South Texas Project
STP Nuclear Operating Company · Matagorda County · ERCOT
South Texas Project is a two-unit pressurized-water nuclear station in Matagorda County, Texas. EIA reports 2,580 MW of net summer capability for Plant 6251. STP Nuclear Operating Company operates the site; current ownership is Constellation Energy (44%), CPS Energy (40%), and Austin Energy (16%). The units settle at ERCOT resource nodes STP_STP_G1 and STP_STP_G2 and connect through the site’s 345 kV switchyard.
Overview
Key fields
- Reported capacity
- 2,580 MW
EIA-reported net summer capability; other nameplate and seasonal ratings may differ.
- Technology
- Nuclear
Primary generation technology.
- Registry anchor
- Plant 6251
STP Nuclear Operating Co · Matagorda County · ERCOT
- Operating status
- Operating
South Texas Project is operating.
- Market nodes
- STP_STP_G1 · STP_STP_G2
ERCOT resource-node settlement points
- Resource stack
- 6 resources
STP_STP_G1_J01 · STP_STP_G1_J03 · STP_STP_G1_J04
Profile
- Market nodes
- STP_STP_G1 · STP_STP_G2.
- Ownership
- Constellation Energy 44% · CPS Energy 40% · Austin Energy 16%. CPS has agreed to acquire another 2% from Constellation, but CPS’s FY2026 audited statements say the transaction remains pending.
- Physical build
- Two Westinghouse four-loop pressurized-water reactor units, each licensed by the NRC at 3,853 MWt, connected through the site’s 345 kV switchyard.
Structured profile
- Operating status
- operating
South Texas Project is operating.
- Location
- Matagorda County
ERCOT
- Operator
- STP Nuclear Operating Co
- Asset role
- nuclear
ERCOT · Matagorda County
- Owner
- Constellation 44% · CPS 40% · Austin 16%
Current ownership. CPS’s agreement to acquire another 2% remains pending in its FY2026 audited statements.
Units and generators
Operating generator records and technology attributes reported through EIA-860.
| Generator | Capacity | Technology | Operation | Status |
|---|---|---|---|---|
| 1 | 1,354.3 MW 1,300 MW summer | Nuclear Nuclear · ST | Aug 1988 | Operating |
| 2 | 1,354.3 MW 1,280 MW summer | Nuclear Nuclear · ST | Jun 1989 | Operating |
Performance
Monthly EIA generation history and recent market-resource behavior where linked telemetry is available.
Peer context
- Technology capacity
- 2,708.6 MW
- National rank
- #5
- TX rank
- #1
Monthly generation
Download CSVMonthly generation is reported through EIA-923. Capacity factor uses the current EIA nameplate capacity and is shown only for complete calendar years.
ERCOT disclosed dispatch
6 ERCOT market resources · Nuclear
Generation
3 mo through May 22, 2026Capacity factor is average output vs. this plant's observed peak.
Output by hourlocal time · 90 days through May 22, 2026
Latest disclosed outputhourly · 2 weeks ending May 22, 2026
Generation from ERCOT's 60-Day SCED Disclosure (≈60-day lag), summed over this site's market resources.
Grid and market context
Deterministic links to ERCOT market resources, price records, outage disclosures, queue records, and nearby infrastructure. Candidate joins remain labeled until corroborated.
Market registration
ERCOT public disclosuresOperating context
ERCOT market recordsNearby substations
HIFLD infrastructure inventoryCommercial, land, and environmental record
Source-backed project transactions, agreements, land records, permits, and environmental disclosures. Portfolio and adjacent-project facts remain explicitly scoped.
Land and environmental record
Related parties and identifiers
Parties, market resources, and identifiers tied to this asset, with owner, operator, developer, EPC, compliance provider, and interconnecting entity roles kept separate.
Relationship graph
Drag organizations to explore the network. Select a node to pin its details and available page link.
Parties and identifiers
| Relationship | Entity | Basis |
|---|---|---|
| Operator | Operator for South Texas Project | |
| Market resources | STP_STP_G1_J01, STP_STP_G1_J03, STP_STP_G1_J04, STP_STP_G2_J01, STP_STP_G2_J03 | 6 linked ERCOT resources. |
| Grid selection | plant:plant-6251 | Canonical asset page /ercot/assets/plant/south-texas-project. |
Reporting portfolio
Portfolio membership follows the latest EIA-860 reporting entity. It does not imply ultimate ownership.
Timeline and sources
Project milestones and public references behind the asset profile.
Project timeline
- Operating license issued (Unit 1)Source
NRC operating license issued for STP (operator listed as STP Nuclear Operating Co.).
- Generator enters operationEIA-860
EIA-860 lists generator 1 with this operating date.
- Generator enters operationEIA-860
EIA-860 lists generator 2 with this operating date.
- Transaction completed — NRG sale to ConstellationNRG Complet...
NRG announced completion of the sale of its 44% interest in the South Texas Project to Constellation for $1.75 billion on November 1, 2023.
- Latest disclosed generation interval
ERCOT SCED disclosure is delayed, so plant performance windows end at the latest disclosed interval.
Sources
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