Summary of the hydro share series

What this dataset measures

Tests two common claims: that hydropower supplies most of Washington's electricity, and that Grand Coulee is the largest U.S. power plant. Both depend on the measure used (in-state generation versus delivered power; capacity versus annual output), so the release keeps each measure separate.

Geography

Washington State, United States

Unit of observation

Mostly one state-year; plant tables are one EIA plant in 2025.

Update cadence

Immutable research release; EIA annual data for 2026 would be published as a new version.

Curator

FactHub Research Team

Supporting files

Source snapshots, manifests, quality reports, documentation, and other materials used to produce or review this release.

• dataset-parts.json Documentation · application/json · 71.3 KB (73,000 bytes)

  Sources, tables, events, saved analyses and replications of this dataset version, as JSON.

• source-manifest.json Source manifest · application/json · 2 KB (2,088 bytes)

  URL, byte length and SHA-256 of every downloaded source file.

• README.md Documentation · text/markdown · 2.1 KB (2,149 bytes)

  Contents, definitions and reproduction steps.

• quality-report.md Quality report · text/markdown · 1.3 KB (1,311 bytes)

  Cross-checks and data-quality notes.

• build.js Transformation manifest · text/javascript · 15.1 KB (15,416 bytes)

  Reads the EIA and Commerce source files and writes every table (Node.js 20 + SheetJS).

• build_payload.js Transformation manifest · text/javascript · 40.7 KB (41,716 bytes)

  Writes the release files and this dataset's FactHub content.

Saved analyses

Sources

1. U.S. Energy Information Administration, State Historical Tables: Net Generation by State by Type of Producer by Energy Source, 1990-2025 (Final, released September 2026) Primary source for annual Washington net generation by energy source and for the state hydro ranking (EIA-923 and predecessor forms).

   Retrieved October 9, 2026. U.S. federal government work (public domain). Linked as a public record; the source file is not redistributed. Its SHA-256 is recorded here and in source-manifest.json.

   Archived copy captured October 9, 2026

2. U.S. Energy Information Administration, State Electricity Profile tables for Washington (data year 2024) Table 10 (supply and disposition: retail sales, international trade, net interstate trade) and cross-check of Table 5 generation totals.

   Retrieved October 9, 2026. U.S. federal government work (public domain). Linked as a public record; the source file is not redistributed. Its SHA-256 is recorded here and in source-manifest.json.

   Archived copy captured October 9, 2026

3. U.S. Energy Information Administration, Form EIA-860 Annual Electric Generator Report, 2025 final data (eia8602025.zip, file 3_1_Generator_Y2025.xlsx, sheet Operable) Generator-level nameplate, summer and winter capacity used to rank U.S. plants by capacity.

   Retrieved October 9, 2026. U.S. federal government work (public domain). Linked as a public record; the source file is not redistributed. Its SHA-256 is recorded here and in source-manifest.json.

   Archived copy captured October 9, 2026

4. U.S. Energy Information Administration, Form EIA-923 Power Plant Operations Report, 2025 final data (f923_2025.zip, Schedules 2-5, Page 1 Generation and Fuel Data) Plant-level 2025 net generation used to rank U.S. plants by annual output.

   Retrieved October 9, 2026. U.S. federal government work (public domain). Linked as a public record; the source file is not redistributed. Its SHA-256 is recorded here and in source-manifest.json.

   Archived copy captured October 9, 2026

5. Washington State Department of Commerce, Fuel Mix Disclosure Consumption-side check: the aggregate 2024 fuel mix of electricity Washington utilities reported delivering to Washington customers.

   Retrieved October 9, 2026. Washington State public record. Linked as a public record; the source file is not redistributed. Its SHA-256 is recorded here and in source-manifest.json.

   Archived copy captured October 9, 2026

6. Washington State Department of Commerce, chart "Washington electric utilities aggregate 2024 fuel mix" (image on the Fuel Mix Disclosure page) The labeled percentages transcribed into the wa-utility-fuel-mix-2024 table.

   Retrieved October 9, 2026. Washington State public record. Linked as a public record; the source file is not redistributed. Its SHA-256 is recorded here and in source-manifest.json.

7. U.S. Bureau of Reclamation, Grand Coulee Dam: About Operator statement of Grand Coulee generating capacity (6,809 MW) and typical output (up to 21 billion kWh), used as a replication check.

   Retrieved October 9, 2026. U.S. federal government work (public domain). Linked as a public record; the source file is not redistributed. Its SHA-256 is recorded here and in source-manifest.json.

   Archived copy captured October 9, 2026

8. U.S. Energy Information Administration, Today in Energy, "Drought conditions reduce hydropower generation, particularly in the Pacific Northwest" (November 7, 2024) Context on 2023-2024 Pacific Northwest hydro conditions; states Grand Coulee net summer capacity as 6.7 GW.

   Retrieved October 9, 2026. U.S. federal government work (public domain). Linked as a public record; the source file is not redistributed. Its SHA-256 is recorded here and in source-manifest.json.

   Archived copy captured October 9, 2026

9. Washington State Department of Ecology, news release, April 16, 2024 drought declaration Dates the 2024 statewide drought emergency and the 2023 emergency covering 12 watersheds.

   Retrieved October 9, 2026. Washington State public record. Linked as a public record; the source file is not redistributed. Its SHA-256 is recorded here and in source-manifest.json.

   Archived copy captured October 9, 2026

Limitations and reproducibility

Fully reproducible from public downloads with Node.js 20 and SheetJS.: source-manifest.json lists every downloaded file with URL and SHA-256; build.js regenerates every table from those files and build_payload.js regenerates the release. The Commerce fuel-mix percentages are transcribed from a chart and are typed into build.js.

• Net generation measures electricity produced by plants located in Washington, not the electricity Washington customers use; Washington trades large volumes with other states and Canada.
• Conventional hydro excludes pumped storage, which EIA reports separately and which is near zero or negative in Washington.
• Washington's hydro output depends on Columbia River Basin water supply, so any single year can differ from the long-run pattern; 2023 and 2024 were drought years.
• Plant rankings use EIA plant codes and 2025 data only; capacity rankings use year-end operable generators.
• The consumption-side fuel mix covers 2024 only and includes 15.44% unspecified power.