Wind Integration in ERCOT 

Beth Garza

Director, ERCOT IMM

bgarza@potomaceconomics.com

512-225-7077

EIA Conference

June 4, 2018
Thoughts on ERCOT’s Wind Generation Experience

• More wind, more wind, more wind

• Better reliability metrics

• Reduced ancillary services requirements

2
Geography

3

H

Mexico

D

SA
ERCOT Annual Energy by Fuel Type

4

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Annual Generation Mix

Other

Natural Gas

Wind

Coal

Nuclear
Wind Output and Estimated Curtailment

5

8.4%

17.1%

7.7%

8.5% 3.8%

1.1%

0.5%

1.0%

1.6%

2.5%

0

10

20

30

40

50

60

70

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Wind Production & Curtailment (TWh)

Estimated Curtailment

Output
More wind producing more

6

0%

5%

10%

15%

20%

25%

30%

35%

40%

0

5

10

15

20

25

2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Annual Capacity Factor

Installed Wind Generation 

(GW)

Installed Wind Capacity

Annual capacity factor
2017 Unit Specific Wind Generation Capacity Factor

7

0%

10%

20%

30%

40%

50%

60%

Capacity Factor

InService Year

Coastal Panhandle All Other Wind
Improved Reliability Metrics

8
Declining Requirements for Ancillary Services

9

0

1

2

3

4

5

6

2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Reserve Quantities - GW

RegDown NonSpin Responsive RegUp
Key Enablers

• Common carrier model for Transmission

• Centralized forecasting of wind output

– for every wind generator

– ramp events

• Real-time output variations accommodated

10
ERCOT Transmission

• All loads pay for all transmission 

• Generators are not required to make any transmission 

investment past their step-up transformer

• Public policy choice to build out transmission system in 

advance of need

– CREZ investment - $7B

11
$0

$10

$20

$30

$40

$50

$60

2000200120022003200420052006200720082009201020112012201320142015201620172018

Rate ($ per kW - year)

Transmission Costs

12

$0.0

$0.5

$1.0

$1.5

$2.0

$2.5

$3.0

$3.5

$4.0

0

10

20

30

40

50

60

70

80

2000200120022003200420052006200720082009201020112012201320142015201620172018

Average 4CP Load (GW)

Annual TCOS ($Billion)

Indicative – Not Actual
Transmission and Energy costs

13

0

1

2

3

4

5

6

7

8

9

0

10

20

30

40

50

60

70

80

90

2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

$ per MWh

$ per MBtu

RT Load weighted Avg price Average transmission cost Gas

Indicative Transmission Costs

Not Actual
ERCOT Wind Forecasts

• Hourly forecast of wind production potential for each Windpowered Generation Resource (WGR) updated hourly, for 

next 168 hours. (STWPF)

• Determine probability distribution of the hourly production 

potential from all wind-power in ERCOT for each of the next 

168 hours. (TEWPF)

• WGR provide turbine availability via outage scheduler

14
ERCOT Wind Forecasts - WGR requirements

• Install and telemeter to ERCOT site-specific 

meteorological information necessary to 

produce the STWPF and TEWPF forecasts. 

• ERCOT requires the following data be 

provided from each WGR every five minutes:

15

MW Average

Wind Speed

Wind Direction

Temperature

Barometric Pressure

HSL Average

Num of Turbines On

Num of Turbines Off

Num of Turbines Unknown

Curtailment Flag
Accommodating variable output

• ERCOT dispatch executes every 5 minutes

• WGR High Sustained Limit (HSL), when not curtailed, to be 

telemetered as equal to the WGR’s current meter reading

• When curtailed, WGR’s receive a curtailment flag from 

ERCOT along with their Base Point (dispatch level)

• When WGR is curtailed, the HSL to be telemetered is the 

expected output, but for the curtailment

• WGR ramping when curtailed limited to 20% per minute, 

unless installed before 2009 and have a good excuse

16
Negative prices

17

0

100

200

300

400

500

600

700

800

900

1000

2011 2012 2013 2014 2015 2016 2017

Hours

WEST Only ERCOT Wide Other
In Summary

• ERCOT’s experience

– More wind, more wind, more wind

– Better reliability metrics

– Reduced ancillary services requirements

• Enablers

– Common carrier model for Transmission

– Centralized forecasting of wind output

– Real-time output variations accommodated

18