South Texas 1
Online · 100% powerSTP Nuclear Operating·Palacios, TX·PWR·1,300 MWe
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Composite Operational Excellence Score (0-100) — average percentile rank across 7 dimensions in three sub-scores: Reliability (capacity factor, forced outage days, B2B avg streak), Efficiency (fuel utilization, refuel duration), and Discipline (startup duration, scram count). 5-year window. Higher = more operationally excellent. Click to see the full breakdown.
Excellence
Rank locked · 93 units
Subscribers
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Current reactor power level from the most recent NRC daily report.
100%
Power
ONLINE
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Days of continuous operation since the last outage ended. Ranked against all operating units.
183
Current Run
days
#42 of 95
Mid Quartile
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Longest recorded period of continuous operation between outages.
580
Record Run
days
#51 of 95
Mid Quartile
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (454 days for this 18-month cycle unit) with no trips to 0% power.
9
B2B Runs
#19 of 86
Top Quartile
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Lifetime capacity factor: average power level across all recorded days (100% = always at full power). Ranked against all NRC-tracked units.
89.8%
Capacity Factor
#51 of 95
Mid Quartile
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Net electricity actually generated over the most recent 12 months reported by the U.S. Energy Information Administration (Form EIA-923), summed across every unit at this plant. These are authoritative actuals, not an estimate.
20.23 TWh
Net Generation
EIA-923 · 12 mo to 2026-07 · plant total
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Total NRC-reported scram events (emergency reactor shutdowns). Ranked fleet-wide — fewer scrams = better rank.
5
Scrams
#24 of 94
Top Quartile
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Years since commercial operation began. License remaining: 20.8 years.
38.2
Operating Age
years
20.8 yrs remaining
Excellence Score, Records & Plant Facts
B2B CHAMPION
813 days without a trip
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9 Career Runs · 1 since last trip
Champion since Feb 6, 2026
Breaker-to-Breaker Runs 9 runs
Breaker-to-breaker runs measure continuous operation between refueling outages using a cycle-adjusted threshold (90% of cycle length minus RFO duration). An active streak means the unit has been running continuously since the last refueling with no trips to 0% power.
South Texas 1 has logged 9 breaker-to-breaker runs, continuous stretches from one refueling to the next with no trip to zero power. Its longest ran 534 days, and its runs average 513 days.
534
Best Run (days)
1RE12 (2005-04-15) → 1RE13 (2006-10-01)
513
Avg Run (days)
★ Triple breaker-to-breaker
1RE12 → 1RE13 → 1RE14 → 1RE15
All Runs
| 2024-11-09 | 2026-03-21 | 497 days | 1RE25 → 1RE26 |
| 2021-11-07 | 2023-03-18 | 496 days | 1RE23 → 1RE24 |
| 2018-11-10 | 2020-03-14 | 490 days | 1RE21 → 1RE22 |
| 2017-04-27 | 2018-10-06 | 527 days | 1RE20 → 1RE21 |
| 2014-06-01 | 2015-10-18 | 504 days | 1RE18 → 1RE19 |
| 2011-05-07 | 2012-10-21 | 533 days | 1RE16 → 1RE17 |
| 2008-04-26 | 2009-10-01 | 523 days | 1RE14 → 1RE15 |
| 2006-11-04 | 2008-03-30 | 512 days | 1RE13 → 1RE14 |
| 2005-04-15 | 2006-10-01 | 534 days | 1RE12 → 1RE13 |
About This Site
Written by NukeWorker from public records: facts that do not change. Operator, status and capacity come from the live data elsewhere on this page. Sources: Wikipedia: South Texas Nuclear Generating Station.
South Texas Project Electric Generating Station is in Matagorda County, Texas, near Bay City and about 90 miles southwest of Houston, on a 12,200-acre site west of the Colorado River. A 7,000-acre reservoir filled from the river serves as its cooling source.
Read more
Houston Lighting & Power led the project with Central Power and Light, the City of Austin and the City of San Antonio, and Brown & Root was the original architect and construction firm. Construction began on December 22, 1975. The plant has two Westinghouse four-loop pressurized water reactors, with commercial operation on August 25, 1988, for Unit 1 and June 19, 1989, for Unit 2. Both units were taken offline in February 1993 over problems with auxiliary feedwater pumps, and returned in March 1994 and May 1994.
Facility Statistics
Key performance and lifecycle metrics calculated from NRC operational data. Includes operating age, construction timeline, capacity factor, efficiency, generation totals, and reliability records.
South Texas 1 has operated for about 38.2 years and averaged a 89.8% lifetime capacity factor, generating roughly 282.2 TWh of electricity. Its longest unbroken run reached 580 days.
Lifecycle & Tenure
Operating Age: 38.2 Yrs
Build Time: 12.7 Yrs
Lic. Remaining: 20.8 Yrs
Production & Power
Lifetime CF: 89.8%
Efficiency: 33.7%
Generated: 282.2 TWh
Reliability & Outages
Record Run: 580 Days
Refuelings: 18
Avg Startup: 5.3 Days
Ownership & Construction
The utility or company that owns and operates the facility, the architect-engineer responsible for plant design, and the primary construction contractor. Click names to view all facilities by that entity on the map.
Ownership, operation and management history
| Date | Change | From | To |
|---|---|---|---|
| Feb 2, 2006 | Ownership stake | Texas Genco (44% share) | NRG Energy (44% share) |
| Nov 2023 | Ownership stake | NRG Energy (44% share) | Constellation Energy (44% share) |
CEG
Constellation Energy Corporation
NasdaqGS
$270.74
▲ +11.90 (+4.60%)
Previous Close
258.84
Day's Range
263.12 – 273.21
52-Week Range
228.63 – 406.04
Volume
2,785,585
Delayed quote as of Oct 21, 2026 4:00 PM ET.
Source: Yahoo Finance.
Full quote on Yahoo Finance
South Texas Project is co-owned by Constellation (44%), CPS Energy (40%) and Austin Energy (16%), and operated by STP Nuclear Operating Company. Constellation is the only publicly traded co-owner; it bought the stake from NRG Energy in 2023.
Operational Excellence Score Subscribers
South Texas 1 is rated 0 to 100 on how well it actually runs, scored against every other operating reactor in the US fleet from its own operating record. Subscribers see the score, the three sub-scores behind it, and each of the seven measured inputs.
- This unit's composite score and fleet rank
- Reliability, Efficiency and Discipline sub-scores
- All seven measured inputs, with fleet percentiles
- Rank against comparable units, not just the fleet
- Three-year, five-year and lifetime windows
- Five-year trend, and every other operating US reactor
Included with every outage subscription and with NukeWorker Gold membership. Trading the outage rather than working it? The same record, cut by power market, is on NukeGryd.
Scram History 5 events since 2011
Automatic and manual reactor scram (emergency shutdown) events reported to the NRC since 2011. Includes event dates, trip type, and average recovery time. Click the title to view the full fleet scram dashboard.
South Texas 1 has recorded 5 reactor scrams, or emergency shutdowns, since 2011 (3 automatic, 2 manual). On average the unit was back to full power about 6.4 days after each trip.
Technical Specs
Reactor design specifications including type (PWR/BWR), containment design, nuclear steam supply system manufacturer, thermal and electrical power ratings, and current operational status.
Reactor Type:
PWR
Containment:
PWR-DRYAMB
NSS Supplier:
WEST 4LP
Turbine Supplier:
WESTINGHOUSE ELECTRIC CORPORATION IAEA
Thermal Power:
3853 MWt
Net Capacity:
1300 MWe
Gross Capacity:
1,354 MWe IAEA
Design Capacity:
1,250 MWe IAEA
Efficiency:
33.7%
Status:
Operating
Lifetime Output:
357.5 TWh through 2025 IAEA
Licensing
NRC licensing history including docket number, license type and number, construction permit date, operating license issuance, commercial operation date, license renewal, and expiration date.
Docket #:
05000498
License #:
NPF-76
License Type:
OL-FP
Const. Permit:
1975-12-22
Construction Start:
1975-12-22 IAEA
Operating Lic:
1988-03-22
First Criticality:
1988-03-08 IAEA
Grid Connection:
1988-03-30 IAEA
Commercial Op:
1988-08-25
License Renewed:
2017-09-28
License Exp:
2047-08-20
Market & Region
EIA market and grid-region classifications: NERC reliability region, U.S. Census region, balancing authority responsible for grid operations, and whether the unit operates as a rate-regulated utility or a competitive merchant generator. Hover any value for the full name.
NERC Region:
TRE
— Texas Regional Entity
Census Region:
WSC
— West South Central
Balancing Authority:
ERCO
— Electric Reliability Council of Texas (ERCOT) (ISO/RTO)
Market Structure:
Merchant
— Competitive generator selling into wholesale markets