Market Credit Working Group update to the Wholesale Market Subcommittee 05/06/2015 1

MCWG update to WMS Joint meeting of MCWG and CWG on Wednesday, April 22 5 NPRRs reviewed for credit impacts by vote – 4 NPRRs were operational and had no credit impact – 1 NPRR, NPRR690, improves transparency of credit standards 2

MCWG update to WMS Capacity forecast model update Daily posting commenced week of February 24 rd Capacity Forecast Model was run for Operating Days March 3, 2015 through April 8, 2015 with P10, P50, and P90 exceedance confidence intervals Mean model error reduced as model run date gets close to Operating Date As Exceedance Confidence Interval increases, false positives increase failure to predict (false negatives) decrease What is the appropriate confidence interval to use? 3

MCWG update to WMS Consolidation of Other Binding Documents related to credit – Creditworthiness Standards (NPRR690 submitted) – Credit Application (NPRR pending) ERCOT Credit and Legal will jointly draft NPRR – Procedures for Setting Nodal Day Ahead Market (DAM) Credit Requirement Parameters and Credit Formulas (NPRR671) Draft NPRR formalizing prepay account procedures – NPRR702 submitted, targeting May PRS 4

Update on NPRR638 NPRR638 is currently tabled at PRS MCWG/CWG endorsed compromise language on the MAF approval process Technical issues under consideration – ERCOT modeling of NPRR638 & Lookback parameters ERCOT provided modeling results of NPRR638 given varying lookback parameter settings Extreme volatility of credit exposures observed DoD Additional analysis requested CRIM met on 5/1/15 to consider further analysis It appears Lookback mechanism is root cause CRIM will meet again on 5/13/15 to evaluate averaging options 5