ERCOT 4 Settlement Load Zones
NORTH
North Texas / Dallas-Fort Worth
Dallas-Fort Worth Metroplex and North Texas — ERCOT's largest demand zone. Data center epicenter with hyperscalers (Microsoft, Google, Meta, Amazon) projected to add 10+ GW of new load by 2030. Highest LMP in ERCOT during summer peaks. Net importer from WEST via CREZ corridors. Key substations: Eagle Mountain, Lewisville, Denton 345kV. Primary generation: gas peakers, small wind. Fastest-growing load zone in ERCOT — major driver of new transmission need.
HOUSTON
Houston / Gulf Coast
Harris County and Gulf Coast — ERCOT's petrochemical and industrial load hub. LNG export facilities (Freeport, Sabine Pass nearby) create correlated load patterns with gas markets. Key substations: Quail Run 345kV, Tom Light 345kV. STP Nuclear (2,708 MW) in Matagorda County is the zone's primary baseload. Net importer during summer peaks. Hurricane exposure is primary reliability risk — Beryl (2024) disrupted 2.7 million customers. Highest average LMP in ERCOT.
SOUTH
South Texas / San Antonio / Rio Grande Valley
San Antonio, Corpus Christi, Laredo, and the Lower Rio Grande Valley. Key utilities: CPS Energy (San Antonio, ~3,000 MW load), AEP Texas Central (Corpus Christi). Wind + solar growing rapidly in south Texas — multiple offshore wind proposals near Corpus Christi. Mexico DC interconnects at Laredo (156 MW) and Eagle Pass (36 MW) provide emergency exchange with CFE. Second-lowest LMP in ERCOT. New solar projects (Cameron, Starr, Hidalgo counties) rapidly adding capacity.
WEST
West Texas / Midland-Odessa / Lubbock / El Paso
Midland-Odessa, Lubbock, El Paso area — ERCOT's smallest load but largest generation zone. Wind + solar dominated. Exports power to NORTH and HOUSTON via CREZ corridors. Lowest LMP in ERCOT — averaging $22/MWh in 2023 due to persistent congestion and wind surplus. Negative LMPs occur 15–20% of annual hours. Developers face serious basis risk here. Permian Basin oil industry creates some industrial load growth but insufficient to balance generation surplus. Urgent need for new transmission per LTSA.
ERCOT 8 Weather Zones
| Weather Zone | Key Counties | Dominant Resource | Peak Temp | Grid Risk |
|---|
| FAR WEST | Reeves, Pecos, Brewster | Wind + Solar | 110°F | Transmission Export Limit |
| WEST | Midland, Ector, Howard | Wind + Solar | 108°F | Congestion on CREZ Lines |
| NORTH CENTRAL | Dallas, Tarrant, Denton | Gas + Solar | 107°F | Load Pocket — Import Dependent |
| SOUTH CENTRAL | Travis, Hays, Williamson | Gas + Solar | 108°F | Austin Data Center Growth |
| COAST | Harris, Galveston, Brazoria | Gas + Industrial | 97°F | Hurricane Exposure |
| EAST | Tyler, Nacogdoches, Smith | Gas | 100°F | Limited Renewables / Stable |
| NORTH | Wichita, Archer, Clay | Wind + Gas | 110°F | Panhandle Export Corridor |
| SOUTH | Nueces, Hidalgo, Cameron | Wind + Gas | 106°F | Mexico DC Interconnect |
ERCOT Interconnections with Other Grids
Eastern Interconnection
DC Ties — Lamar & Dunlap
Two DC (direct current) ties connect ERCOT to the Eastern Interconnection: Lamar (210 MW) and Dunlap (220 MW). Very limited capacity — combined 430 MW vs. 90 GW ERCOT peak demand. Cannot use AC power flows for emergency transfers. Operated by Oncor and AEP Texas.
ERCOT Synchronous Interconnection Policy
Mexico
CFE DC Ties — Eagle Pass & Laredo
Two DC ties to CFE (Comisión Federal de Electricidad) grid in Mexico: Eagle Pass (36 MW) and Laredo (156 MW). Occasionally import power from Tamaulipas state. Emergency support only — total capacity 192 MW. Cross-border power trade is minimal relative to ERCOT's size.
NERC Interconnection Map 2024
Grid Vulnerability
ERCOT's Deliberate Isolation
ERCOT's total external interconnection capacity (~600 MW) is tiny relative to ~90 GW peak demand. This isolation preserves Texas's intrastate exemption from FERC jurisdiction but creates reliability risk. It was a primary reason Winter Storm Uri caused such extreme conditions — no ability to import meaningful emergency power from adjacent grids.
NERC Event Analysis — Winter Storm Uri 2021
Proposed
New Mexico HVDC Tie
Bills introduced in Texas legislature to add HVDC tie (~1,000 MW) from New Mexico (Western Interconnection). Would enable capacity imports during extreme events while preserving Texas's regulatory independence. No PUCT approval as of mid-2024. Debate continues over FERC jurisdiction implications.
Texas HB 2781 — 88th Legislature