Market Trials Open Market Participant Call Weekly Kick Off Sept 20, 2010 http://nodal.ercot.com 1

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. http://nodal.ercot.com 2

This Week’s Activities RTM / LFC Submit Energy Offer Curves representative of a post go-Live scenario Next Full System Market and Reliability Test will begin on 9/28/2010 This test will be 36 hours total Testing times will be confirmed on the Friday Market Call If there are updates to your contacts (especially during the overnight hours, please send those to markettrials@ercot.com. Non-Spin Deployment communications test ERCOT will be conducting a Non-Spin communications test on Thursday 9/23/2010 Test will be conducted in the afternoon Target hour to be communicated to QSE PMs the morning of 9/23/2010 ERCOT will send instructions via the EWS notification process QSEs will update their telemetered Non-Spin schedule based on the test deployment This is a communications test only – Open Loop DAM / RUC DAM, HRUC and DRUC will run daily until the close of Market Trials on 9/30/2010 COPs should continue to be updated based on actual resource status plans (including updates intra day) Exception: see Load Resource Deployment Scenario CRR 09/20/2010: October Auction Credit Locks at 5pm 09/20/2010: October Auction bidding started today 09/22/2010: October Auction bid window closes at 23:59:59 09/23/2010: October Auction second round of bid portfolios in the event of more than 200,000 bids received 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 http://nodal.ercot.com 3

This Week’s Settlements Activities This week’s Operating Days that will be settled 9-21 (DAM Statements and Extracts, RTM Initial Statement Only) 9-22 (DAM Statements and Extracts) 9-23 (DAM Statements and Extracts) 9-24 (DAM Statements and Extracts) 9-25 (DAM Statements and Extracts) RTM Initial Statements for 168 Hour Test will start posting this week http://nodal.ercot.com 4

Load Resources Deployment Scenario Reminders/Updates Next test - Tuesday 9/21 and Wednesday 9/22. This is only a test and there will be no shedding of actual Load. Group 1 and Group Load Resources for RRS” report for Group1/Group2 assignments will be available on the Nodal MIS => Grid => Generation => Load Resource Portlet Reminder sent to QSEs with Load Resources on 9/17. Contact markettrials@ercot.com if you have not received a detailed test script. Test Overview Day 1 – Tuesday 9/21 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 – Wednesday 9/22 0900 Test begins and ERCOT conducts a hotline call. 0915-0945 Group 1 deployed with end time of 11:30 0945-1015 Group 2 deployed with end time of 11:30 0915-1100 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. http://nodal.ercot.com 5

General Updates / Reminder GREDP Results will be distributed late this week Outage Scheduler – New Defect with Copying Outages that already have an actual start date Follow-up from Friday NATF: Trade counts for 9/15 HE 17 730 Confirmed Trades 1460 Created 72 submitting QSEs 99,000 MW represented http://nodal.ercot.com 6