Conowingo
Conowingo is a 531 MW hydroelectric power plant in Harford County, Maryland, operated by Constellation Power, Inc. EIA-860M lists 11 generating units here, inside PJM. Its units entered service between 1928 and 1964.
As of 2026-07 (inventory dated 2026-07-31) · EIA-860M Preliminary Monthly Electric Generator Inventory · eia.gov/…/july_generator2026.xlsx · eia.gov/…/eia860m
- Nameplate capacity
- 530.8 MW
- 496.9 MW net summer
- Generating units
- 11
- In service
- 1928–1964
- EIA plant ID
- 1574
Where it is
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- County
- Harford County, Maryland
- Coordinates
- 39.6572, -76.1752
- Balancing authority
- PJM
- Sector
- IPP Non-CHP
Units, technology and status
- Operator of record
- Constellation Power, Inc
- Primary energy source
- Hydro
- Technologies
- Conventional Hydroelectric
- Status
- Operating
Conowingo: FAQ
- Where is Conowingo?
- In Harford County, Maryland (MD). The map on this page is placed at the coordinates EIA files for the plant, which locate the site rather than any individual unit.
- How big is Conowingo?
- 531 MW of nameplate capacity across 11 units, as of the EIA-860M release for 2026-07.
- Who owns Conowingo?
- EIA-860M names Constellation Power, Inc as the reporting entity. That is the operator of record on the survey, which is not always the ultimate owner.
- Is this the same as Conowingo LLC?
- Probably, but EIA-860M does not say. The survey records a plant name and a reporting entity — Constellation Power, Inc here — not the project company that holds the asset. Project companies are commonly registered as an LLC carrying the plant's name, so a search for "Conowingo LLC" usually means this site. This page shows only what EIA files, and does not assert a corporate structure it cannot see.
- Is Conowingo still running?
- EIA-860M files it as "Operating" for 2026-07. Statuses change monthly, and this page follows the monthly release.