1. GATF Loss of Load Process (or How to Make Sausage) October, 2012

2. 2 Timeline from April GATF Meeting (and revised schedule) ITEM RFP released Contract issued to ECCO International Expected date of draft results Expected date of final report Revised date of draft results Revised date of final report DATES October 2011 January 2012 July 2012 August 2012 November/December 2012 December 2012 / January 2013

3. 3 Step by Step Process Collect ingredients Feed into analytic blender –2010 study used internal single node MatLab model –2012 study has outsourced the study to Ecco International –Calculate Effective Load Carrying Capability (ELCC) of wind generation resources by location –Calculate Target Reserve Margin (TRM) Write report summarizing results Should be easy right?!? Hard part is getting the right ingredients

4. 4 Ingredients Outage Data (Source: GADS or from Generator) Hourly Load Shapes (Source: ERCOT Load Forecasting Team) Hourly Wind Shapes by Unit (Source: AWS TruePower) Generator Data (e.g. Monthly Capability) (Source: ERCOT)

5. 5 Outage Data Specific Outage data is NOT available for all units Some unit data came from GADS data –It was not mandatory for generators to collect this data until January 2012 for GADS Some unit data came directly from generators –Not all data received from generators was usable It took 3 months to collect this data –January 2012 to April 2012 Missing data was filled in by ERCOT generic assumptions based on class type and size using averages from GADS data Other ISOs require their generators to deliver this data to participate in the their markets

6. 6 Hourly Load Shapes 15 years of hourly load shapes were obtained from ERCOT’s load forecasting department 1997 to 2011 weather years Based on Moody’s base economic forecast for 2014 and 2016 5 years of weather data was used for studies –2011 (Extreme summer weather) –2010 (Warmer than average) –2006 (Average weather) –2008 (Cooler than average) –2004 (Much cooler than average) Private Use Network (PUNs) load included from SSWG datasets October, 2012

7. 7 Hourly Wind Shapes ERCOT staff received the initial wind shapes from AWS data in middle of May 2012 Data was delivered to Ecco Ecco delivered initial results end of August ERCOT analyzed results and questioned their accuracy –Existing resources were being modeled with new technologies ERCOT received new wind shapes from AWS end of September –Currently reviewing and comparing to actual output to add “reality” test to analysis

8. 8 Generator Data Data pulled from RARF and SSWG datasets data Used mothballed units which are greater than 100 MWs –Valley 1 to 3 –Permian Basin 6 –Green Bayou 5 Added 11,500 MW generic resources at existing locations with available transmission –Added to capture the entire range of LOLEv results for each of the different load profiles PUNs generation included Hydroelectric generation not included DC Ties not included October, 2012

9. 9 QUESTIONS / COMMENTS??? October, 2012