Marathon Bay Area Cogen
Marathon Bay Area Cogen is a 114 MW natural gas power plant in Contra Costa County, California, operated by Tesoro Marketing & Refining Co. LLC (Martinez). EIA-860M lists 3 generating units here, inside CAISO. Its units entered service in 1987.
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
- 113.5 MW
- 103.5 MW net summer
- Generating units
- 3
- In service
- 1987
- EIA plant ID
- 10342
Where it is
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- County
- Contra Costa County, California
- Coordinates
- 38.0244, -122.0589
- Balancing authority
- CISO
- Sector
- IPP CHP
Units, technology and status
- Operator of record
- Tesoro Marketing & Refining Co. LLC (Martinez)
- Primary energy source
- Natural gas
- Technologies
- Natural Gas Fired Combined Cycle
- Status
- Operating
Every plant Tesoro Marketing & Refining Co. LLC (Martinez) reports to EIA →
Marathon Bay Area Cogen: FAQ
- Where is Marathon Bay Area Cogen?
- In Contra Costa County, California (CA). 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 Marathon Bay Area Cogen?
- 114 MW of nameplate capacity across 3 units, as of the EIA-860M release for 2026-07.
- Who owns Marathon Bay Area Cogen?
- EIA-860M names Tesoro Marketing & Refining Co. LLC (Martinez) 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 Marathon Bay Area Cogen LLC?
- Probably, but EIA-860M does not say. The survey records a plant name and a reporting entity — Tesoro Marketing & Refining Co. LLC (Martinez) 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 "Marathon Bay Area Cogen LLC" usually means this site. This page shows only what EIA files, and does not assert a corporate structure it cannot see.
- Is Marathon Bay Area Cogen still running?
- EIA-860M files it as "Operating" for 2026-07. Statuses change monthly, and this page follows the monthly release.