Calvert Cliffs 1
Online · 100% powerConstellation Energy·Lusby, MD·PWR·884 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.
221
Current Run
days
#31 of 95
Mid Quartile
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Longest recorded period of continuous operation between outages.
716
Record Run
days
#29 of 95
Mid Quartile
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Breaker-to-Breaker runs — continuous operation exceeding the cycle-adjusted threshold (623 days for this 24-month cycle unit) with no trips to 0% power.
4
B2B Runs
#50 of 86
Mid 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.
93.2%
Capacity Factor
#13 of 95
Top 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.
14.95 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.
6
Scrams
#42 of 94
Mid Quartile
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Years since commercial operation began. License remaining: 7.8 years.
51.5
Operating Age
years
7.8 yrs remaining
Excellence Score, Records & Plant Facts
Breaker-to-Breaker Runs 4 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.
Calvert Cliffs 1 has logged 4 breaker-to-breaker runs, continuous stretches from one refueling to the next with no trip to zero power. Its longest ran 714 days, and its runs average 685 days.
714
Best Run (days)
CC1R26 (2022-02-28) → CC1R27 (2024-02-12)
685
Avg Run (days)
★ Quadruple breaker-to-breaker
CC1R23 → CC1R24 → CC1R25 → CC1R26 → CC1R27
All Runs
| 2022-02-28 | 2024-02-12 | 714 days | CC1R26 → CC1R27 |
| 2020-03-13 | 2022-02-07 | 696 days | CC1R25 → CC1R26 |
| 2018-03-17 | 2020-02-17 | 702 days | CC1R24 → CC1R25 |
| 2016-06-02 | 2018-02-19 | 627 days | CC1R23 → CC1R24 |
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: Calvert Cliffs Nuclear Power Plant.
Calvert Cliffs Nuclear Power Plant is a two-unit nuclear station on the western shore of Chesapeake Bay near Lusby, in Calvert County, Maryland, about 40 miles south of Annapolis.
Read more
Construction began on June 1, 1968, and both units use Combustion Engineering two-loop pressurized water reactors. Unit 1 was first connected to the grid on January 3, 1975, and entered commercial operation on May 8, 1975. Unit 2 was connected on December 7, 1976, and entered commercial operation on April 1, 1977. In 1971 the D.C. Circuit's decision in Calvert Cliffs' Coordinating Committee v. AEC required the Atomic Energy Commission to weigh environmental impacts in its licensing under the National Environmental Policy Act.
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.
Calvert Cliffs 1 has operated for about 51.5 years and averaged a 93.2% lifetime capacity factor, generating roughly 199.6 TWh of electricity. Its longest unbroken run reached 716 days.
Lifecycle & Tenure
Operating Age: 51.5 Yrs
Build Time: 5.8 Yrs
Lic. Remaining: 7.8 Yrs
Production & Power
Lifetime CF: 93.2%
Efficiency: 32.3%
Generated: 199.6 TWh
Reliability & Outages
Record Run: 716 Days
Refuelings: 14
Avg Startup: 3.4 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 |
|---|---|---|---|
| Nov 6, 2009 | Ownership stake | Constellation Energy | Constellation Energy Nuclear Group (Constellation / EDF) |
| Mar 12, 2012 | Merger | Constellation Energy (with EDF) | Exelon (with EDF) |
| Apr 1, 2014 | Operator change | Constellation Energy Nuclear Group (operator) | Exelon (took over operation) |
| Aug 6, 2021 | Ownership stake | Exelon and EDF | Exelon |
| Feb 1, 2022 | Spin-off | Exelon | Constellation Energy |
CEG
Constellation Energy Corporation
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Operational Excellence Score Subscribers
Calvert Cliffs 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 6 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.
Calvert Cliffs 1 has recorded 6 reactor scrams, or emergency shutdowns, since 2011 (5 automatic, 1 manual). On average the unit was back to full power about 3.8 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:
COMB CE
Turbine Supplier:
GENERAL ELECTRIC CO. IAEA
Thermal Power:
2737 MWt
Net Capacity:
884 MWe
Gross Capacity:
918 MWe IAEA
Design Capacity:
845 MWe IAEA
Efficiency:
32.3%
Status:
Operating
Lifetime Output:
317.1 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 #:
05000317
License #:
DPR-53
License Type:
OL-FP
Const. Permit:
1969-07-07
Construction Start:
1968-06-01 IAEA
Operating Lic:
1974-07-31
First Criticality:
1974-10-07 IAEA
Grid Connection:
1975-01-03 IAEA
Commercial Op:
1975-05-08
License Renewed:
2000-03-23
License Exp:
2034-07-31
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:
RFC
— Reliability First Corporation
Census Region:
SAT
— South Atlantic
Balancing Authority:
PJM
— PJM Interconnection (ISO/RTO)
Market Structure:
Merchant
— Competitive generator selling into wholesale markets