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Conowingo

Constellation Energy Generation, LLC - Harford County - PJM

Conowingo is an EIA-anchored 530.8 MW, 11-unit hydroelectric station on Maryland's lower Susquehanna River. Constellation identifies itself as the plant owner and operator and says the station has operated since 1928.

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Overview

Nameplate capacity: 530.8 MW
Canonical EIA plant baseline.
Registry anchor: Plant 1574
plant-1574

Structured profile

Technology: Conventional Hydroelectric
Operator: Constellation Energy Generation, LLC

Conowingo

PJM · Asset profile

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Conowingo — 531 MW hydro plant, Harford County, MD · Ask the Grid

Units and generators

Operating generator records and technology attributes reported through EIA-860.

Generator	Capacity	Technology	Operation	Status
1	45 MW 41 MW summer	Conventional Hydroelectric Water · HY	—	Operating
10	55.6 MW 56.1 MW summer	Conventional Hydroelectric Water · HY	May 1964	Operating
11	55.6 MW 52 MW summer	Conventional Hydroelectric Water · HY	May 1964	Operating
2	36 MW 32.7 MW summer	Conventional Hydroelectric Water · HY	—	Operating
3	48 MW 41.9 MW summer	Conventional Hydroelectric Water · HY	—	Operating
4	47.7 MW 41.9 MW summer	Conventional Hydroelectric Water · HY	—	Operating
5	36 MW 32.7 MW summer	Conventional Hydroelectric Water · HY	—	Operating
6	47.7 MW 42.3 MW summer	Conventional Hydroelectric Water · HY	—	Operating
7	48 MW 42.3 MW summer	Conventional Hydroelectric Water · HY	—	Operating
8	55.6 MW 56.7 MW summer	Conventional Hydroelectric Water · HY	Mar 1964	Operating
9	55.6 MW 57.3 MW summer	Conventional Hydroelectric Water · HY	Mar 1964	Operating

Commercial, land, and environmental record

Source-backed project transactions, agreements, land records, permits, and environmental disclosures. Portfolio and adjacent-project facts remain explicitly scoped.

Transactions and agreements

Regulatory Approval

Jan 1, 1926

The Federal Power Commission issued a license to Susquehanna Power Company and Philadelphia Electric Company to construct the Conowingo Hydroelectric Project.

Federal Power Commission · Susquehanna Power Company · Philadelphia Electric Company

mde.maryland.gov

Commercial Operation

Mar 1, 1928

Seven 36-MW Francis turbines (Units 1–7) entered commercial operation at Conowingo Dam. The dam had been built with space for four additional turbine units.

Susquehanna Power Company · Philadelphia Electric Company

mde.maryland.gov

Generation Expansion

Jan 1, 1965

Four additional Kaplan-type units (Units 8–11) entered commercial operation, increasing total station capacity to approximately 514.4 MW including the two house units.

Susquehanna Power Company · Philadelphia Electric Company

mde.maryland.gov

Structural Upgrade

Jan 1, 1976

Tendon anchors were installed through the dam into bedrock to strengthen the structure to withstand overtopping from high river flows.

Conowingo operators

mde.maryland.gov

Regulatory Approval

Jan 1, 1980

Conowingo received a new license from FERC, extending operations through 2014.

Federal Energy Regulatory Commission · Conowingo operators

mde.maryland.gov

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.

Parties and identifiers

OrganizationRoleBasis

plant:plant-1574Grid selectionCanonical asset page /assets/facilities/conowingo.

Reporting portfolio

EIA reporting entity

Constellation Power, Inc

Entity 6035

Operating portfolio

17 plants

4 states

Reported capacity

7,734.1 MW

Conventional Hydroelectric · Hydroelectric Pumped Storage · Natural Gas Fired Combined Cycle

Largest reported plants in this portfolio
Largest reported plants	Capacity	State
Handley	1,314.8 MW	TX
Wolf Hollow II	1,231.2 MW	TX
Colorado Bend II	1,230.3 MW	TX
Muddy Run	1,072 MW	PA
Eddystone Generating Station	861.6 MW	PA
Croydon CT Generating Station	546.4 MW	PA
ConowingoCurrent	530.8 MW	MD
Exelon West Medway II LLC	263.6 MW	MA

Portfolio membership follows the latest EIA-860 reporting entity. It does not imply ultimate ownership.

View full reporting portfolio

Timeline and sources

Project milestones and public references behind the asset profile.

Project timeline

Jan 1, 1926
Jan 1, 1926
Federal construction license issuedmde.marylan...
The Federal Power Commission issued a license to Susquehanna Power Company and Philadelphia Electric Company to construct the Conowingo Hydroelectric Project.
Mar 1, 1928
Mar 1, 1928
Commercial Operation Beganmde.marylan...
Seven 36-MW Francis turbines (Units 1–7) entered commercial operation at Conowingo Dam. The dam had been built with space for four additional turbine units.
Mar 1964
Mar 1964
Generators enter operationEIA-860
EIA-860 lists generator 8, generator 9 with this operating date.
View 16 more milestonesHide 16 milestones
1. May 1964
  May 1964
  Generators enter operationEIA-860
  EIA-860 lists generator 10, generator 11 with this operating date.
2. Jan 1, 1965
  Jan 1, 1965
Dec 1, 2022
Dec 1, 2022
2021 license vacated on appealsec.gov
The 50-year FERC license issued on March 19, 2021 was vacated after judicial review. Environmental groups challenged the license, and the U.S. Court of Appeals for the D.C. Circuit vacated FERC's decision to grant the license, remanding it back to FERC for further proceedings.
Dec 1, 2022
Dec 1, 2022
Annual license status (post-vacatur)sec.gov
Upon issuance of the mandate from the U.S. Court of Appeals for the D.C. Circuit, Constellation began operating the Conowingo Hydroelectric Project under an automatically renewing annual license containing the same terms as the license that was in effect prior to the 2021 FERC order.
Oct 2, 2025
Oct 2, 2025
Revised water-quality certification and historic settlement agreementmde.marylan...
Constellation Energy Generation, LLC, Maryland Department of the Environment, Waterkeepers Chesapeake, and Lower Susquehanna Riverkeeper Association reached a revised settlement agreement. The Maryland Department of the Environment issued Revised Water Quality Certification 17-WQC-02(R1), valued at more than $340 million in commitments over the next 50 years. The agreement includes operational flow modifications, $87.6 million for water quality and resiliency initiatives, fish and eel passage improvements, debris removal, freshwater mussel restoration, invasive species control, and funding for additional dredging studies.

Sources

PublisherReferenceType

U.S. Energy Information AdministrationEIA-860 generator inventoryFederal registry

U.S. Energy Information AdministrationEIA-923 generation filingsFederal filing

mde.maryland.govmde.maryland.govauthoritative

Common questions about Conowingo

Answered from the published record above. Questions whose inputs this profile does not carry are omitted rather than estimated.

How big is Conowingo?

Conowingo has a reported capacity of 530.8 MW. Source: EIA Form 860M.

What kind of plant is Conowingo?

Conowingo is a Conventional Hydroelectric facility in Harford County, MD, participating in the PJM market.

Where is Conowingo located?

Conowingo is in Harford County, MD, inside the PJM balancing area.

Who operates Conowingo?

Conowingo is operated by Constellation Power, Inc according to the EIA generator inventory. Reporting membership does not by itself establish ultimate ownership.

How much electricity does Conowingo generate?

Conowingo reported 1,684.4 GWh over the twelve months to 2026-04. Figures are net generation as filed to EIA-923.

How does Conowingo compare to other plants?

By capacity, Conowingo ranks #26 of 1,349 operating plants of the same technology nationally. It ranks #1 of 2 in MD.

Co-located assets

Plants within 25 km, nearest first, regardless of technology. Proximity is straight-line distance between mapped plant coordinates; it does not by itself establish a shared point of interconnection.

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Conowingo

Overview

Structured profile

Ask about Conowingo

Conowingo

Overview

Structured profile

Ask about Conowingo

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Units and generators

Performance

Peer context

Monthly generation

Grid and market context

Nearby substations

Commercial, land, and environmental record

Transactions and agreements

Related parties and identifiers

Parties and identifiers

Reporting portfolio

Timeline and sources

Project timeline

Sources

Common questions about Conowingo

How big is Conowingo?

What kind of plant is Conowingo?

Where is Conowingo located?

Who operates Conowingo?

How much electricity does Conowingo generate?

How does Conowingo compare to other plants?

Co-located assets