ERCOT2003 UFE ANALYSIS

By William Boswell & Carl Raish

AEIC Load Research Conference July 13, 2005

TDSP Metered Entities

ERCOT Polled

Settlement Meters

Corrected CR Load

Generation Data

Calculate and

Allocate UFE

CR Load

Data Aggregation Process

Registration Data Settlement

Retail Load Data

Aggregation

Gen/Zonal Data

Aggregated CR/NOIE Load

Generation & Zonal

Meter Data Aggregation

NOIE Data

Apply T&D Losses NOIE

Load

Profiling

Data Acquisition

ERCOT MV90

System

TDSP Data

Collection Systems

ERCOT SETTLEMENT PROCESS

CURRENT PROFILE GROUPS AND SEGMENTS

•Residential Low Winter Ratio

•Residential High Winter Ratio

•Business Non-Demand

•Business Low Load Factor (< 40%)

•Business Medium Load Factor (40% - 60%)

•Business High Load Factor (> 60%)

•Business IDR Default

•Non-Metered Lighting (street lights, security lights, etc)

•Non-Metered Flat (traffic signals, communication equipment, etc)

ERCOT WEATHER ZONES

1Flat

Profile

65 Unique Profiles Daily

8 AdjustedStatic Profile

Types

8 Weather

Zones

ERCOT HAS 65 UNIQUE PROFILES

LOAD PROFILING METHODOLOGY

•Adjusted Static Models for metered Load Profiles

•Engineering estimates for non-metered loads

•Scaled profiles based on meter readings spanning the trade day or if unavailable previous meter readings

•Proxy day profiles for IDR premises if trade day data unavailable

•Un-scaled profiles for both IDR and NIDR premises when individual meter data is unavailable

•Supplemental Load Profiling

–Time-Of-Use (chunking)

–Direct Load Control (lagged dynamic)

LOAD AND UFE – ERCOT 2003 PEAK Based on True-up Settlement

This is a graph of load and UFE on the Peak Day in 2003.

ERCOT Load and UFE2003 Peak Day - August 7, 2003

-2000

0

2000

4000

6000

8000

10000

12000

14000

16000

1 9 17 25 33 41 49 57 65 73 81 89

Interval

MW

H

-2

-1

0

1

2

3

4

Perc

ent

ERCOT LOAD

Percent UFE

UFE

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 Positive UFE indicates load/losses are underestimated

UFE (unaccounted for energy) is computed as follows:UFE = Generation – (Load + Losses)

UFE Basics

Net Generation for Settlement Interval

Interval Data Energy Usage

Profiled Energy Usage Non-Interval Data

Non-Metered Accounts

Losses:Transmission &

Distribution

UFEGAP - - - - - - >

Net GenerationCompared toLoad Buildup

DATA VERIFICATION IN THE SETTLEMENT PROCESS

UFE is computed for each 15-minute interval of a settlement run.

Initial

Final

Settlement

True-Up

Initial Settlement(17 days after the trade day)

Final Settlement(59 days after the trade day)

True-up and Resettlement (6 months to up to several years after the trade day.)

The latest resettlement in each interval is used in the analysis for Initial, Final and True-Up.

2003 UFE Mwh by Month

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

Month of 2003

Mw

h

Jan AprMarFeb May Jun Jul Aug Sep Oct Nov Dec

SR01

Annual Total = 1,673,000 MWh

STATISTICAL RESULTS

SR03

MEAN MEDIAN MIN MAX MEAN MEDIAN MIN MAX

2002 34,156 32,319 19,816 55,912 2002 2,321 2,257 0 6,969

2003 32,803 31,280 20,047 59,695 2003 857 759 0 3,906

2002 33,578 31,754 20,370 56,622 2002 1,666 1,579 0 5,654

2003 32,544 31,001 19,856 59,741 2003 711 603 0 3,728

2002 32,512 30,645 19,935 55,520 2002 838 771 0 3,803

2003 32,341 30,773 19,607 59,554 2003 672 528 0 4,065

MEAN MEDIAN MIN MAX MEAN MEDIAN MIN MAX

2002 -2,176 -2,228 -6,969 5,673 2002 -6.4 -6.6 -19.4 20.2

2003 -314 -400 -3,906 3,798 2003 -1.2 -1.3 -11.3 10.4

2002 -1,593 -1,575 -5,954 3,427 2002 -4.9 -4.9 -17.1 10.4

2003 -14 -126 -3,172 3,728 2003 -0.2 -0.4 -9.3 10.4

2002 -461 -556 -3,371 3,803 2002 -1.6 -1.8 -12.9 11.7

2003 191 71 -2,886 4,065 2003 0.5 0.2 -7.3 10.9

INITIAL

LOAD (MW)

INITIAL

UFE as PERCENT of LOAD

UFE as PERCENT of LOAD

UFE (MW)

|UFE| (MW)

TRUE UP

UFE (MW)

|UFE| (MW)LOAD (MW)

|UFE| (MW)

UFE as PERCENT of LOAD

TRUE UP

FINAL

TRUE UP

INITIAL

FINAL

LOAD (MW)

FINAL

TRUE UP

INITIAL

FINAL

UFE (MW)

STATISTICAL RESULTS (CONTINUED)

2002 UFE has a negative bias across all settlements.

2003 UFE has a negative bias for Initial and final Settlement, positive bias for True-up.

2003 UFE for True-up has a mean of 0.5% and a median of 0.2% as compared to -1.6% and -1.8% respectively for 2002.

Mean and Median UFE values are similar indicating the UFE distributions are not skewed.

From Initial to Final thru True-Up settlements, UFE gets closer to 0 indicating more complete usage data improves UFE.

SR04

MEAN MEDIAN MIN MAX

2002 6.8 6.7 0 20.2

2003 2.7 2.3 0 11.3

2002 5.1 4.9 0 17.1

2003 2.2 1.9 0 10.4

2002 2.6 2.4 0 12.9

2003 2.1 1.7 0 10.9

|UFE as PERCENT of Load|

|UFE as PERCENT of Load|

INITIAL

FINAL

|UFE as PERCENT of Load|

TRUE UP

Generation Differences Between Initial and Final Settlements

8.4% of the intervals had Initial to Final differences greater than 100 MW

Differences greater than 300 MW occurred for 1.0 % of the intervalsGDF01

Generation Differences Between Final and True-Up Settlements

GDF02

5.5% of the intervals had Final to True-Up differences greater than 100 MW

Differences greater than 300 MW occurred for 0.1 % of the intervals

GDF04

Change in Generation between Settlements

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

-0.05 0.05 0.15 0.25 0.35 0.45 0.75 1.25

Percent Change in Gen Mwh

Perc

en

t o

f In

terv

als

Initial to Final

Final to True-Up

2003 Distribution of UFEas Percent of ERCOT Load

The UFE percent moves in a positive direction from Initial to Final thru True-Up.UFD03

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

-10.0 -9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.1

UFE Percent of ERCOT Load - 2003

Dis

trib

uti

on

of

UF

E P

erc

en

t o

f E

RC

OT

Lo

ad

Initial Final True-Up

Initial Settlement with95% Confidence Interval

CIP01

UFE Percent of ERCOT LoadWeekly for 2003

-10

-8

-6

-4

-2

0

2

4

6

8

10

Day of the Week

UF

E P

erc

en

t o

f E

RC

OT

Lo

ad

Median

5th Percentile

95th Percentile

Sun TueMon Wed Thur Fri Sat

Final Settlement with95% Confidence Interval

CIP02

UFE Percent of ERCOT LoadWeekly for 2003

-10

-8

-6

-4

-2

0

2

4

6

8

10

Day of the Week

UF

E P

erc

en

t o

f E

RC

OT

Lo

ad

Median

5th Percentile

95th Percentile

Sun TueMon Wed Thur Fri Sat

True-Up Settlement with95% Confidence Interval

CIP03

UFE Percent of ERCOT LoadWeekly for 2003

-10

-8

-6

-4

-2

0

2

4

6

8

10

Day of the Week

UF

E P

erc

en

t o

f E

RC

OT

Lo

ad

Median

5th Percentile

95th Percentile

Sun TueMon Wed Thur Fri Sat

CIP04

Median ComparisonBy Settlement Type

UFE Percent of ERCOT Load

-4

-3

-2

-1

0

1

2

3

4

Day of the Week

UF

E P

erc

en

t o

f E

RC

OT

Lo

ad

Initial

Final

TrueUp

Sun Mon Tue Wed Thu Fri Sat

UFE by Weekday General Observations

The UFE Percent of ERCOT Load graphs indicate UFE as a percent of load varies over a wide range between the Median, the 5th Percentile and 95th Percentile.

The difference between the Median, the 5th Percentile and 95th Percentile decreases from Initial to Final through True-Up settlements.

For all settlements there is a well-defined cyclical component across all days of the week. UFE is negative during the off-peak hours and positive during on-peak hours.

Median values move in a positive direction from Initial to Final through True-Up settlements across all days of the week indicating settlements based on more complete usage data result in a reduction in the over-estimation of load.

CIP05

UFE Percent of ERCOT Load and ERCOT Load - Spring 2003

SEA01

-8

-6

-4

-2

0

2

4

6

Day of the Week

UF

E P

erc

en

t o

f E

RC

OT

Lo

ad

0

5000

10000

15000

20000

25000

30000

35000

ER

CO

T L

oa

d (

MW

)

Initial Final True-Up Total ERCOT Aggregated Load Adjusted for Losses

Sun Mon Tue Wed Thu Fri Sat

UFE Percent of ERCOT Load and ERCOT Load - Summer 2003

SEA02

-8

-6

-4

-2

0

2

4

6

Day of the Week

UF

E P

erc

en

t o

f E

RC

OT

Lo

ad

15000

20000

25000

30000

35000

40000

45000

50000

ER

CO

T L

oa

d (

MW

)

Initial Final True-Up Total ERCOT Aggregated Load Adjusted for Losses

Sun Mon Tue Wed Thu Fri Sat

UFE Percent of ERCOT Load and ERCOT Load - Fall 2003

SEA03

-8

-6

-4

-2

0

2

4

6

Day of the Week

UF

E P

erc

en

t o

f E

RC

OT

Lo

ad

20000

25000

30000

35000

40000

45000

50000

55000

ER

CO

T L

oa

d (

MW

)

Initial Final True-Up Total ERCOT Aggregated Load Adjusted for Losses

Sun Mon Tue Wed Thu Fri Sat

UFE Percent of ERCOT Load and ERCOT Load - Winter 2003

SEA04

-8

-6

-4

-2

0

2

4

6

Day of the Week

UF

E P

erc

en

t o

f E

RC

OT

Lo

ad

20000

25000

30000

35000

40000

45000

50000

55000

ER

CO

T L

oa

d (

MW

)

Initial Final True-Up Total ERCOT Aggregated Load Adjusted for Losses

Sun Mon Tue Wed Thu Fri Sat

SEA05

Seasonal Comparison of Medians Initial Settlement

-8

-6

-4

-2

0

2

4

6

Day of the Week

UF

E P

erce

nt

of

Lo

ad

Spring Summer Fall Winter

Sun Mon Tue Wed Thu Fri Sat

SEA06

Seasonal Comparison of MediansFinal Settlement

-8

-6

-4

-2

0

2

4

6

Day of the Week

UF

E P

erce

nt

of

Lo

ad

Spring Summer Fall Winter

Sun Mon Tue Wed Thu Fri Sat

SEA07

Seasonal Comparison of Medians True-Up Settlement

-8

-6

-4

-2

0

2

4

6

Day of the Week

UF

E P

erce

nt

of

Lo

ad

Spring Summer Fall Winter

Sun Mon Tue Wed Thu Fri Sat

Percent UFE vs ERCOT LoadInitial Settlement

MPL01

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

21000 26000 31000 36000 41000 46000 51000 56000

ERCOT Load (MW)

Pe

rce

nt

UF

E

Median

5th Percentile

95th Percentile

Regression on Total Aggregated Load

Percent UFE vs ERCOT LoadFinal Settlement

MPL02

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

20000 25000 30000 35000 40000 45000 50000 55000

ERCOT Load (MW)

Pe

rce

nt

UF

E

Median

5th Percentile

95th Percentile

Regression on Total Aggregated Load

Percent UFE vs ERCOT LoadTrue-Up Settlement

MPL03

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

20000 25000 30000 35000 40000 45000 50000 55000

ERCOT Load (MW)

Perc

en

t U

FE

Median

5th Percentile

95th Percentile

Regression on Total Aggregated Load

Comparison of Median Percent UFEBy Settlement Type

MPL04

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

20000 25000 30000 35000 40000 45000 50000 55000

ERCOT Load (MW)

Pe

rcen

t U

FE

Initial

Final

True Up

General ObservationsPercent UFE vs ERCOT Load

UFE = Generation – (Load + Losses)

There is a statistically significant relationship between load and UFE.

There is wide variability between the median, 5th and 95th percentiles of percent UFE for initial and final settlements. Variability decreases dramatically for the true up settlements.

As load increases, median UFE for all settlements moves in a positive direction indicating (Load + Losses) are over estimated at low load intervals and are progressively more under estimated as load increases.

MPL05

General ObservationsPercent UFE vs ERCOT Load

UFE shifts in a positive direction from initial to final thru true-Up settlements indicating settlements based on more complete usage data result in a reduction in the over-estimation of load.

UFE is closest to zero between 30,000 to 40,000 MW. UFE for Initial settlement becomes worse than UFE for Final settlement at approximately 38,000 MW of ERCOT load. Similarly, UFE for Final settlement becomes worse than UFE for True-Up at approximately 34,000 MW of ERCOT load.

There is a well-defined cyclical component across all days of the week however the UFE cycles are out of phase with the load cycles

MPL05

Transmission Plus Distribution Loss versus Total Load

MPL07

3.0

3.5

4.0

4.5

5.0

5.5

6.0

20000 25000 30000 35000 40000 45000 50000 55000

ERCOT Load (MW)

Per

cen

t L

oss

es

Median

5th Percentile

95th Percentile

Note: Percent losses includes distribution plus transmission losses.

MPL08

Distribution Loss versus Distribution Load

2.0

2.5

3.0

3.5

4.0

4.5

5.0

16000 20000 24000 28000 32000 36000 40000 44000

Total ERCOT Load - NOIE Load - Trans Losses (MW)

Perc

en

t D

istr

ibu

tio

n L

os

se

s

Median

5th Percentile

95th Percentile

MPL09

Transmission Loss versus Total Actual Load

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

20000 25000 30000 35000 40000 45000 50000 55000 60000

Total ERCOT Actual Load

Pe

rcen

t T

ran

sm

issio

n L

osse

s

Spring Median

Summer Median

Fall Median

Winter Median

Annual Median

UFE costs are calculated by multiplying the UFE (MWH) times the Market Clearing Price for Load (MCPEL)($/MWH) for each 15-minute interval in 2003.

MCPEL is a function of Congestion Zone. MCPEL is the same across all Congestion Zones if there is no congestion.

The CM Zones for 2003 are: Houston, North, South and West

UFE Cost Analysis by Congestion Management Zone

UCT01

UFE cost values per interval are calculated for:

positive and negative UFE

the absolute value of UFE

the net value of UFE.

Median UFE cost analyses include:

Seasonal as defined in the Profile Assignment Decision Tree

Spring: March 1 – April 30

Summer: May 1 – September 30

Fall: October 1 – November 30

Winter: December 1 – February 28

Monthly

Hour of the week.

UFE Cost Analysis by Congestion Management Zone

UCT01

UFE Cost by Month across all CMZones

UFE Cost by Month Across All CMZones

-20,000,000

-10,000,000

0

10,000,000

20,000,000

30,000,000

40,000,000

50,000,000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month of 2003

Do

llars

Positive UFE

Negative UFE

Net UFE

UCT03

Absolute ValueUFE Cost by Month and CMZone

UCT04

0

10,000,000

20,000,000

30,000,000

40,000,000

50,000,000

60,000,000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month of 2003

Do

lla

rs

West 03

South 03

North 03

Houston 03

CMZone:

Net UFE Cost by Month and CMZone

UCT05

0

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

30,000,000

35,000,000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month of 2003

Do

lla

rs

West 03

South 03

North 03

Houston 03

CMZone:

SUM of UFE Dollars – SpringAbsolute Value and Net UFE

UCT17

Spring: March 1 - April 30

-400,000

-200,000

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

Day of the Week

Do

lla

rs

SUM[ABS(UFE)] SUM[Net(UFE)]

Sun Mon Tue Wed Thu Fri Sat

MCPE = 167.32 $/MW

UCT18

SUM of UFE Dollars – SummerAbsolute Value and Net UFE

Summer: May 1 - Sept 30

-400,000

-200,000

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

Day of the Week

Do

lla

rs

SUM[ABS(UFE)] SUM[Net(UFE)]

Sun Mon Tue Wed Thu Fri Sat

UCT19

SUM of UFE Dollars – FallAbsolute Value and Net UFE

Fall: Oct 1 - Nov 30

-400,000

-200,000

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

Day of the Week

Do

lla

rs

SUM[ABS(UFE)] SUM[Net(UFE)]

Sun Mon Tue Wed Thu Fri Sat

MCPE = $428.27

UCT20

SUM of UFE Dollars – WinterAbsolute Value and Net UFE

Winter: Dec 1 - Feb 28

-400,000

-200,000

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

Day of the Week

Do

llars

SUM[ABS(UFE)] SUM[Net(UFE)]

Sun Mon Tue Wed Thu Fri Sat

MCPE = 990 $/MW

RESULTS and CONCLUSIONSThe total dollars for the absolute value of UFE in 2003 amounted to $307 million. The net UFE amounted to $157 million.

During 2003, there was a strong daily cyclical component to median UFE (related to load).

Median UFE tends to be negative during the off-peak intervals and positive during on-peak intervals. This pattern is similar for all days of the week.

Median UFE tends to be negative during low load intervals and moves in a positive direction as load increases.

Median UFE values move in a positive direction from initial to final thru true-up indicating settlements based on more complete usage data result in a reduction in the over-estimation of load.

There is less variance in UFE for true-up settlements when compared to initial and final settlements.

The pattern of median UFE is significantly different across seasons.

Continue with Load Research Project (PUCT Project 25516)

Improve Profile ID assignment processContinue to improve usage data loading accuracy and timelinessIncrease the number of IDR’s

Evaluate Lagged Dynamic sampling techniques and their application to the ERCOT System

Continue to evaluate improvements to algorithms for missing IDR and NIDR data estimation

Continue to make improvements to loss estimations

Explore alternative methods for UFE allocation

UFE Zones

By Substation Assignment

By Weather Zone

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