How big is Dion R Holm?

Dion R Holm has a reported capacity of 180.2 MW. Source: EIA Form 860.

What kind of plant is Dion R Holm?

Dion R Holm is a Conventional Hydroelectric facility in Tuolumne County, CA, participating in the CAISO market.

Where is Dion R Holm located?

Dion R Holm is in Tuolumne County, CA, inside the CAISO balancing area.

Who operates Dion R Holm?

Dion R Holm is operated by City & County of San Francisco according to the EIA generator inventory. Reporting membership does not by itself establish ultimate ownership.

How much electricity does Dion R Holm generate?

Dion R Holm reported 592.5 GWh over the twelve months to 2026-04. Figures are net generation as filed to EIA-923.

Where does Dion R Holm connect to the grid?

Dion R Holm on the City & County of San Francisco system.

How does Dion R Holm compare to other plants?

By capacity, Dion R Holm ranks #77 of 1,349 operating plants of the same technology nationally. It ranks #10 of 210 in CA.

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Conventional HydroelectricCAISO · Tuolumne County

Dion R Holm

Mitchell Engineering · Tuolumne County · CAISO

Dion R Holm is a hydroelectric facility with 180.2 MW of EIA-reported operating capacity in Tuolumne County, California, registered as EIA Plant ID 380. City & County of San Francisco is the registered plant entity or operator. Holm is the largest of the three hydroelectric powerhouses in San Francisco’s Hetch Hetchy Power System. Its two vertical-shaft, turbine-driven generators are each rated at 82,500 kVA.

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plant:plant-380

Ask about Dion R Holm

Investigate technology, capacity, output, price behavior, ownership, and related facilities using this profile plus current grid data.

Overview

Key fields

Reported capacity: 180.2 MW
EIA-reported operating capacity; nameplate, seasonal, AC/DC, and unit ratings may differ.
Technology: Conventional Hydroelectric
Primary generation technology.
Registry anchor: Plant 380
City & County of San Francisco · Tuolumne County · CAISO
Operating status: Operating
Dion R Holm is operating.

Profile

Grid role: Bulk hydroelectric generation within SFPUC’s Hetch Hetchy Power System, with output transmitted at bulk voltage for resale, wheeling, and municipal loads.
Context: Dion R. Holm is the largest of the three hydroelectric powerhouses in San Francisco’s Hetch Hetchy Power System. Its two vertical-shaft, turbine-driven generators are each rated at 82,500 kVA.
Physical build: Built in 1960, the Dion R. Holm Powerhouse is fed by a six-mile pressure tunnel from Cherry Dam and contains two vertical-shaft, turbine-driven generators rated at 82,500 kVA each. The documented Holm Unit 2 rehabilitation includes 13.8-kV equipment upgrades, addition and integration of a generator breaker, replacement of two 13.8-kV feed breakers and the Unit 2 main control board, plus integration of exciter, governor, and Generator 2 PLCs into the existing SCADA system.

Structured profile

Reported capacity: 180.2 MW
Conventional Hydroelectric
Operating status: operating
Dion R Holm is operating.
Location: Tuolumne County
CAISO
Operator: City & County of San Francisco
Asset role

Units and generators

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

Generator	Capacity	Technology	Operation	Status
1	90.1 MW 90.1 MW summer	Conventional Hydroelectric Water · HY	Aug 1960	Operating
2	90.1 MW 90.1 MW summer	Conventional Hydroelectric Water · HY	Aug 1960	Operating

Performance

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

Peer context

Technology capacity: 180.2 MW
National rank: #77
CA rank: #10

Monthly generation

Download CSV

Latest 12 months

592.5 GWh

Reported net generation

Latest report

Apr 2026

EIA-923 monthly filing

2025 capacity factor

36.6%

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

EARLY INTAKE

IN SERVICE · 115 kV

2.4 km

MI-WUK

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

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AssetOwner / operatorContractor

Parties and identifiers

OrganizationRoleBasis

Timeline and sources

Project milestones and public references behind the asset profile.

Project timeline

Aug 1960
Aug 1960
Generators enter operationEIA-860
EIA-860 lists generator 1, generator 2 with this operating date.
Aug 1, 1960
Aug 1, 1960
Commercial Operation Began

Reporting portfolio

EIA reporting entity

City & County of San Francisco

Entity 16612

Operating portfolio

5 plants

1 states

Reported capacity

421.6 MW

Conventional Hydroelectric · Other Waste Biomass

Largest reported plants in this portfolio
Largest reported plants	Capacity	State
Dion R HolmCurrent	180.2 MW	CA
R C Kirkwood	132.8 MW	CA
Moccasin	103.6 MW	CA
Moccasin Low Head Hydro Project	2.9 MW	CA
SF Southeast Cogen Plant	2.1 MW	CA

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

View full reporting portfolio

Dion R Holm

Ask about Dion R Holm

Dion R Holm

Ask about Dion R Holm

Overview

Key fields

Profile

Structured profile

Units and generators

Performance

Peer context

Monthly generation

Grid and market context

Nearby substations

Related parties and identifiers

Relationship graph

Parties and identifiers

Timeline and sources

Project timeline

Reporting portfolio

Sources

Common questions about Dion R Holm

How big is Dion R Holm?

What kind of plant is Dion R Holm?

Where is Dion R Holm located?

Who operates Dion R Holm?

How much electricity does Dion R Holm generate?

Where does Dion R Holm connect to the grid?

How does Dion R Holm compare to other plants?

Co-located assets

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