# Rosamond South 1

CAISO Solar Photovoltaic, Batteries · https://askthegrid.com/assets/facilities/rosamond-south-1

Rosamond South 1 is a hybrid solar and battery storage facility with 257 MW of EIA-reported total operating capacity and 468 MWh of reported storage energy capacity in Kern County, California, registered as EIA Plant ID 67764. Golden Fields Solar IV, LLC owns and operates the plant, a subsidiary of Clearway Energy Group, LLC. Commercial operation began on November 5, 2025.

## Key facts

- Technology: Solar Photovoltaic, Batteries
- Power capacity: 257 MW
- Energy capacity: 468 MWh
- Operating status: operating

## Grid and market context

- ISO/RTO: CAISO
- Balancing authority: California Independent System Operator (CISO/CAISO)

## Source-backed facts

- Owner logo domain: clearwayenergygroup.com — Golden Fields So · confidence: medium
- Owner logo domain: clearwayenergygroup.com — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: medium
- Identifiers: [{"value":"67764","system":"EIA plant ID"},{"value":"RS1","system":"EIA generator ID"},{"value":"RBESS","system":"EIA generator ID"},{"value":"56988","system":"FERC MBR EIA record ID — RS1"},{"value":"56989","system":"FERC MBR EIA record ID — RBESS"},{"value":"ER20-840-000","system":"FERC docket"},{"value":"Golden Fields Solar IV, LLC — LGIA","system":"CAISO interconnection agreement"},{"value":"CAISO (CISO)","system":"ISO/RTO and balancing authority"}] — Golden Fields So · confidence: medium
- Official project url: https://www.clearwayenergygroup.com/press-releases/clearway-brings-online-grid-enhancing-rosamond-south-energy-center-in-california/ — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Owner name: Golden Fields Solar IV, LLC — Golden Fields So · confidence: high
- Description: Rosamond South 1 is the public project name for EIA plant 67764, registered to Golden Fields Solar IV, LLC, in Kern County, California. It combines a 140 MW solar generator, identified as RS1, with a 117 MW battery generator, identified as RBESS, for 257 MW total capacity. Clearway Energy Group reported that the project reached commercial operations in November 2025. — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Parties: [{"relationship":"Owner and operator / registered utility","name":"Golden Fields Solar IV, LLC","official_url":null},{"relationship":"Parent company","name":"Clearway Energy Group, LLC","official_url":"https://www.clearwayenergygroup.com"},{"relationship":"Engineering, procurement, and construction contractor","name":"McCarthy Building Companies, Inc.","official_url":null},{"relationship":"Construction lender","name":"Societe Generale","official_url":null},{"relationship":"Construction lender","name":"Australia and New Zealand Banking Group Limited","official_url":null},{"relationship":"Construction lender","name":"Siemens Financial Services","official_url":null},{"relationship":"Construction lender","name":"Commerzbank","official_url":null},{"relationship":"Construction lender","name":"CoBank","official_url":null},{"relationship":"Construction lender","name":"DNB Bank ASA","official_url":null},{"relationship":"Construction lender","name":"Nord/LB","official_url":null},{"relationship":"Offtaker","name":"MCE","official_url":null},{"relationship":"Offtaker","name":"The University of California","official_url":null},{"relationship":"Offtaker","name":"Rancho Cucamonga Municipal Utility","official_url":null},{"relationship":"Offtaker","name":"Eastside Power Authority","official_url":null},{"relationship":"Offtaker","name":"City of Moreno Valley","official_url":null},{"relationship":"Offtaker","name":"Constellation Energy","official_url":null}] — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: high
- Parties: [{"relationship":"Owner and operator / registered utility","name":"Golden Fields Solar IV, LLC","official_url":null},{"relationship":"Parent company","name":"Clearway Energy Group, LLC","official_url":"https://www.clearwayenergygroup.com"},{"relationship":"Engineering, procurement, and construction contractor","name":"McCarthy Building Companies, Inc.","official_url":null},{"relationship":"Construction lender","name":"Societe Generale","official_url":null},{"relationship":"Construction lender","name":"Australia and New Zealand Banking Group Limited","official_url":null},{"relationship":"Construction lender","name":"Siemens Financial Services","official_url":null},{"relationship":"Construction lender","name":"Commerzbank","official_url":null},{"relationship":"Construction lender","name":"CoBank","official_url":null},{"relationship":"Construction lender","name":"DNB Bank ASA","official_url":null},{"relationship":"Construction lender","name":"Nord/LB","official_url":null},{"relationship":"Offtaker","name":"MCE","official_url":null},{"relationship":"Offtaker","name":"The University of California","official_url":null},{"relationship":"Offtaker","name":"Rancho Cucamonga Municipal Utility","official_url":null},{"relationship":"Offtaker","name":"Eastside Power Authority","official_url":null},{"relationship":"Offtaker","name":"City of Moreno Valley","official_url":null},{"relationship":"Offtaker","name":"Constellation Energy","official_url":null}] — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Identifiers.5: {"value":"ER20-840-000","system":"FERC docket"} — Golden Fields So · confidence: high
- Parties.1: {"relationship":"Parent company","name":"Clearway Energy Group, LLC","official_url":"https://www.clearwayenergygroup.com"} — Golden Fields So · confidence: high
- Parties.2: {"relationship":"Engineering, procurement, and construction contractor","name":"McCarthy Building Companies, Inc.","official_url":null} — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: high
- Parties.3: {"relationship":"Construction lender","name":"Societe Generale","official_url":null} — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: high
- Parties.4: {"relationship":"Construction lender","name":"Australia and New Zealand Banking Group Limited","official_url":null} — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: high
- Parties.5: {"relationship":"Construction lender","name":"Siemens Financial Services","official_url":null} — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: high
- Parties.6: {"relationship":"Construction lender","name":"Commerzbank","official_url":null} — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: high
- Parties.7: {"relationship":"Construction lender","name":"CoBank","official_url":null} — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: high
- Parties.8: {"relationship":"Construction lender","name":"DNB Bank ASA","official_url":null} — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: high
- Parties.9: {"relationship":"Construction lender","name":"Nord/LB","official_url":null} — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: high
- Parties.10: {"relationship":"Offtaker","name":"MCE","official_url":null} — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Parties.11: {"relationship":"Offtaker","name":"The University of California","official_url":null} — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Parties.12: {"relationship":"Offtaker","name":"Rancho Cucamonga Municipal Utility","official_url":null} — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Parties.13: {"relationship":"Offtaker","name":"Eastside Power Authority","official_url":null} — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Parties.14: {"relationship":"Offtaker","name":"City of Moreno Valley","official_url":null} — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Parties.15: {"relationship":"Offtaker","name":"Constellation Energy","official_url":null} — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Site acres: 1302 — Rosamond South Solar Project by Golden Fields Solar IV, LLC · confidence: medium
- Unit configuration: Two generating units: 140 MW solar photovoltaic generator (RS1) and 117 MW battery energy-storage generator (RBESS), for 257 MW total — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Commercial operation date: 2025-11-05 — Source · confidence: high
- Duration hours: 4 — Rosamond South Solar Project by Golden Fields Solar IV, LLC · confidence: medium
- Product url: https://storage.wartsila.com/technology/gridsolv-quantum/ — Wärtsilä signs contracts to supply energy storage systems for one of the world’s largest solar-plus-storage project portfolios · confidence: medium
- Product url: https://storage.wartsila.com/technology/gridsolv-quantum/ — DeepBlue 4.0 Series - PV Solar products Manufacturer... · confidence: medium
- Manufacturer domain: wartsila.com — Clearway closes $550 million financing for solar-plus-storage project in Kern County – pv magazine USA · confidence: medium
- Equipment models: [{"manufacturer_domain":"jasolar.com","product_url":"https://www.jasolar.com/html/en/","count":null,"unit_mw":null,"name":"JA Solar photovoltaic modules"},{"manufacturer_domain":"nextracker.com","product_url":"https://www.nextracker.com/trackers/","count":null,"unit_mw":null,"name":"Nextracker tracker system"},{"manufacturer_domain":"wartsila.com","product_url":"https://storage.wartsila.com/technology/gridsolv-quantum/","count":null,"unit_mw":null,"name":"Wärtsilä battery energy storage system"}] — Clearway closes $550 million financing for solar-plus-storage project in Kern County – pv magazine USA · confidence: medium
- Manufacturer name: Wärtsilä — Clearway closes $550 million financing for solar-plus-storage project in Kern County – pv magazine USA · confidence: medium
- Equipment models.0: {"manufacturer_domain":"jasolar.com","product_url":"https://www.jasolar.com/html/en/","count":null,"unit_mw":null,"name":"JA Solar photovoltaic modules"} — Clearway closes $550 million financing for solar-plus-storage project in Kern County – pv magazine USA · confidence: medium
- Equipment models.1: {"manufacturer_domain":"nextracker.com","product_url":"https://www.nextracker.com/trackers/","count":null,"unit_mw":null,"name":"Nextracker tracker system"} — Clearway closes $550 million financing for solar-plus-storage project in Kern County – pv magazine USA · confidence: medium
- Equipment models.2: {"manufacturer_domain":"wartsila.com","product_url":"https://storage.wartsila.com/technology/gridsolv-quantum/","count":null,"unit_mw":null,"name":"Wärtsilä battery energy storage system"} — Clearway closes $550 million financing for solar-plus-storage project in Kern County – pv magazine USA · confidence: medium
- Construction scope: Rosamond South 1 is a 140 MW photovoltaic solar facility paired with a 117 MW battery-energy-storage system, forming a 257 MW solar-plus-storage complex. Exact-asset reporting identifies JA Solar PV modules, Nextracker trackers, and a Wärtsilä-provided BESS; McCarthy Building Companies led construction. No installed module, inverter, battery-unit, or container counts were disclosed. — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: medium
- Product url: https://storage.wartsila.com/technology/gridsolv-quantum/ — Source · confidence: medium
- Product url: https://storage.wartsila.com/technology/gridsolv-quantum/ — Wärtsilä Energy Storage - Leading the energy transition · confidence: medium
- Kind: solar — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: high
- Manufacturer domain: wartsila.com — Source · confidence: medium
- Manufacturer name: Wärtsilä — Source · confidence: medium
- Equipment models.2: {"manufacturer_domain":"wartsila.com","product_url":"https://storage.wartsila.com/technology/gridsolv-quantum/","count":null,"unit_mw":null,"name":"Wärtsilä battery energy storage system"} — Source · confidence: medium
- Significance: Rosamond South 1 is a 257 MW solar-plus-storage complex comprising a 140 MW photovoltaic generator and a 117 MW battery system. Clearway says the facility can power more than 72,000 homes annually and deploy energy during peak demand. — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: medium
- Description: Rosamond South 1 is located in Kern County, California, and combines the 140 MW RS1 photovoltaic generator with the 117 MW RBESS battery generator. The facility is registered to Golden Fields Solar IV, LLC and is associated with Clearway Energy Group. Construction began in August 2024 after the project secured construction financing, and the complex reached commercial operations on November 5, 2025. Its long-term offtakers include MCE, the University of California, Rancho Cucamonga Municipal Utility, Eastside Power Authority, the City of Moreno Valley, and Constellation Energy. — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: medium
- Description: Rosamond South 1 is located in Kern County, California, and combines the 140 MW RS1 photovoltaic generator with the 117 MW RBESS battery generator. The facility is registered to Golden Fields Solar IV, LLC and is associated with Clearway Energy Group. Construction began in August 2024 after the project secured construction financing, and the complex reached commercial operations on November 5, 2025. Its long-term offtakers include MCE, the University of California, Rancho Cucamonga Municipal Utility, Eastside Power Authority, the City of Moreno Valley, and Constellation Energy. — Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy · confidence: medium
- Quality notes: ["The reported 257 MW combined capacity is the sum of the separately reported 140 MW solar and 117 MW storage ratings; The documented milestones are regulatory filings, construction financing and start, and commercial operation."] — Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy · confidence: medium
- Quality notes: ["The reported 257 MW combined capacity is the sum of the separately reported 140 MW solar and 117 MW storage ratings; The documented milestones are regulatory filings, construction financing and start, and commercial operation."] — Federal Register :: Golden Fields Solar IV, LLC; Supplemental Notice That Section 205 Rate Filing Includes Request for Blanket Section 204 Authorization · confidence: medium

## Timeline

- 2024-08-26 — Construction financing and construction start
  Clearway Energy Group announced $550 million of construction financing and the start of construction on the Rosamond South I solar-and-storage project.
  Source: Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy (https://www.clearwayenergygroup.com/press-releases/clearway-closes-financing-and-starts-construction-on-solar-and-energy-storage-project-in-california/)
- 2025-11-05 — Commercial operation
  Clearway announced that Rosamond South 1 had reached commercial operations as a 140 MW solar and 117 MW energy-storage complex.
  Source: Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy (https://www.clearwayenergygroup.com/press-releases/clearway-brings-online-grid-enhancing-rosamond-south-energy-center-in-california/)

## Sources

- [Golden Fields So](https://www.ferc.gov/sites/default/files/2020-06/20200317153707-ER20-840-000.pdf) — ferc.gov · tier regulatory
- [Clearway Brings Online Grid-Enhancing Rosamond South Energy Center in California - Clearway Energy](https://www.clearwayenergygroup.com/press-releases/clearway-brings-online-grid-enhancing-rosamond-south-energy-center-in-california/) — clearwayenergygroup.com · tier other
- [Clearway Closes Financing and Starts Construction on Solar and Energy Storage Project in California - Clearway Energy](https://www.clearwayenergygroup.com/press-releases/clearway-closes-financing-and-starts-construction-on-solar-and-energy-storage-project-in-california/) — clearwayenergygroup.com · tier other
- [Source](https://movalarchive.org/archive/2023/Attachments/Attachment-15051.pdf) — movalarchive.org · tier other
- [Rosamond South Solar Project by Golden Fields Solar IV, LLC](https://ceqanet.lci.ca.gov/2021060079/3) — ceqanet.lci.ca.gov · tier regulatory
- [Source](https://clearwayenergygroup.com/press-releases/clearway-brings-online-grid-enhancing-rosamond-south-energy-center-in-california) — clearwayenergygroup.com · tier other
- [Clearway closes $550 million financing for solar-plus-storage project in Kern County – pv magazine USA](https://pv-magazine-usa.com/2024/08/27/clearway-closes-550-million-financing-for-solar-plus-storage-project-in-kern-county/) — pv-magazine-usa.com · tier other
- [Wärtsilä signs contracts to supply energy storage systems for one of the world’s largest solar-plus-storage project portfolios](https://www.wartsila.com/media/news/11-07-2022-wartsila-signs-contracts-to-supply-energy-storage-systems-for-one-of-the-world-s-largest-solar-plus-storage-project-portfolios-3130241) — wartsila.com · tier other
- [DeepBlue 4.0 Series - PV Solar products Manufacturer ...](https://www.jasolar.com/index.php?m=content&c=index&a=lists&catid=453) — jasolar.com · tier other
- [Source](https://wartsila.com/media/news/11-07-2022-wartsila-signs-contracts-to-supply-energy-storage-systems-for-one-of-the-world-s-largest-solar-plus-storage-project-portfolios-3130241) — wartsila.com · tier other
- [Wärtsilä Energy Storage - Leading the energy transition](https://storage.wartsila.com/technology/gridsolv-quantum/) — storage.wartsila.com · tier other
- [Federal Register :: Golden Fields Solar IV, LLC; Supplemental Notice That Section 205 Rate Filing Includes Request for Blanket Section 204 Authorization](https://www.federalregister.gov/documents/2020/02/27/2020-03923/golden-fields-solar-iv-llc-supplemental-notice-that-section-205-rate-filing-includes-request-for) — federalregister.gov · tier regulatory
- [Clearway wraps up 140-MW solar, 117-MW storage project ...](https://www.solarpowerworldonline.com/2025/11/clearway-wraps-up-140-mw-solar-117-mw-storage-project-in-kern-county/) — solarpowerworldonline.com · tier other
- [McCarthy Building Companies - Reliable Construction](https://www.mccarthy.com/) — mccarthy.com · tier other
- [Home - Societe Generale Group](https://www.societegenerale.com/en) — societegenerale.com · tier other
- [ANZ United States of America](https://www.anz.com/institutional/global/united-states-of-america/en/) — anz.com · tier other
- [Siemens Financial Services](https://www.siemens.com/en-us/company/about/businesses/financial-services/) — siemens.com · tier other
- [Home Commerzbank Group - Group Website](https://www.commerzbank.de/group/) — commerzbank.de · tier other
- [CoBank: Financing solutions for rural communities and ...](https://www.cobank.com/) — cobank.com · tier other
- [DNB - Bank from A to Z](https://www.dnb.no/en) — dnb.no · tier other
- [NORD/LB - Creating true value.: NORD/LB](https://www.nordlb.com/) — nordlb.com · tier other
- [MCE Community Choice Energy](https://mcecleanenergy.org/) — mcecleanenergy.org · tier other
- [University of California: Home](https://www.universityofcalifornia.edu/) — universityofcalifornia.edu · tier other
- [Welcome to RCMU | City of Rancho ...](https://www.cityofrc.us/rcmu) — cityofrc.us · tier other
- [Eastside Power Authority – Powering Agriculture For The Future](https://eastsidepa.org/) — eastsidepa.org · tier other
- [City of Moreno Valley, California](https://www.moreno-valley.ca.us/) — moreno-valley.ca.us · tier other
- [Constellation Energy: Powering America's Clean and Reliable ...](https://www.constellationenergy.com/) — constellationenergy.com · tier other
- [Announced Resource Retirement and Mothball List posted | California ISO](https://www.caiso.com/notices/announced-resource-retirement-and-mothball-list-posted-4) — caiso.com · tier other
- [F O R M 1 0 - K](https://www.sec.gov/Archives/edgar/data/1567683/000110465926034006/tm268772d2_ars.pdf) — sec.gov · tier regulatory
- [Our Projects & Customers - Clearway Energy](https://www.clearwayenergygroup.com/esg/2025-sustainability-report/business-sustainability-hub/our-projects/) — clearwayenergygroup.com · tier other

## Data quality

- The reported 257 MW combined capacity is the sum of the separately reported 140 MW solar and 117 MW storage ratings; The disclosed $550 million amount is construction financing for the project and is not disclosed as sale consideration or a portfolio purchase price. No publicly disclosed acquisition, sale, predecessor-owner, expansion, retirement, or repowering event was identified for this exact project. The documented milestones are regulatory filings, construction financing and start, and commercial operation.

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