SSWG Load Forecast Review
Methodology
Kevin Hanson
RPG Meeting
July 17, 2009
SSWG Load Forecast Review
• The SSWG case is consistently higher than the adjusted
CDR data.
• ERCOT staff has been investigating into the cause of this
difference.
A
B
Description
SSWG (3/12/2009 Case 30)
CDR (May 2009) Coincident Peak
C
D
Private Network in SSWG
Private Network in CDR
9,831
5,244
9,831
5,244
9,831
5,244
9,831
5,244
9,831
5,244
9,831
5,244
4,587
4,587
4,587
4,587
4,587
4,587
68,078
68,643
70,081
71,981
73,986
75,424
5,182
6,784
7,371
7,286
6,922
6,931
7.61%
9.88%
10.52%
10.12%
9.36%
9.19%
E
C-D
Private Network Diff
F
B+E
Adjusted CDR
G
A-F
SSWG to Adjusted CDR Difference
H
A / F - 1 SSWG to Adjusted CDR ratio
July 17, 2009
2009
73,260
63,491
2010
75,427
64,056
2011
77,452
65,494
2012
79,267
67,394
2013
80,908
69,399
2014
82,355
70,837
2
RPG Meeting
Current Data Available
• ERCOT staff has looked at multiple data sources available
to investigate what is contributing to this difference.
– FERC 714 (data from 1993 to 2000)
• Control Area NCP
• Control Area load at ERCOT CP
– ALDR report (data from 2001 to 2008)
• Bus level NCP (excluding losses and UFE)
• Bus level load during ERCOT system CP (excluding losses and
UFE)
– Market settlements (2004 to 2008):
• TDSP NCP (including losses and UFE)
• TDSP load at ERCOT CP (including losses and UFE)
July 17, 2009
3
RPG Meeting
Possible Reasons – One year bump in loads (2008 to 2009)
• One year increase in total coincident peak for the seven
largest TSPs in approximately 5,400 MW
• There exists an argument of 2007 and 2008 being relatively
cool which justifies bump
• If you assume 2006 to 2009 annual average growth rate of
2%, load for these seven TSPs would only increase
approximately 3,300 MW while the underlying ALDR data
increases approximately 5,200 MW for that same time
period (difference of 1,900 MW)
• One year bumps also occurred in the 2007 and 2008
ALDRs
July 17, 2009
4
RPG Meeting
Possible Reasons – Load forecasts from 2009 to 2015
• The seven largest TSPs’ aggregate load forecasts increase
2.15%
• Two of these seven TSPs’ coincident peak forecasts is above
4.50%
• If these 2 market participants coincident peak forecasts
were only 2%, their combined load forecast by 2015 would
be reduced approximately 2,300 MW
July 17, 2009
5
RPG Meeting
Possible Reasons – Non-coincident peak ratio
• ALDR data (bus level NCP) from 2001 to 2008 shows
about 7.6% non-coincident to coincident peak ratio
• Market settlement NCP to CP (TDSP NCP) ratio from
2004 to 2008 is 3.60%
• The NCP to CP ratio is 4.30% from 2009 to 2015 in the
ALDR data which is bus level NCP
• The 0.7% difference is probably about a 500 to 600 MW
impact
July 17, 2009
6
RPG Meeting
Summary
• Multiple TDSPs are assuming much larger CP load growth over
the next 7 years (13,300 MW) than existed the past 8 years
(5,300 MW)
• ERCOT is attempting to understand the load forecasting
process utilized by the TDSPs
• We are trying to develop understanding of any inconsistencies in
the levels of load included by each TDSP and we have talked to
some already.
• Is the one year bump up too high from 2008 to 2009 when 2009
is in a recession; is it even driven by economic or something
else?
• What level of coincidence consistency should be used? Bus level,
TDSP level, or ERCOT coincident peak?
• Looking at the historical data, is the load forecast too high?
July 17, 2009
7
RPG Meeting
Questions?
July 17, 2009
8
RPG Meeting