How big is Mariposa Energy Project?

Mariposa Energy Project has a reported capacity of 199.6 MW. Source: EIA Form 860.

What kind of plant is Mariposa Energy Project?

Mariposa Energy Project is a Natural Gas Fired Combustion Turbine facility in Alameda County, CA, participating in the CAISO market.

Where is Mariposa Energy Project located?

Mariposa Energy Project is in Alameda County, CA, inside the CAISO balancing area.

Who operates Mariposa Energy Project?

Mariposa Energy Project is operated by Diamond Generating Corporation according to the EIA generator inventory. Reporting membership does not by itself establish ultimate ownership.

How much electricity does Mariposa Energy Project generate?

Mariposa Energy Project reported 22.8 GWh over the twelve months to 2026-06. Figures are net generation as filed to EIA-923.

Where does Mariposa Energy Project connect to the grid?

Mariposa Energy Project interconnects at Kelso Substation, on the Pacific Gas and Electric Company (PG&E) system.

How does Mariposa Energy Project compare to other plants?

By capacity, Mariposa Energy Project ranks #246 of 825 operating plants of the same technology nationally. It ranks #15 of 136 in CA.

Mariposa Energy Project — 200 MW gas plant, CA

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Mariposa Energy Project — 200 MW gas plant, CA · Ask the Grid

Overview

Reported capacity: 199.6 MW
EIA-reported plant capacity; other capacity bases are withheld pending reconciliation.
Technology: Natural Gas Fired Combustion Turbine
Primary generation technology.
Registry anchor: Plant 57483
Diamond Generating Corporation · Alameda County · CAISO
Operating status: Operating
Mariposa Energy Project is operating.
Grid connection: Kelso Substation
230 kV · Pacific Gas and Electric Company (PG&E)
Commercial operation: October 2011
Best-supported operating milestone.

Profile

Grid role: Dispatchable peaking and grid-stability support, with 10-minute startup capability.
Grid connection: Kelso Substation · 230 kV · Pacific Gas and Electric Company (PG&E).
Physical build: Approximately 200 MW natural-gas-fired simple-cycle generating facility consisting of four General Electric LM6000 PC-SPRINT combustion turbine generators and associated equipment, with dry cooling, zero-liquid-discharge systems, a 580-foot natural-gas pipeline, and a 1.8-mile water connection.

Structured profile

Reported capacity: 199.6 MW
Natural Gas Fired Combustion Turbine
Commercial operation: October 2011
Operating status: operating
Mariposa Energy Project is operating.
Interconnection: Kelso Substation
230 kV · Pacific Gas and Electric Company (PG&E)
Location: Alameda County
CAISO

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Units and generators

Operating generator records and technology attributes reported through EIA-860.

Generator	Capacity	Technology	Operation	Status
CTG1	49.9 MW 49.9 MW summer	Natural Gas Fired Combustion Turbine Natural Gas · GT	Oct 2012	Operating
CTG2	49.9 MW 49.9 MW summer	Natural Gas Fired Combustion Turbine Natural Gas · GT	Oct 2012	Operating
CTG3	49.9 MW 49.9 MW summer	Natural Gas Fired Combustion Turbine Natural Gas · GT	Oct 2012	Operating
CTG4	49.9 MW 49.9 MW summer	Natural Gas Fired Combustion Turbine Natural Gas · GT	Oct 2012	Operating

Performance

Monthly EIA generation history and recent market-resource behavior where linked telemetry is available.

Peer context

Technology capacity: 199.6 MW; Natural Gas Fired Combustion Turbine
National rank: #246; of 825 operating peers
CA rank: #15; of 136 operating peers

Monthly generation

Download CSV

Latest 12 months

22.8 GWh

Reported net generation

Latest report

Jun 2026

EIA-923 monthly filing

2025 capacity factor

1.7%

Using current reported nameplate capacity

Grid and market context

Deterministic links to ERCOT market resources, price records, outage disclosures, queue records, and nearby infrastructure. Candidate joins remain labeled until corroborated.

Nearby substations

HIFLD infrastructure inventory

KELSO

IN SERVICE · 230 kV

0.9 km

TAP302581

Commercial, land, and environmental record

Source-backed project transactions, agreements, land records, permits, and environmental disclosures. Portfolio and adjacent-project facts remain explicitly scoped.

Transactions and agreements

Offtake Agreement Approval

Oct 15, 2009

The California Public Utilities Commission approved PG&E's 10-year fuel-conversion PPA with Mariposa Energy, LLC for dispatchable energy and capacity from the Mariposa Energy Project's four combustion turbines. The agreement is structured as a tolling agreement: PG&E purchases and supplies natural gas and schedules facility power. Contracted output is 184 MW under peak-July conditions, with anticipated initial delivery on July 1, 2012, delivered to PG&E's Kelso 230-kV substation.

184 MW contracted10 yearsPacific Gas and Electric Company · Mariposa Energy, LLC

Source

Land and environmental record

Agricultural Land-Use Restriction

1989

Agricultural Preserve No. 1971-34; Land Conservation Agreement C-89-1195

The parcel historically supported non-irrigated grazing on nonprime agricultural land. The CEC record states that Alameda County entered Land Conservation Agreement No. C-89-1195 with Steven Shin-Der Lee and allowed the power-generation/wastewater-distillation use as a compatible use.

DOCKET

Air-Quality Permit Identifiers

BAAQMD Application 20737; Plant No. 19730; Title V permit B9730

The Bay Area Air Quality Management District issued the Final Determination of Compliance for the project under Application 20737. Later regulatory references identify Plant No. 19730, and the BAAQMD Title V directory lists Mariposa Energy LLC under permit B9730.

Final Determination of Compliance Mariposa Energy Project

Ancillary Construction Acreage

2009

5-acre construction laydown/worker parking area; 1-acre BBID pipeline laydown area; 0.6-acre transmission-line laydown area

The AFC record identifies these temporary or ancillary construction areas adjacent to the project, at the Byron Bethany Irrigation District headquarters, and along the route to the PG&E Kelso Substation. This scoped fact refers to construction and ancillary areas, not the operating facility footprint.

DOCKET

Cooling And Wastewater Management

Dry cooling and zero liquid discharge

The owner/operator project page describes Mariposa as using a dry-cooling system and operating as a zero-liquid-discharge site. CEC water-resource materials also describe a proposed ZLD system for wastewater management.

Mariposa Energy Project | DGLLC

Landowner And Lease

2009

Steven Shin-Der Lee; leased by Diamond Generating Corporation

CEC project records identify Steven Shin-Der Lee as the owner of the 158-acre parcel and state that Diamond Generating Corporation, the parent of Mariposa Energy LLC, leased the parcel. The lease statement is historical project-record information and is not treated as a current title determination.

DOCKET

Related parties and identifiers

Parties, market resources, and identifiers tied to this asset, with owner, operator, developer, EPC, compliance provider, and interconnecting entity roles kept separate.

Relationship graph

Drag organizations to explore the network. Select a node to pin its details and available page link.

AssetOwner / operatorContractorOfftaker

Timeline and sources

Project milestones and public references behind the asset profile.

Project timeline

Jun 15, 2009
Jun 15, 2009
Application For CertificationSource
Mariposa Energy LLC filed an Application for Certification with the California Energy Commission to construct and operate the natural-gas-fired simple-cycle peaking facility.
Nov 2010
Nov 2010
Permitting and original ownership structure

Reporting portfolio

EIA reporting entity

Diamond Generating Corporation

Entity 49981

Operating portfolio

3 plants

1 states

Reported capacity

449.1 MW

Natural Gas Fired Combustion Turbine

Largest reported plants in this portfolio
Largest reported plants	Capacity	State
Mariposa Energy ProjectCurrent	199.6 MW	CA
Indigo Energy Facility	149.7 MW	CA
Larkspur Energy Facility	99.8 MW	CA

Portfolio membership follows the latest EIA-860 reporting entity. It does not imply ultimate ownership.

View full reporting portfolio

Mariposa Energy Project

Mariposa Energy Project

Overview

Profile

Structured profile

Related assets

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Richmond Cogen

Units and generators

Performance

Peer context

Monthly generation

Grid and market context

Nearby substations

Commercial, land, and environmental record

Transactions and agreements

Land and environmental record

Related parties and identifiers

Relationship graph

Timeline and sources

Project timeline

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Parties and identifiers

Reporting portfolio

Sources

Common questions about Mariposa Energy Project

How big is Mariposa Energy Project?

What kind of plant is Mariposa Energy Project?

Where is Mariposa Energy Project located?

Who operates Mariposa Energy Project?

How much electricity does Mariposa Energy Project generate?

Where does Mariposa Energy Project connect to the grid?

How does Mariposa Energy Project compare to other plants?

Co-located assets