# Watson Cogeneration

CAISO Natural Gas Fired Combined Cycle · https://askthegrid.com/assets/facilities/watson-cogeneration

Watson Cogeneration is a natural gas-fired power facility with 405 MW of EIA-reported nameplate capacity in Los Angeles County, California, registered as EIA Plant ID 50216. ARCO Products Co-Watson is the registered plant entity or operator. Marathon Petroleum identifies the Watson cogeneration plant as the largest cogeneration facility in California; its refinery page states that the plant produces approximately 400 MW. Commercial operation began on April 1, 1988.

## Key facts

- Technology: Natural Gas Fired Combined Cycle
- Power capacity: 405 MW
- Operating status: operating

## Grid and market context

- ISO/RTO: CAISO
- Balancing authority: CAISO (CISO)
- Substation: SCE Hinson Substation
- Point of interconnection: SCE Hinson Substation
- Transmission owner: Southern California Edison (SCE)
- Interconnection voltage: 66 kV

## Source-backed facts

- Owner logo domain: marathonpetroleum.com — Los Angeles Refinery | Marathon Petroleum Refineries · confidence: medium
- Owner logo domain: marathonpetroleum.com — mpc-20220630 · confidence: medium
- Identifiers: [{"value":"50216","system":"EIA plant ID"},{"value":"867","system":"EIA utility ID"},{"value":"GN91, GN92, GN93, GN94, GN95, GN96","system":"EIA generator IDs"},{"value":"85-AFC-01; 85-AFC-01C","system":"California Energy Commission docket"},{"value":"85-526-001","system":"FERC cogeneration docket"},{"value":"CISO / CAISO","system":"Balancing authority / ISO"},{"value":"ARCOGN_2_UNITS","system":"CAISO resource identifier"},{"value":"POD_ARCOGN_2_UNITS","system":"CAISO POD"}] — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Identifiers: [{"value":"50216","system":"EIA plant ID"},{"value":"867","system":"EIA utility ID"},{"value":"GN91, GN92, GN93, GN94, GN95, GN96","system":"EIA generator IDs"},{"value":"85-AFC-01; 85-AFC-01C","system":"California Energy Commission docket"},{"value":"85-526-001","system":"FERC cogeneration docket"},{"value":"CISO / CAISO","system":"Balancing authority / ISO"},{"value":"ARCOGN_2_UNITS","system":"CAISO resource identifier"},{"value":"POD_ARCOGN_2_UNITS","system":"CAISO POD"}] — Curtailed and Non-Operational Generator AM Report Apr... · confidence: medium
- Identifiers: [{"value":"50216","system":"EIA plant ID"},{"value":"867","system":"EIA utility ID"},{"value":"GN91, GN92, GN93, GN94, GN95, GN96","system":"EIA generator IDs"},{"value":"85-AFC-01; 85-AFC-01C","system":"California Energy Commission docket"},{"value":"85-526-001","system":"FERC cogeneration docket"},{"value":"CISO / CAISO","system":"Balancing authority / ISO"},{"value":"ARCOGN_2_UNITS","system":"CAISO resource identifier"},{"value":"POD_ARCOGN_2_UNITS","system":"CAISO POD"}] — Source_Sink_Update · confidence: medium
- Official project url: https://www.energy.ca.gov/powerplant/combined-cycle/watson-cogeneration-project — Watson Cogeneration Project | California Energy Commission · confidence: high
- Description: Watson Cogeneration is a 405-MW natural-gas combined-cycle cogeneration plant in Carson, Los Angeles County, California. The plant has six generating units, with the first unit entering service in 1987, and is operated by ARCO Products Co-Watson. Its cogenerated electricity is sold to Southern California Edison, while process steam is supplied to the adjacent refinery. — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Parties: [{"relationship":"Project owner","name":"Watson Cogeneration Company","official_url":null},{"relationship":"Parent owner","name":"Marathon Petroleum Corporation","official_url":"https://www.marathonpetroleum.com/"},{"relationship":"Operator / EIA utility","name":"ARCO Products Co-Watson","official_url":"https://www.marathonpetroleum.com/Operations/Refining/Los-Angeles-Refinery/"},{"relationship":"Power off-taker","name":"Southern California Edison Company","official_url":"https://www.sce.com/"},{"relationship":"Project support / services provider","name":"NAES Corporation","official_url":"https://www.naes.com/"},{"relationship":"Former 49% co-owner through June 2022","name":"NRG Energy, Inc.","official_url":"https://www.nrg.com/"}] — mpc-20220630 · confidence: medium
- Parties: [{"relationship":"Project owner","name":"Watson Cogeneration Company","official_url":null},{"relationship":"Parent owner","name":"Marathon Petroleum Corporation","official_url":"https://www.marathonpetroleum.com/"},{"relationship":"Operator / EIA utility","name":"ARCO Products Co-Watson","official_url":"https://www.marathonpetroleum.com/Operations/Refining/Los-Angeles-Refinery/"},{"relationship":"Power off-taker","name":"Southern California Edison Company","official_url":"https://www.sce.com/"},{"relationship":"Project support / services provider","name":"NAES Corporation","official_url":"https://www.naes.com/"},{"relationship":"Former 49% co-owner through June 2022","name":"NRG Energy, Inc.","official_url":"https://www.nrg.com/"}] — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Parties: [{"relationship":"Project owner","name":"Watson Cogeneration Company","official_url":null},{"relationship":"Parent owner","name":"Marathon Petroleum Corporation","official_url":"https://www.marathonpetroleum.com/"},{"relationship":"Operator / EIA utility","name":"ARCO Products Co-Watson","official_url":"https://www.marathonpetroleum.com/Operations/Refining/Los-Angeles-Refinery/"},{"relationship":"Power off-taker","name":"Southern California Edison Company","official_url":"https://www.sce.com/"},{"relationship":"Project support / services provider","name":"NAES Corporation","official_url":"https://www.naes.com/"},{"relationship":"Former 49% co-owner through June 2022","name":"NRG Energy, Inc.","official_url":"https://www.nrg.com/"}] — Energy Service Provider - NAES · confidence: medium
- Canonical name: Watson Cogeneration — Watson Cogeneration Project | California Energy Commission · confidence: high
- Identifiers.3: {"value":"85-AFC-01; 85-AFC-01C","system":"California Energy Commission docket"} — Watson Cogeneration Project | California Energy Commission · confidence: high
- Identifiers.6: {"value":"ARCOGN_2_UNITS","system":"CAISO resource identifier"} — Curtailed and Non-Operational Generator AM Report Apr... · confidence: medium
- Identifiers.7: {"value":"POD_ARCOGN_2_UNITS","system":"CAISO POD"} — Source_Sink_Update · confidence: medium
- Parties.1: {"relationship":"Parent owner","name":"Marathon Petroleum Corporation","official_url":"https://www.marathonpetroleum.com/"} — mpc-20220630 · confidence: high
- Parties.1: {"relationship":"Parent owner","name":"Marathon Petroleum Corporation","official_url":"https://www.marathonpetroleum.com/"} — Los Angeles Refinery | Marathon Petroleum Refineries · confidence: high
- Parties.3: {"relationship":"Power off-taker","name":"Southern California Edison Company","official_url":"https://www.sce.com/"} — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Parties.4: {"relationship":"Project support / services provider","name":"NAES Corporation","official_url":"https://www.naes.com/"} — Energy Service Provider - NAES · confidence: medium
- Parties.5: {"relationship":"Former 49% co-owner through June 2022","name":"NRG Energy, Inc.","official_url":"https://www.nrg.com/"} — mpc-20220630 · confidence: high
- Interconnection: SCE Hinson Substation, via a high-voltage transmission line; Southern California Edison Company is the connected utility/off-taker. — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Unit count: 6 — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Construction scope: Four parallel natural-gas combustion-turbine/HRSG trains and two parallel steam-turbine-driven power-generator trains, with associated auxiliaries, control room, electrical substation, and transmission line. The installed equipment identified in the sources is four GE Model 7EA gas turbines, four Vogt HRSGs, and two Dresser-Rand steam turbine generators. — Source · confidence: high
- Product url: https://www.gevernova.com/gas-power/products/gas-turbines/7e — 7E Gas Turbine (7E.03) | GE Vernova · confidence: high
- Kind: thermal — Source · confidence: high
- Description: Watson Cogeneration is a natural-gas combined-cycle cogeneration facility in Carson, Los Angeles County. The California Energy Commission describes the original 385-MW configuration as four combustion-turbine/heat-recovery-steam-generator trains and two steam-turbine generator trains; current plant records report six operational generating units totaling 405 MW. The facility supplies process steam to the adjacent refinery and sells electricity to Southern California Edison. It was certified in 1986, began commercial operation in 1988, and is now consolidated under Marathon Petroleum after MPC bought NRG Energy’s remaining 49% interest in June 2022. — Source · confidence: medium
- Description: Watson Cogeneration is a natural-gas combined-cycle cogeneration facility in Carson, Los Angeles County. The California Energy Commission describes the original 385-MW configuration as four combustion-turbine/heat-recovery-steam-generator trains and two steam-turbine generator trains; current plant records report six operational generating units totaling 405 MW. The facility supplies process steam to the adjacent refinery and sells electricity to Southern California Edison. It was certified in 1986, began commercial operation in 1988, and is now consolidated under Marathon Petroleum after MPC bought NRG Energy’s remaining 49% interest in June 2022. — Source · confidence: medium
- Quality notes: ["The CEC legacy project page reports 385 MW, while current EIA-derived plant records report 405 MW; these figures should not be treated as interchangeable without confirming the reporting boundary or later additions.","The 1997 45-MW fifth-train construction approval and the later 2012 fifth-train project are distinct regulatory actions. The 2012 project was terminated in 2015 and should not be counted as an operating expansion.","The disclosed $59 million Watson transaction and $2.635 billion NRG–Edison Mission Energy transaction are acquisition consideration, not project-level construction financing. No Watson-specific construction debt or project-financing terms were identified.","No retirement or repowering event was identified. A 2025 CEC amendment petition was docketed, but the filing described proposed changes rather than retirement or repowering."] — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Quality notes: ["The CEC legacy project page reports 385 MW, while current EIA-derived plant records report 405 MW; these figures should not be treated as interchangeable without confirming the reporting boundary or later additions.","The 1997 45-MW fifth-train construction approval and the later 2012 fifth-train project are distinct regulatory actions. The 2012 project was terminated in 2015 and should not be counted as an operating expansion.","The disclosed $59 million Watson transaction and $2.635 billion NRG–Edison Mission Energy transaction are acquisition consideration, not project-level construction financing. No Watson-specific construction debt or project-financing terms were identified.","No retirement or repowering event was identified. A 2025 CEC amendment petition was docketed, but the filing described proposed changes rather than retirement or repowering."] — Source · confidence: medium
- Quality notes: ["The CEC legacy project page reports 385 MW, while current EIA-derived plant records report 405 MW; these figures should not be treated as interchangeable without confirming the reporting boundary or later additions.","The 1997 45-MW fifth-train construction approval and the later 2012 fifth-train project are distinct regulatory actions. The 2012 project was terminated in 2015 and should not be counted as an operating expansion.","The disclosed $59 million Watson transaction and $2.635 billion NRG–Edison Mission Energy transaction are acquisition consideration, not project-level construction financing. No Watson-specific construction debt or project-financing terms were identified.","No retirement or repowering event was identified. A 2025 CEC amendment petition was docketed, but the filing described proposed changes rather than retirement or repowering."] — Source · confidence: medium
- Timeline: [{"event":"CEC certification","date":"1986-09-17","detail":"The California Energy Commission certified the original Watson Cogeneration Project under docket 85-AFC-01."},{"event":"Commercial operation","date":"1988-04-01","detail":"The original project began commercial operation."},{"event":"Initial ownership transfer","date":"1988-06-22","detail":"The CEC approved transfer of project ownership from ARCO Petroleum Products Company to Watson Cogeneration Company."},{"event":"Partial ownership transfer","date":"1997-01-30","detail":"The CEC approved transfer of 49% of the 51% share held by Products Cogeneration Company to Carson Cogeneration Company."},{"event":"45-MW fifth-train approval","date":"1997-10-17","detail":"The CEC approved construction of a new 45-MW fifth-train addition."},{"event":"Fifth-train project approval","date":"2012-04-11","detail":"The CEC approved Application for Certification 09-AFC-01C for an additional fifth train; the project was later terminated at the owner’s request."},{"event":"Upstream ownership change","date":"2014-04-30","detail":"The CEC received notice that NRG Energy had acquired Edison Mission Energy assets, including an interest in Watson Cogeneration."},{"event":"Fifth-train project termination","date":"2015-07-08","detail":"The CEC officially terminated the 09-AFC-01C fifth-train project at the owner’s request."},{"event":"Sale of remaining minority interest","date":"2022-06-01","detail":"MPC purchased Watson Cogeneration’s remaining 49% interest from NRG Energy for approximately $59 million and thereafter consolidated the entity."},{"event":"CEC amendment petition","date":"2025-07-03","detail":"The CEC docketed a Watson Cogeneration petition to amend the project; the filing stated that the proposed changes would not affect compliance and would have no significant environmental impacts."}] — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Timeline: [{"event":"CEC certification","date":"1986-09-17","detail":"The California Energy Commission certified the original Watson Cogeneration Project under docket 85-AFC-01."},{"event":"Commercial operation","date":"1988-04-01","detail":"The original project began commercial operation."},{"event":"Initial ownership transfer","date":"1988-06-22","detail":"The CEC approved transfer of project ownership from ARCO Petroleum Products Company to Watson Cogeneration Company."},{"event":"Partial ownership transfer","date":"1997-01-30","detail":"The CEC approved transfer of 49% of the 51% share held by Products Cogeneration Company to Carson Cogeneration Company."},{"event":"45-MW fifth-train approval","date":"1997-10-17","detail":"The CEC approved construction of a new 45-MW fifth-train addition."},{"event":"Fifth-train project approval","date":"2012-04-11","detail":"The CEC approved Application for Certification 09-AFC-01C for an additional fifth train; the project was later terminated at the owner’s request."},{"event":"Upstream ownership change","date":"2014-04-30","detail":"The CEC received notice that NRG Energy had acquired Edison Mission Energy assets, including an interest in Watson Cogeneration."},{"event":"Fifth-train project termination","date":"2015-07-08","detail":"The CEC officially terminated the 09-AFC-01C fifth-train project at the owner’s request."},{"event":"Sale of remaining minority interest","date":"2022-06-01","detail":"MPC purchased Watson Cogeneration’s remaining 49% interest from NRG Energy for approximately $59 million and thereafter consolidated the entity."},{"event":"CEC amendment petition","date":"2025-07-03","detail":"The CEC docketed a Watson Cogeneration petition to amend the project; the filing stated that the proposed changes would not affect compliance and would have no significant environmental impacts."}] — Source · confidence: medium
- Timeline: [{"event":"CEC certification","date":"1986-09-17","detail":"The California Energy Commission certified the original Watson Cogeneration Project under docket 85-AFC-01."},{"event":"Commercial operation","date":"1988-04-01","detail":"The original project began commercial operation."},{"event":"Initial ownership transfer","date":"1988-06-22","detail":"The CEC approved transfer of project ownership from ARCO Petroleum Products Company to Watson Cogeneration Company."},{"event":"Partial ownership transfer","date":"1997-01-30","detail":"The CEC approved transfer of 49% of the 51% share held by Products Cogeneration Company to Carson Cogeneration Company."},{"event":"45-MW fifth-train approval","date":"1997-10-17","detail":"The CEC approved construction of a new 45-MW fifth-train addition."},{"event":"Fifth-train project approval","date":"2012-04-11","detail":"The CEC approved Application for Certification 09-AFC-01C for an additional fifth train; the project was later terminated at the owner’s request."},{"event":"Upstream ownership change","date":"2014-04-30","detail":"The CEC received notice that NRG Energy had acquired Edison Mission Energy assets, including an interest in Watson Cogeneration."},{"event":"Fifth-train project termination","date":"2015-07-08","detail":"The CEC officially terminated the 09-AFC-01C fifth-train project at the owner’s request."},{"event":"Sale of remaining minority interest","date":"2022-06-01","detail":"MPC purchased Watson Cogeneration’s remaining 49% interest from NRG Energy for approximately $59 million and thereafter consolidated the entity."},{"event":"CEC amendment petition","date":"2025-07-03","detail":"The CEC docketed a Watson Cogeneration petition to amend the project; the filing stated that the proposed changes would not affect compliance and would have no significant environmental impacts."}] — Source · confidence: medium
- Commercial parties: [{"relationship":"Current project owner","name":"Watson Cogeneration Company","detail":"The project owner named in CEC regulatory filings; the entity is consolidated by Marathon Petroleum following MPC’s 2022 purchase of the remaining NRG interest.","official_url":null},{"relationship":"Parent owner / consolidated owner","name":"Marathon Petroleum Corporation","detail":"MPC purchased the remaining 49% interest in Watson Cogeneration from NRG Energy on June 1, 2022, for approximately $59 million.","official_url":"https://www.marathonpetroleum.com/"},{"relationship":"Operator / EIA utility","name":"ARCO Products Co-Watson","detail":"The EIA utility associated with plant ID 50216 and the Watson Cogeneration operating record.","official_url":"https://www.marathonpetroleum.com/Operations/Refining/Los-Angeles-Refinery/"},{"relationship":"Former 49% owner and seller","name":"NRG Energy, Inc.","detail":"NRG held the remaining 49% interest in Watson Cogeneration until selling it to MPC on June 1, 2022. NRG obtained the interest through its acquisition of Edison Mission Energy assets.","official_url":"https://www.nrg.com/"},{"relationship":"Predecessor project owner","name":"ARCO Petroleum Products Company","detail":"The original project owner from which ownership was transferred to Watson Cogeneration Company by CEC approval in June 1988.","official_url":null},{"relationship":"Predecessor portfolio owner / seller to NRG","name":"Edison Mission Energy","detail":"EME was the predecessor portfolio owner whose assets and subsidiary interests, including an interest in Watson Cogeneration, were acquired by NRG.","official_url":null},{"relationship":"Historical co-owner","name":"Products Cogeneration Company","detail":"Held a 51% share before the CEC-approved 1997 transfer of 49% of that share to Carson Cogeneration Company.","official_url":null},{"relationship":"Historical co-owner","name":"Carson Cogeneration Company","detail":"Received the CEC-approved transfer of 49% of the 51% share held by Products Cogeneration Company in January 1997.","official_url":null},{"relationship":"Power off-taker","name":"Southern California Edison Company","detail":"The CEC states that electricity generated by the project is sold to Southern California Edison through a high-voltage transmission connection.","official_url":"https://www.sce.com/"}] — Source · confidence: medium
- Commercial parties: [{"relationship":"Current project owner","name":"Watson Cogeneration Company","detail":"The project owner named in CEC regulatory filings; the entity is consolidated by Marathon Petroleum following MPC’s 2022 purchase of the remaining NRG interest.","official_url":null},{"relationship":"Parent owner / consolidated owner","name":"Marathon Petroleum Corporation","detail":"MPC purchased the remaining 49% interest in Watson Cogeneration from NRG Energy on June 1, 2022, for approximately $59 million.","official_url":"https://www.marathonpetroleum.com/"},{"relationship":"Operator / EIA utility","name":"ARCO Products Co-Watson","detail":"The EIA utility associated with plant ID 50216 and the Watson Cogeneration operating record.","official_url":"https://www.marathonpetroleum.com/Operations/Refining/Los-Angeles-Refinery/"},{"relationship":"Former 49% owner and seller","name":"NRG Energy, Inc.","detail":"NRG held the remaining 49% interest in Watson Cogeneration until selling it to MPC on June 1, 2022. NRG obtained the interest through its acquisition of Edison Mission Energy assets.","official_url":"https://www.nrg.com/"},{"relationship":"Predecessor project owner","name":"ARCO Petroleum Products Company","detail":"The original project owner from which ownership was transferred to Watson Cogeneration Company by CEC approval in June 1988.","official_url":null},{"relationship":"Predecessor portfolio owner / seller to NRG","name":"Edison Mission Energy","detail":"EME was the predecessor portfolio owner whose assets and subsidiary interests, including an interest in Watson Cogeneration, were acquired by NRG.","official_url":null},{"relationship":"Historical co-owner","name":"Products Cogeneration Company","detail":"Held a 51% share before the CEC-approved 1997 transfer of 49% of that share to Carson Cogeneration Company.","official_url":null},{"relationship":"Historical co-owner","name":"Carson Cogeneration Company","detail":"Received the CEC-approved transfer of 49% of the 51% share held by Products Cogeneration Company in January 1997.","official_url":null},{"relationship":"Power off-taker","name":"Southern California Edison Company","detail":"The CEC states that electricity generated by the project is sold to Southern California Edison through a high-voltage transmission connection.","official_url":"https://www.sce.com/"}] — Source · confidence: medium
- Commercial parties: [{"relationship":"Current project owner","name":"Watson Cogeneration Company","detail":"The project owner named in CEC regulatory filings; the entity is consolidated by Marathon Petroleum following MPC’s 2022 purchase of the remaining NRG interest.","official_url":null},{"relationship":"Parent owner / consolidated owner","name":"Marathon Petroleum Corporation","detail":"MPC purchased the remaining 49% interest in Watson Cogeneration from NRG Energy on June 1, 2022, for approximately $59 million.","official_url":"https://www.marathonpetroleum.com/"},{"relationship":"Operator / EIA utility","name":"ARCO Products Co-Watson","detail":"The EIA utility associated with plant ID 50216 and the Watson Cogeneration operating record.","official_url":"https://www.marathonpetroleum.com/Operations/Refining/Los-Angeles-Refinery/"},{"relationship":"Former 49% owner and seller","name":"NRG Energy, Inc.","detail":"NRG held the remaining 49% interest in Watson Cogeneration until selling it to MPC on June 1, 2022. NRG obtained the interest through its acquisition of Edison Mission Energy assets.","official_url":"https://www.nrg.com/"},{"relationship":"Predecessor project owner","name":"ARCO Petroleum Products Company","detail":"The original project owner from which ownership was transferred to Watson Cogeneration Company by CEC approval in June 1988.","official_url":null},{"relationship":"Predecessor portfolio owner / seller to NRG","name":"Edison Mission Energy","detail":"EME was the predecessor portfolio owner whose assets and subsidiary interests, including an interest in Watson Cogeneration, were acquired by NRG.","official_url":null},{"relationship":"Historical co-owner","name":"Products Cogeneration Company","detail":"Held a 51% share before the CEC-approved 1997 transfer of 49% of that share to Carson Cogeneration Company.","official_url":null},{"relationship":"Historical co-owner","name":"Carson Cogeneration Company","detail":"Received the CEC-approved transfer of 49% of the 51% share held by Products Cogeneration Company in January 1997.","official_url":null},{"relationship":"Power off-taker","name":"Southern California Edison Company","detail":"The CEC states that electricity generated by the project is sold to Southern California Edison through a high-voltage transmission connection.","official_url":"https://www.sce.com/"}] — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Commercial parties.0: {"relationship":"Current project owner","name":"Watson Cogeneration Company","detail":"The project owner named in CEC regulatory filings; the entity is consolidated by Marathon Petroleum following MPC’s 2022 purchase of the remaining NRG interest.","official_url":null} — Source · confidence: medium
- Commercial parties.0: {"relationship":"Current project owner","name":"Watson Cogeneration Company","detail":"The project owner named in CEC regulatory filings; the entity is consolidated by Marathon Petroleum following MPC’s 2022 purchase of the remaining NRG interest.","official_url":null} — Source · confidence: medium
- Commercial parties.1: {"relationship":"Parent owner / consolidated owner","name":"Marathon Petroleum Corporation","detail":"MPC purchased the remaining 49% interest in Watson Cogeneration from NRG Energy on June 1, 2022, for approximately $59 million.","official_url":"https://www.marathonpetroleum.com/"} — Source · confidence: high
- Commercial parties.3: {"relationship":"Former 49% owner and seller","name":"NRG Energy, Inc.","detail":"NRG held the remaining 49% interest in Watson Cogeneration until selling it to MPC on June 1, 2022. NRG obtained the interest through its acquisition of Edison Mission Energy assets.","official_url":"https://www.nrg.com/"} — Source · confidence: high
- Commercial parties.4: {"relationship":"Predecessor project owner","name":"ARCO Petroleum Products Company","detail":"The original project owner from which ownership was transferred to Watson Cogeneration Company by CEC approval in June 1988.","official_url":null} — Watson Cogeneration Project | California Energy Commission · confidence: high
- Commercial parties.5: {"relationship":"Predecessor portfolio owner / seller to NRG","name":"Edison Mission Energy","detail":"EME was the predecessor portfolio owner whose assets and subsidiary interests, including an interest in Watson Cogeneration, were acquired by NRG.","official_url":null} — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Commercial parties.6: {"relationship":"Historical co-owner","name":"Products Cogeneration Company","detail":"Held a 51% share before the CEC-approved 1997 transfer of 49% of that share to Carson Cogeneration Company.","official_url":null} — Watson Cogeneration Project | California Energy Commission · confidence: high
- Commercial parties.7: {"relationship":"Historical co-owner","name":"Carson Cogeneration Company","detail":"Received the CEC-approved transfer of 49% of the 51% share held by Products Cogeneration Company in January 1997.","official_url":null} — Watson Cogeneration Project | California Energy Commission · confidence: high
- Commercial parties.8: {"relationship":"Power off-taker","name":"Southern California Edison Company","detail":"The CEC states that electricity generated by the project is sold to Southern California Edison through a high-voltage transmission connection.","official_url":"https://www.sce.com/"} — Source · confidence: high
- Commercial parties.8: {"relationship":"Power off-taker","name":"Southern California Edison Company","detail":"The CEC states that electricity generated by the project is sold to Southern California Edison through a high-voltage transmission connection.","official_url":"https://www.sce.com/"} — Source · confidence: high
- Substation: SCE Hinson Substation — Watson Cogeneration Project | California Energy Commission · confidence: high
- Transmission owner: Southern California Edison (SCE) — Watson Cogeneration Project | California Energy Commission · confidence: medium
- Status detail: Operating: the latest plant record reports 613.5 GWh generated during February–May 2026, and the six EIA generators GN91–GN96 are listed as operating. The 2025 CEC change concerns gas-insulated switchgear construction and a jurisdictional-boundary adjustment, not a stated retirement, fuel conversion, or repowering. — California Energy Commission : Docket Log · confidence: medium

## Timeline

- 1986-09-17 — CEC certification
  The California Energy Commission certified the original Watson Cogeneration Project under docket 85-AFC-01.
  Source: Watson Cogeneration Project | California Energy Commission (https://www.energy.ca.gov/powerplant/combined-cycle/watson-cogeneration-project)
- 1988-04-01 — Commercial operation
  The original project began commercial operation.
  Source: Watson Cogeneration Project | California Energy Commission (https://www.energy.ca.gov/powerplant/combined-cycle/watson-cogeneration-project)
- 1997-10-17 — 45-MW fifth-train approval
  The CEC approved construction of a new 45-MW fifth-train addition.
  Source: Watson Cogeneration Project | California Energy Commission (https://www.energy.ca.gov/powerplant/combined-cycle/watson-cogeneration-project)
- 2012-04-11 — Fifth-train project approval
  The CEC approved Application for Certification 09-AFC-01C for an additional fifth train; the project was later terminated at the owner’s request.
  Source: Watson Cogeneration Project | California Energy Commission (https://www.energy.ca.gov/powerplant/combined-cycle/watson-cogeneration-project)
- 2014-04 — Acquisition closed
  California Energy Commission records upstream ownership change. NRG Energy acquired Edison Mission Energy assets, including interest in Watson Cogeneration. Source does not disclose consideration allocated to Watson.
  Source: Watson Cogeneration Project | California Energy Commission (https://www.energy.ca.gov/powerplant/combined-cycle/watson-cogeneration-project)
- 2015-07-08 — Fifth-train project termination
  The CEC officially terminated the 09-AFC-01C fifth-train project at the owner’s request.
  Source: Watson Cogeneration Project | California Energy Commission (https://www.energy.ca.gov/powerplant/combined-cycle/watson-cogeneration-project)
- 2025-07-03 — CEC amendment petition
  The CEC docketed a Watson Cogeneration petition to amend the project; the filing stated that the proposed changes would not affect compliance and would have no significant environmental impacts.
  Source: Source (https://efiling.energy.ca.gov/GetDocument.aspx?DocumentContentId=101433&tn=264560)

## Sources

- [Los Angeles Refinery | Marathon Petroleum Refineries](https://www.marathonpetroleum.com/Operations/Refining/Los-Angeles-Refinery/) — marathonpetroleum.com · tier other
- [mpc-20220630](https://www.sec.gov/Archives/edgar/data/1510295/000151029522000063/mpc-20220630.htm) — sec.gov · tier regulatory
- [Watson Cogeneration Project | California Energy Commission](https://www.energy.ca.gov/powerplant/combined-cycle/watson-cogeneration-project) — energy.ca.gov · tier regulatory
- [Curtailed and Non-Operational Generator AM Report Apr ...](https://www.caiso.com/documents/curtailed-non-operational-generator-am-report-20160430.html) — caiso.com · tier other
- [Source_Sink_Update](https://www.caiso.com/documents/historical-crr-apnode-name-change-mapping-file.xlsx) — caiso.com · tier other
- [watson cogeneration project (85-afc-01c) petition to amend](https://efiling.energy.ca.gov/GetDocument.aspx?tn=264560&DocumentContentId=101433) — efiling.energy.ca.gov · tier regulatory
- [Energy Service Provider - NAES](https://www.naes.com/) — naes.com · tier other
- [Source](https://energy.ca.gov/powerplant/combined-cycle/watson-cogeneration-project) — energy.ca.gov · tier regulatory
- [7E Gas Turbine (7E.03) | GE Vernova](https://www.gevernova.com/gas-power/products/gas-turbines/7e) — gevernova.com · tier other
- [Source](https://marathonpetroleum.com/Operations/Refining/Los-Angeles-Refinery) — marathonpetroleum.com · tier other
- [Source](https://www.sec.gov/Archives/edgar/data/1510295/000151029523000012/R29.htm) — sec.gov · tier regulatory
- [Source](https://efiling.energy.ca.gov/GetDocument.aspx?DocumentContentId=101433&tn=264560) — efiling.energy.ca.gov · tier regulatory
- [Source](https://www.marathonpetroleum.com/content/documents/Investors/Annual_Report/2024_MPC_Annual_Report_and_10K.pdf) — marathonpetroleum.com · tier other
- [California Energy Commission : Docket Log](https://efiling.energy.ca.gov/Lists/DocketLog.aspx?docketnumber=85-AFC-01C) — efiling.energy.ca.gov · tier regulatory

## Data quality

- The CEC legacy project page reports 385 MW, while current EIA-derived plant records report 405 MW; these figures should not be treated as interchangeable without confirming the reporting boundary or later additions. The 1997 45-MW fifth-train construction approval and the later 2012 fifth-train project are distinct regulatory actions. The 2012 project was terminated in 2015 and should not be counted as an operating expansion. The disclosed $59 million Watson transaction and $2.635 billion NRG–Edison Mission Energy transaction are acquisition consideration, not project-level construction financing. No Watson-specific construction debt or project-financing terms were identified. No retirement or repowering event was identified. A 2025 CEC amendment petition was docketed, but the filing described proposed changes rather than retirement or repowering.

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Canonical page: https://askthegrid.com/assets/facilities/watson-cogeneration

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