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162 MW Hydro operating in Lewis, WA
162 MW
Nameplate Capacity
4
Generators
units
Conventional Hydroelectric
Technology
1963
Operating Since
Coordinates
46.5035, -122.5885
County
Lewis, WA
Nearby Plants
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Owner data does not fully agree across sources.
EIA typically reports the operating utility, while GEM resolves to the financial owner or parent corporation. Both can be correct.
| Field | EIA | GEM | Wikidata |
|---|---|---|---|
| Operator | City of Tacoma - (WA) | Tacoma Power | — |
| Owner(s) | City of Tacoma - (WA) | Tacoma Power | — |
| Status | Operating | operating | — |
GEM identifies the owner as Tacoma Power
This entity is not yet in the GEM ownership database — chain unavailable.
The Mayfield hydroelectric plant, located in Lewis County, Washington, has a total capacity of 162 MW across four generators. The plant began operating in 1963 and is owned and operated by the City of Tacoma. It utilizes conventional hydroelectric technology with water as its primary fuel source (WAT). Mayfield is ranked as the 18th largest power plant in Washington state out of 23, and 120th nationally out of 194.
In the most recent year with available data, Mayfield generated 576,354 MWh of electricity, resulting in a capacity factor of 40.6%. The plant operates within the Western Electricity Coordinating Council (WECC) NERC region, and the balancing authority is the City of Tacoma, Department of Public Utilities, Light Division.
Generated from EIA, GEM, and public data sources
Grid Region
Pacific Northwest
Market
WEIM Participant
NERC Region
WECC — Western Electricity Coordinating Council
Balancing Authority
City of Tacoma, Department of Public Utilities, Light Division (TPWR)
Grid Voltage
240.0 kV
Regulatory Status
RE — Regulated
Entity Type
Municipal
Sector
Electric Utility
Monthly net generation as reported to EIA-923 — useful for historical context. Confidence varies sharply by fuel type; the band above and the “About this data” button explain the caveats specific to this plant and how InfraSure’s in-house model handles them.
56.9K MWh
Latest Month
576.4K MWh
Annual Generation
40.6%
Capacity Factor
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2013
$2,294/kW
Est. Construction Cost
Total estimated cost: $371.7M
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This plant's balancing authority participates in CAISO's Western Energy Imbalance Market (WEIM). Direct nodal pricing data is not yet available.
No wholesale contracts disclosed in FERC EQR for this plant.
FERC EQR captures bilateral wholesale energy + capacity contracts ≥$1M/yr filed quarterly by jurisdictional sellers — covers renewable PPAs, thermal energy sales agreements, capacity contracts, and tolling agreements alike. Many plants don't appear: regulated-utility output flows to ratepayers via cost-of-service rather than bilateral contracts; small projects fall below the filing threshold; tax-equity-financed renewables route offtake to investors not utilities; merchant plants sell into ISO clearing markets without bilateral contracts. News-extracted buyer facts (below) may surface contracts disclosed only through announcements.
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