly Auction Invoice to be distributed Outage Scheduler –Maintain outages for remainder of September and post Go-Live –Those who have not sent in confirmation of post Go-Live verification and synchronization, please continue to work on this

4. Load Resources Deployment Scenario http://nodal.ercot.com 4 Test Results Test #1 – 55 Load Resources with test deployments of 316 MW Test #2 – 94 Load Resources with test deployments of 852 MW Issue identified when Group 2 LRs are deployed. A recall message of 0 MWs is sent to Group 1 LRs. Until the issue is corrected, ERCOT will deploy Group 1 and Group 2 LRs together, so that no inadvertent 0 MW recall messages are sent to Market Participants. Reminders/Updates Next test – Monday 9/27 and Tuesday 9/28. This is an open-loop test. There will be no shedding of actual Load. Test Overview Day 1 – Monday 9/27 QSEs update their Load Resource COPs to reflect self arranged schedules and awards from DAM prior to DRUC (DRUC starts at 1430) After DRUC completes, ERCOT creates Group 1 & Group 2 deployment stacks and publishes the report to the MIS Secure Area Day 2 – Tuesday 9/28 0900 Test begins and ERCOT conducts a hotline call. 0945-1000 Group 1 deployed with end time of 11:30 1015-1030 Group 2 deployed with end time of 11:30 0945-1100 QSEs adjust their telemetered RRS Schedules. 1100-1115 ERCOT recalls the deployment 1115-1200 ERCOT issues a VDI to confirm schedules have been adjusted to return to service.

5. http://nodal.ercot.com 5 This Week’s Settlements Postings This is the last week that Settlements Statements, Invoices and Extracts will be posted

6. http://nodal.ercot.com 6 Known Issues Recently Opened Known Issues Non-Spin Deployments- The Operator display that is used to deploy non-spin does not consider the COP responsibilities from all possible Combined Cycle configurations that will be operating in the next operating hour NP6-905-CD, Settlement Point Prices at Resource Nodes, Hubs and Load Zones (MIS Public) Report is not being posted when SCED does not run, although SPP reports are generated in MMS every 15 minutes whether or not SCED runs Requires modification of event trigger that generates the report Affects CDR Modifying Telemetry Reports to reflect new TAC-approved Telemetry Standard NP8-146-ER Critically Important Telemetry Availability Report NP8-365-ER Monthly Telemetry Point Availability Statistics Report NP8-475-ER Quarterly Telemetry Point Availability Statistics Report NP3-129-CD: Daily Competitive Constraints (MIS Secure) Competitive Constraints reports pulled from EWS are not pulling the Contingency Name file, causing some of the report data to look like duplicates

7. http://nodal.ercot.com 7 Known Issues Recently Closed Known Issues NP6-788 LMPs by Resource Nodes, Load Zones and Trading Hubs SCED timestamp was previously not being included for the retry reports Affected CDR MIS Data Classification on Portlet banners The data classification for the Portlet banners on MIS was not previously being included on all landing pages Affected the Portal Builder LMP and SPP Reports The retry reports for LMPs/SPPs was not previously producing postings for the correct missed intervals Affected CDR NP4-731-SG: Wind Generation Resource Power Potential Forecast (MIS Certified Report)- The “Resource” column was previously being populated with a site-level name attribute rather than a unit-level name Affected the AWS application

8. http://nodal.ercot.com 8 Known Issues Recently Closed Known Issues NP3-129-CD: Daily Competitive Constraints Duplicate records were previously being passed to the DCC report from the monthly CCT file that is used to build the report. Duplicates were identified in some of the July and August 2010 reports. A uniqeness check has been built into the process that grooms the monthly file, so no duplicates should be seen in the Daily Competitive Constraints file starting September 4, 2010 moving forward. Change of LDL calculation in RLC There was previously an issue that was observed during the LFC test on 8/20/2010 in which an ICCP error caused HSL to be set equal to LSL for a majority of a QSEs Resources, resulting in Base Points that ignored the ramp rates for the resources. To resolve this issues, ERCOT wrote an NPRR to remove some of the protocol language that was added as part of the NPRR 119 to allow changes in LDL calculation that will result in Resources always being sent Base Points that will ramp them to their HSL when it changes rather than setting the Base Points equal to the new HSL. Affected EMS RLC

9. Standing Reports and Updates: General Reminders / Updates http://nodal.ercot.com 9 Reminders/Updates Updates to Tracking Artifacts The updated Known Issues tracking sheet is available on the Readiness center at http://nodal.ercot.com/readiness/markettrials/rtm/index.html\http://nodal.ercot.com/readiness/markettrials/rtm/index.html\

10. http://nodal.ercot.com 10 State Estimator Convergence Update State Estimator Daily Convergence Statistics (these percentages are graphed in the next slide) MonthDay% Convergence (Including Solved w/ Mismatch) SEPT1398.98% SEPT14100.00% SEPT1596.47% SEPT1689.86% SEPT1794.64% SEPT1885.19% SEPT1986.36% SEPT2098.63% SEPT21100.00% SEPT2299.65% SEPT2394.59%

11. http://nodal.ercot.com 11 State Estimator Convergence Update