QMWG 10/7/13 Generation Resource Energy and Regulation Deployment Performance

2 GREDP –NON-WIND Summary Conventional Resources - September –311/312 scored above 90% 1 failure SCGT90 Scored ½ hour for the month of September with average error of 2 MW. Non-wind resources scoring >85% in previous summer months were resources with very low Capacity Factors August /319 July 307/308 June313/315 May287/292

3 CONTROL PERFORMANCE (September) CPS1(167) trending favorably –Consistently scoring 160+ this summer –Slightly lower than July and August 2013 CPS2 (98.84) has improved from 2012 –August performance particularly impressive (99+) ½ of the days perfect score 2012 CPS2 trended very positively Passed 2012 CPS2 (ERCOT Waiver) Other ISO CPS2 performance declined over the same period –Other Improvements observed –Ramping periods RMS1 decreased Startup/shutdown improved performance –Overall RMS1 declining in 2013 Up slightly in September from August

4 WIND AND RENEWABLES Summer 2013 Scoring consistent/above previous years in the summer –Reduced congestion (Slide 7) with similar or increased Energy from Wind (Slide 5) and GREDP scores SEPT 2013 –58 scored/21exceeded 95% GREDP Monthly –2,250 intervals scored, 1,950 intervals passed (86.5%) –July & August intervals ↓ sharply (slide 6) –3 resources 100+ intervals/>95%: 94%(112), 71% (115), 92%(142) –Recent analysis indicates a very positive trend from previous summers. Significant issues reduced/mitigated Recent months indicate resources line up with technology

5 Wind Energy Ratios and Totals Total Energy (GWH) % Wind Energy INTERVALS SCORED MAY 20112, %39, ,6009%19, , %7,600 June 20113, %46, , %9, , %4,000 July 20111, %2, , %1, , %283

6 Congestion Management Congestion in wind areas has dropped off in 2013 –CREZ lines energized earlier in summer –Reduction in intervals scored No reported or observed issues regarding Congestion Management. –No Inter-zonal Interface limit issues in West No issues in Q2 or Q One instance in Q1 –Forced outage initiated a unit-step drop in the west-north flowgate –Immediately resolved by Wind redispatch

7 Summer IRR GREDP Summary and Congestion Trends MayJuneJuly Average GREDP91%83%94% Scored Scored < 95%43345 DEVIATION Ave rage INTERVALS7,6004, PASSED7,0003, >100 intervals294535