1. May 03, 2007 1 UFE ANALYSIS Old – New Model Comparison Compiled by the Load Profiling Group ERCOT Energy Analysis & Aggregation May 03, 2007

2. 2 UFE Basics Sources of UFE include: ■ Generation Measurement Errors ■ Load - Missing/Erroneous Usage Data - Model Error - Load Profile ID Assignment Error ■ Losses -Model Error - Loss Code Assignment Error  Negative UFE indicates load/losses are overestimated  UFE (unaccounted for energy) is computed as follows: UFE = Generation – (Load + Losses)  UFE % is computed as follows: UFE % = UFE / Generation

3. May 03, 2007 3 UFE Basics Net Generation for Settlement Interval Interval Data Energy Usage Profiled Energy Usage Non-Interval Data Non-Metered Accounts Losses: Transmission & Distribution UFE GAP - - - - - - > Net Generation Compared to Load Buildup

4. May 03, 2007 4 Analysis Overview  Objective: Estimate UFE impact for the 48 new profiles models Analyze UFE impacts on an annual basis and across seasons, day-types and time-of-day  Winter (Dec, Jan, Feb) Spring (Mar, Apr)  Summer (May – Sep) Fall ( Oct, Nov) Analysis based on current profile type assignments Analysis window January 1, 2005 – July 31, 2006 Analysis limited to the most recent settlement run for trade date  Create a dataset of usage-sum values Compute the sum of all meter readings with the same Profile Type, Weather Zone, read start date, and read stop date. Based on usage data available and Profile ID assignments in December 2006

5. May 03, 2007 5  Create daily profile kWh for new and old models by summing the profile intervals for each day of the analysis window  Apply the daily profile kWh values to the usage-sum data to allocate the usage-sum across the days in the meter reading period Result is daily kWh based on new and old profiles Assumed usage records spanning trade days within the analysis window were completely loaded  Apply new and old profiles to the daily kWh to allocate it to intervals within the day  Sum the profiled interval values across all 48 profile type and weather zone combinations for each interval Result is an old and new version of the total profiled load (for the 48 combinations) for each interval Analysis Overview (continued)

6. May 03, 2007 6  Compute the difference between the old and new versions of the total profiled load for each interval Difference = Profiled Load old – Profiled Load new  Add the difference above to UFE (Old UFE) in the interval from the latest settlement run New UFE = Old UFE + Difference All other settlement values thus are held constant Losses were not recalculated … they were also held constant as a simplifying assumption  Proceeded with comparison analysis following the patterns of previous UFE Analysis Reports Analysis Overview (continued)

7. May 03, 2007 7 UFE on Ercot Peak Day August 23, 2005 Old Models vs New Models

8. May 03, 2007 8 UFE MWh by Month New Models vs Old Models UFE │UFE│ Abs. UFE MWh for New Models is 13% lower than Old Models

9. May 03, 2007 9 UFE Cost │UFE Cost│ UFE Cost by Month New Models vs Old Models UFE Cost for New Models is 40% lower than Old Models Abs. UFE Cost for New Models is 19% lower than Old Models

10. May 03, 2007 10 Statistical Comparisons – Study Period New Models vs Old Models

11. May 03, 2007 11 Statistical Comparisons - Monthly New Models vs Old Models

12. May 03, 2007 12 Statistical Comparisons - Monthly New Models vs Old Models

13. May 03, 2007 13 Statistical Comparisons - Monthly New Models vs Old Models

14. May 03, 2007 14 Statistical Comparisons - Monthly New Models vs Old Models

15. May 03, 2007 15 Statistical Comparisons - Monthly New Models vs Old Models

16. May 03, 2007 16 Statistical Comparisons - Monthly New Models vs Old Models

17. May 03, 2007 17 Statistical Comparisons - Monthly New Models vs Old Models

18. May 03, 2007 18 Statistical Comparisons - Monthly New Models vs Old Models

19. May 03, 2007 19 Statistical Comparisons - Monthly New Models vs Old Models

20. May 03, 2007 20 Statistical Comparisons - Monthly New Models vs Old Models

21. May 03, 2007 21 Distribution of UFE MW New Models vs Old Models

22. May 03, 2007 22 Distribution of UFE Cost New Models vs Old Models UFE Cost = ∑(MCPE × UFE_MWh)

23. May 03, 2007 23 UFE % by Day of Week New Models vs Old Models Medians, 5 th and 95 th Percentiles compiled over entire analysis period

24. May 03, 2007 24 UFE % - Average Weekday New Models vs Old Models Medians, 5 th and 95 th Percentiles compiled over entire analysis period

25. May 03, 2007 25 UFE Cost by Day of Week New Models vs Old Models Medians, 5 th and 95 th Percentiles compiled over entire analysis period

26. May 03, 2007 26 UFE Cost - Average Weekday New Models vs Old Models Medians, 5 th and 95 th Percentiles compiled over entire analysis period

27. May 03, 2007 27 UFE % vs Load New Models vs Old Models

28. May 03, 2007 28 UFE % – Average Weekday New Models vs Old Models

29. May 03, 2007 29 UFE Cost vs Load New Models vs Old Models

30. May 03, 2007 30 UFE Cost – Average Weekday New Models vs Old Models

31. May 03, 2007 31 UFE % vs Load by Season New Models vs Old Models

32. May 03, 2007 32 UFE % Average Weekday by Season New Models vs Old Models

33. May 03, 2007 33 UFE Cost vs Load by Season New Models vs Old Models

34. May 03, 2007 34 UFE Cost – Average Weekday by Season New Models vs Old Models

35. May 03, 2007 35 UFE % vs ERCOT Load New Models Medians, 5 th and 95 th Percentiles compiled over entire analysis period

36. May 03, 2007 36 UFE % vs ERCOT Load Old Models Medians, 5 th and 95 th Percentiles compiled over entire analysis period

37. May 03, 2007 37 UFE Cost vs ERCOT Load New Models Medians, 5 th and 95 th Percentiles compiled over entire analysis period

38. May 03, 2007 38 UFE Cost vs ERCOT Load Old Models Medians, 5 th and 95 th Percentiles compiled over entire analysis period