Texas is the U.S. state that produces the most renewable energy in terms of sheer quantity. And one that also experiences some of the most extreme weather out of all the U.S. regions. This conversation will provide a unique perspective as to how ERCOT balances a regional energy system that counts on some of the highest renewable penetration rates with reliability and resilience in a very congested transmission network throughout its most challenging season, reflecting on Summer 2018 data.

1. Power & Renewables Summit 2018
Keynote Presentation
Cheryl Mele
Senior Vice President & Chief Operating Officer
November 14, 2018

2. PUBLIC 2
The interconnected
electrical system serving
most of Texas, with
limited external
connections
• 90% of Texas electric
load; 75% of Texas land
• 73,473 MW peak,
July 19, 2018
• More than 46,500 miles
of transmission lines
• 600+ generation units
ERCOT connections to other grids
are limited to ~1,250 MW of direct
current (DC) ties, which allow
control over flow of electricity
600 MW with SPP
30 MW with CENACE
at Eagle Pass
100 MW with CENACE
at Laredo 300 MW with CENACE at McAllen
220 MW with SPP
The ERCOT Region
Texas RE

3. PUBLIC
Installed Generating Capacity in ERCOT
3
2016
Generating
Capacity
Capacity available:
91,195 MW
2017
Generating
Capacity
Capacity available:
93,546 MW
• Summer generation capacity
information provided by December CDR
Reports for 2015, 2016 and 2017.
• Reflects operational installed capacity ―
excludes units designated as indefinitely
mothballed or under extended outage,
and accounts for rating changes
reported by resource owners.
• Other category includes hydro,
biomass-fired units and DC ties.
2018
Generating
Capacity
Capacity available:
94,626 MW
Natural
Gas
53%
Coal
21%
Nuclear
5%
Wind
20%
Other
2%
Natural
Gas
54%
Coal
22%
Nuclear
5%
Wind
18%
Other
1%
Natural
Gas
55%
Coal
17%
Nuclear
5%
Wind
21%
Other
2%

4. PUBLIC 4
2018 Actual Peak
Demand (7/19/18)
Final 2018 Summer
SARA*
Total Resources, MW 77,558 78,184
Thermal and Hydro 65,200 66,457
Private Use Networks, Net to Grid 3,019 3,298
Switchable Generation Resources 3,057 2,727
Wind Capacity Contribution 4,229 4,193
Solar Capacity Contribution 1,136 1,120
Non-Synchronous Ties 917 389
Peak Demand, MW 73,308 72,756
Reserve Capacity, MW 4,250 5,428
Total Outages, MW 2,075* 4,349
Extreme Outage Scenario 6,915
Capacity Available for Operating Reserves, MW 2,175 1,079
The Summer 2018 Seasonal Assessment of Resource
Adequacy (SARA) values vs. actuals at peak demand
No outages greater than
500 MW
Source: Final 2018 Summer SARA
* The totals for the Final 2018 Summer SARA column combine multiple
rows into a single row in some cases (E.g., already in-service Thermal and
Hydro Resources with planned Thermal and Hydro Resources).
** The outage information in this table was extracted on September 4, 2018.

5. PUBLIC
A closer look at the peak demand day of July 19
5
*Off-line capacity is a summation of capacity from resources that were simply off-line
and those providing non-spinning reserves as an off-line resource.
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
G,H,andI(MW)
A,B,C,D,EandF(MW)
Hour Ending
Hourly Average Demand, Capacity, and Reserves on 7/19/2018
A: Outages B: Quick-Start Resources C: Off-Line
D: Renewable HSL E: Non-renewable HSL F: Load
G: PRC H: Wind I: Solar
PRC = 2300

6. PUBLIC
Higher amount of Intermittent Renewable Resource (IRR) MW
occurred during the 2018 peak (7/19/18), relative to 2017 peak
(7/28/17)
6
0
1,500
3,000
4,500
6,000
7,500
9,000
10,500
12,000
13,500
15,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
MW
Hour Ending
7/19/18 Wind 7/19/18 Solar
7/28/17 Wind 7/28/17 Solar
ERCOT IRR Generation
In the Final 2018 Summer SARA, wind contribution was 4,193 MW vs 4,229 MW actual and solar contribution was 1,120 MW vs 1,136 MW actual.
ERCOT “Peak” Hours
• Average wind generation during peak hours on July 19, 2018 was ~800 MW higher than on July 28,
2017. Average solar generation during peak hours on July 19, 2018 was ~400 MW higher than on
July 28, 2017.
• Average wind generation during peak hours on July 19, 2018 was ~1,900 MW lower than the average
for summer 2018 during those same hours of the day.