# Muddy Run

PJM Hydroelectric Pumped Storage · https://askthegrid.com/assets/facilities/muddy-run

Muddy Run is a battery energy storage facility with 1,072 MW of EIA-reported nameplate capacity and 10,720 MWh of reported energy capacity in Lancaster County, Pennsylvania, registered as EIA Plant ID 3164. Constellation Energy is the public owner or developer; Constellation Power, Inc is the registered plant entity or operator. Muddy Run was the largest pumped-storage hydroelectric power plant in the world when it began commercial operation. The plant began commercial operation in 1966. The facility interconnects at PECO EMAAC at 230 kV.
PECO EMAAC · 230 kV.

## Key facts

- Technology: Hydroelectric Pumped Storage
- Power capacity: 1072 MW
- Commercial operation: 1966
- Operating status: operating

## Grid and market context

- ISO/RTO: PJM
- Balancing authority: PJM
- Interconnection voltage: 230 kV

## Source-backed facts

- Owner logo domain: constellationenergy.com — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: high
- Identifiers: [{"value":"3164","system":"EIA plant ID"},{"value":"P-2355","system":"FERC hydropower project number"},{"value":"PJM","system":"PJM balancing authority / power market"},{"value":"MUDDY RUN 1","system":"PJM RPM resource"}] — Source · confidence: medium
- Identifiers: [{"value":"3164","system":"EIA plant ID"},{"value":"P-2355","system":"FERC hydropower project number"},{"value":"PJM","system":"PJM balancing authority / power market"},{"value":"MUDDY RUN 1","system":"PJM RPM resource"}] — Sheet1 · confidence: medium
- Description: Muddy Run is an operational pumped-storage hydroelectric plant in Lancaster County, Pennsylvania. The plant has eight generating units with 1,072 MW of total nameplate capacity and participates in the PJM market. Constellation describes the facility as owned and operated by Constellation, with commercial operation beginning in 1966. — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: medium
- Identifiers.1: {"value":"P-2355","system":"FERC hydropower project number"} — Source · confidence: high
- Identifiers.3: {"value":"MUDDY RUN 1","system":"PJM RPM resource"} — Sheet1 · confidence: medium
- Parties.0: {"relationship":"Owner and parent operator","name":"Constellation Energy","official_url":"https://www.constellationenergy.com/"} — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: high
- Parties.2: {"relationship":"Historical FERC licensee","name":"Exelon Generation Company, LLC","official_url":null} — Source · confidence: medium
- Unit configuration: Eight reversible pumped-storage hydroelectric turbine-generator units, 134 MW each, totaling 1,072 MW. — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: medium
- Commercial operation date: 1966 — Source · confidence: medium
- Unit count: 8 — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: high
- Construction scope: Muddy Run is an operational pumped-storage hydroelectric facility comprising a dam across the Muddy Run ravine, an upper reservoir, a powerhouse, and eight reversible generating/pumping units. Water flows from the upper reservoir through the turbines to Conowingo Pond, and the units operate as pumps to refill the upper reservoir. The plant entered commercial operation in 1966; its turbines and generators were later refurbished, with rehabilitation and modernization reported during 1992–1996 and 1998–2000. The owner reports 1,070 MW from eight units, while the EIA-based plant record reports 1,072 MW total nameplate capacity. Installed equipment identified in the sources includes eight Francis turbines rated at 138 MW each and eight electric generators. — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: medium
- Construction scope: Muddy Run is an operational pumped-storage hydroelectric facility comprising a dam across the Muddy Run ravine, an upper reservoir, a powerhouse, and eight reversible generating/pumping units. Water flows from the upper reservoir through the turbines to Conowingo Pond, and the units operate as pumps to refill the upper reservoir. The plant entered commercial operation in 1966; its turbines and generators were later refurbished, with rehabilitation and modernization reported during 1992–1996 and 1998–2000. The owner reports 1,070 MW from eight units, while the EIA-based plant record reports 1,072 MW total nameplate capacity. Installed equipment identified in the sources includes eight Francis turbines rated at 138 MW each and eight electric generators. — Power plant profile: Muddy Run Pumped Storage Plant, US · confidence: medium
- Product url: https://www.voith.com/corp-en/products-services/hydropower-components/turbines.html — Power plant profile: Muddy Run Pumped Storage Plant, US · confidence: medium
- Product url: https://www.voith.com/corp-en/products-services/hydropower-components/turbines.html — Turbines & shut-off valves | Voith · confidence: medium
- Kind: hydro — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: high
- Quality notes: ["The EIA-derived plant record reports 1,072 MW of total nameplate capacity, while Constellation's facility page reports 1,070 MW; this directory uses the EIA value.","Commercial-operation reporting distinguishes between milestones: Constellation states that commercial operation began in 1966, while a project filing reports that units 1–6 began operation at various points in 1967; the powerhouse was completed in 1968.","No standalone project sale, project-specific financing instrument, expansion, or retirement is disclosed in the cited material. The 2012 Exelon–Constellation merger and the 2022 separation were corporate ownership transactions rather than identified Muddy Run sale or project-financing transactions."] — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: medium
- Quality notes: ["The EIA-derived plant record reports 1,072 MW of total nameplate capacity, while Constellation's facility page reports 1,070 MW; this directory uses the EIA value.","Commercial-operation reporting distinguishes between milestones: Constellation states that commercial operation began in 1966, while a project filing reports that units 1–6 began operation at various points in 1967; the powerhouse was completed in 1968.","No standalone project sale, project-specific financing instrument, expansion, or retirement is disclosed in the cited material. The 2012 Exelon–Constellation merger and the 2022 separation were corporate ownership transactions rather than identified Muddy Run sale or project-financing transactions."] — muddy run pumped storage project (ferc no. 2355) - Exelon... · confidence: medium
- Financing summary: No project-specific debt, tax-equity financing, or other financing facility is disclosed in the cited project records. Separately, Exelon completed an all-stock merger with Constellation on 2012-03-12; Exelon's SEC filing reports estimated consideration of $7.365 billion, while the merger announcement described approximately $7.9 billion of total equity value. Those amounts were corporate merger consideration, not Muddy Run project financing or standalone sale proceeds. — Source · confidence: medium
- Commercial parties.0: {"relationship":"Current owner and parent operator","name":"Constellation Energy","detail":"Constellation identifies Muddy Run as owned and operated by Constellation and currently operates the facility as part of its generation portfolio.","official_url":"https://www.constellationenergy.com/"} — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: medium
- Quality notes.0: The EIA-derived plant record reports 1,072 MW of total nameplate capacity, while Constellation's facility page reports 1,070 MW; this directory uses the EIA value. — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: high
- Quality notes.1: Commercial-operation reporting distinguishes between milestones: Constellation states that commercial operation began in 1966, while a project filing reports that units 1–6 began operation at various points in 1967; the powerhouse was completed in 1968. — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: high
- Quality notes.2: No standalone project sale, project-specific financing instrument, expansion, or retirement is disclosed in the cited material. The 2012 Exelon–Constellation merger and the 2022 separation were corporate ownership transactions rather than identified Muddy Run sale or project-financing transactions. — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: high
- Quality notes.2: No standalone project sale, project-specific financing instrument, expansion, or retirement is disclosed in the cited material. The 2012 Exelon–Constellation merger and the 2022 separation were corporate ownership transactions rather than identified Muddy Run sale or project-financing transactions. — muddy run pumped storage project (ferc no. 2355) - Exelon... · confidence: high
- Timeline.1: {"event":"Commercial operation began","date":"1966","detail":"Constellation states that Muddy Run began providing electric power to the regional transmission system in 1966."} — muddy run pumped storage project (ferc no. 2355) - Exelon... · confidence: high
- Timeline.2: {"event":"Initial generating units entered service","date":"1967","detail":"A Muddy Run project filing reports that units 1–6 began commercial operation at various points during 1967."} — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: high
- Timeline.3: {"event":"Powerhouse construction completed","date":"1968","detail":"Muddy Run's powerhouse construction was completed in 1968."} — muddy run pumped storage project (ferc no. 2355) - Exelon... · confidence: high
- Timeline.7: {"event":"Generation business separated from Exelon","date":"2022-02-02","detail":"Exelon completed the separation of Constellation, its former power-generation and competitive-energy business. Constellation launched as a standalone publicly traded company."} — Muddy Run Pumped Storage Facility | Constellation Energy Locations · confidence: high
- Interconnection voltage kv: 230 — PJM Manual 03: · confidence: medium

## Timeline

- 1966 — Commercial operation began
  Constellation states that Muddy Run began providing electric power to the regional transmission system in 1966.
  Source: Muddy Run Pumped Storage Facility | Constellation Energy Locations (https://www.constellationenergy.com/about/locations/muddy-run-pumped-storage-facility.html)
- 2012-03-12 — Exelon–Constellation corporate merger
  Exelon completed its merger with Constellation Energy Group, Inc.; Constellation became a wholly owned Exelon subsidiary before related internal restructuring. The cited records do not identify Muddy Run as a separately sold project.
  Source: Source (https://investors.exeloncorp.com/static-files/47bff82b-af58-4202-ac6a-6a19b461757a)
- 2016 — FERC license renewal
  Constellation received a 40-year FERC license renewal for continued operation of Muddy Run through 2055.
  Source: Muddy Run Pumped Storage Facility | Constellation Energy Locations (https://www.constellationenergy.com/about/locations/muddy-run-pumped-storage-facility.html)
- 2022-02-02 — Generation business separated from Exelon
  Exelon completed the separation of Constellation, its former power-generation and competitive-energy business. Constellation launched as a standalone publicly traded company.
  Source: Exelon Completes Separation of Constellation, Moving Forward as Nation’s Premier Transmission and Distribution Utility Company (https://www.exeloncorp.com/newsroom/exelon-completes-separation-of-constellation)
- undated — Turbine and generator refurbishment
  Constellation reports that the original general plant configuration remains and that the turbines and generators have been refurbished; no specific refurbishment date is given.
  Source: Muddy Run Pumped Storage Facility | Constellation Energy Locations (https://www.constellationenergy.com/about/locations/muddy-run-pumped-storage-facility.html)

## Sources

- [Muddy Run Pumped Storage Facility | Constellation Energy Locations](https://www.constellationenergy.com/about/locations/muddy-run-pumped-storage-facility.html) — constellationenergy.com · tier other
- [Richard Glick, Chairman](https://www.ferc.gov/sites/default/files/2021-03/H-1-P-405-106.pdf) — ferc.gov · tier regulatory
- [Sheet1](https://www.pjm.com/-/media/DotCom/markets-ops/rpm/rpm-auction-info/2025-2026/2025-2026-rpm-existing-resource-list-post.xlsx) — pjm.com · tier other
- [Source](https://constellationenergy.com/about/locations/muddy-run-pumped-storage-facility.html) — constellationenergy.com · tier other
- [Power plant profile: Muddy Run Pumped Storage Plant, US](https://www.power-technology.com/data-insights/power-plant-profile-muddy-run-pumped-storage-plant-us/) — power-technology.com · tier other
- [Turbines & shut-off valves | Voith](https://www.voith.com/corp-en/products-services/hydropower-components/turbines.html) — voith.com · tier other
- [muddy run pumped storage project (ferc no. 2355) - Exelon ...](https://www.yumpu.com/en/document/view/5991304/muddy-run-pumped-storage-project-ferc-no-2355-exelon-) — yumpu.com · tier other
- [Source](https://investors.exeloncorp.com/static-files/47bff82b-af58-4202-ac6a-6a19b461757a) — investors.exeloncorp.com · tier other
- [Source](https://investors.exeloncorp.com/static-files/39c1737f-3903-447a-806b-180c8109b5cc) — investors.exeloncorp.com · tier other
- [Exelon Completes Separation of Constellation, Moving Forward as Nation’s Premier Transmission and Distribution Utility Company](https://www.exeloncorp.com/newsroom/exelon-completes-separation-of-constellation) — exeloncorp.com · tier other
- [FERC approves Exelon acquisition of Constellation Energy](https://www.renewableenergyworld.com/energy-business/policy-and-regulation/ferc-approves-exelon/) — renewableenergyworld.com · tier other
- [ceg-20221231](https://www.sec.gov/Archives/edgar/data/1868275/000186827523000014/ceg-20221231.htm) — sec.gov · tier regulatory
- [PJM Manual 03:](https://www.pjm.com/-/media/DotCom/documents/manuals/m03.pdf) — pjm.com · tier other

## Data quality

- The EIA-derived plant record reports 1,072 MW of total nameplate capacity, while Constellation's facility page reports 1,070 MW; this directory uses the EIA value. No standalone project sale, project-specific financing instrument, expansion, or retirement is disclosed in the cited material. The 2012 Exelon–Constellation merger and the 2022 separation were corporate ownership transactions rather than identified Muddy Run sale or project-financing transactions.

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Canonical page: https://askthegrid.com/assets/facilities/muddy-run

Source: Ask the Grid — https://askthegrid.com/