NOTICE DATE:  August 15, 2007

NOTICE TYPE:  W-C081508-01 Operations

CLASSIFICATION: Public

SHORT DESCRIPTION:  Reserve Discount Factor changed for determining
Responsive Reserve Service requirements

INTENDED AUDIENCE:  QSE Operations Personnel

DAY AFFECTED:  August 19, 2008

LONG DESCRIPTION:  The ROS approved an ERCOT proposal that will adjust
the Reserve Discount Factor (RDF) such that additional Responsive
Reserve purchases will not be necessary. 

 

The ERCOT Ancillary Service Methodology links the amount of additional
responsive reserves procured to the day-ahead forecast and the forecast
RDF between 6 a.m. and 10 p.m..  For each hour when the RDF is projected
to be above 2 percent, ERCOT will adjust the day-ahead responsive
reserves upward by 100 MW per percentage point, not to exceed 500 MW.
The ROS approved the ERCOT proposal to reduce the RDF from 7% to 2% for
temperatures greater than 95 degrees Fahrenheit and from 5% to 1% for
temperatures in the range of 85 to 95 degrees Fahrenheit.  Temperatures
less than 85 degrees will reduce the RDF from 4% to 1%. 

 

Beginning August 18, 2008 ERCOT will make the changes to the real-time
RDF and will not purchase additional RRS for Tuesday August 19, 2008. 

Responsive Reserve Service obligation under this change will be
reflected in the regularly scheduled RRS QSE obligation posted by 6 a.m.
for Day Ahead. 

 

ADDITIONAL INFORMATION:  The practice of discounting responsive reserves
was implemented in December 2006, following an analysis of actual
reserves available on April 17, 2006, when rotating outages were
implemented to avoid a system blackout.  (Originally, a 7 percent
discount was applied; in November 2007, it was changed to a variable
discount based on weather zone temperatures.) 

CONTACT:  If you have any questions, please contact your ERCOT Account
Manager. You may also call the general ERCOT Client Services phone
number at (512) 248-3900 or contact ERCOT Client Services via e-mail at
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