Wailuku River Hydroelectric — United States of America

Wailuku River Hydroelectric is a 10.4 MW hydro power plant in Hawaii, United States of America. It is operated by Wailuku Holding Company LLC. Based on reported annual generation of 24 GWh, it can supply roughly 6.9k homes. It ranks #5574 of 10,884 United States of America power plants by installed capacity. Commissioned in 1993, it is around 33 years old — long-established. As a non-combustion source, it has no direct CO₂ emissions from generation. In context, hydro supplies about 5.3% of United States of America's electricity; the national grid averages 384 gCO₂/kWh (43.0% low-carbon) (2025).

Plant data: WRI Global Power Plant Database (CC BY 4.0), id USA0054827.

Data provenance

Source of the capacity and fuel values:

capacity: Wikidata P2109; fuel: WRI GPPD

In context: how this plant compares

At 10.4 MW, Wailuku River Hydroelectric is well above the median hydro plant in United States of America (8 MW). Hydropower converts the energy of falling or flowing water into electricity; output depends on rainfall and reservoir level, and large dams also provide grid balancing and storage.

Capacity comparison computed from the WRI Global Power Plant Database; fuel-type context is general engineering background.

Key facts

Load factor

26%, from 24 GWh of reported generation; the median for 1342 hydro plants in United States of America that report generation is 42%

Generation trend

15 GWh in 2013 and 24 GWh in 2019 (+59%)

Highest and lowest year

2018: 42 GWh; 2013: 15 GWh

Share of United States of America hydro capacity

less than 0.1% of 102,513 MW across 1,449 plants in this dataset

Age among peers

1,306 of 1,444 dated hydro plants in United States of America are older

Calculated from the capacity and generation records in this dataset (WRI Global Power Plant Database (CC BY 4.0)).

Reported generation trend

Annual generation (GWh), WRI Global Power Plant Database (CC BY 4.0).

Owner

Operated by Wailuku Holding Company LLC.

Local climate & thermal context

This hydro plant converts the energy of falling or flowing water through hydro turbines. It sits in a temperate oceanic climate (Köppen Cfb) — Northern Hemisphere, latitude 19.7°N — which shapes how much energy it can produce and how its output varies through the year.

Monthly mean temperature

This site has effectively no heating season (tropical/equatorial climate), so winter heat loss is not the driver here. The thermal concern shifts to year-round process heat and humidity/heat-driven corrosion of hot equipment.

Climate normals: WorldClim 2.1 (1970–2000 monthly normals, 10 arc-min, CC BY 4.0); zone: Köppen-Geiger world climate classification (Kottek et al. 2006, 0.5° grid). Degree-days & heat-demand index computed by PowerAtlas — a modelled heat-demand proxy, not a measured site figure.

Site climate & environmental severity

This site sits in an aggressive, high-corrosion environment (estimated ISO 9223 class C5 — Very high), with marine salt corrosion the leading environmental stress.

Indicative estimate via the ISO 9223:2012 informative method (atmospheric corrosivity from temperature, time-of-wetness and airborne salinity), using WorldClim climate normals, the Köppen-Geiger class and coast distance. Indicative, not a measured corrosion rate.

How it compares & nearby plants

The #634 largest hydro power plant of 1449 in United States of America by capacity.

United States of America has 1449 hydro power plants in this dataset, together about 102,513 MW of capacity.

Nearby power plants

• Waiau Hydro · Hydro · 1 MW · Hawaii
• Puueo · Hydro · 3.1 MW · Hawaii
• Shipman · Oil · 15 MW · Hawaii
• Kanoelehua · Oil · 21 MW · Hawaii
• W H Hill · Oil · 37.1 MW · Hawaii
• Puna · Oil · 39.1 MW · Hawaii

Location

Coordinates 19.713, -155.1486 from WRI Global Power Plant Database (CC BY 4.0). View on OpenStreetMap.

Frequently asked questions