Hydro power plant in South Carolina, United States of America. Approximate location 35.0314, -81.4936.
HydroSouth CarolinaUnited States of America
99 Islands is a 12 MW hydro power plant in South Carolina, United States of America. It is operated by Duke Energy Carolinas LLC. Based on reported annual generation of 68 GWh, it can supply roughly 19k homes. It ranks #5419 of 10,938 United States of America power plants by installed capacity. Commissioned in 1910, it is around 116 years old — an older, legacy facility. 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 USA0003272.
Known, modelled and calculated values are kept separate. Missing fields are shown as unavailable.
The capacity and/or fuel fields on this page include a source-backed provenance label from GEM, an official registry, Wikidata, OSM, or a cross-source match.
capacity: Wikidata P2109 nameplate capacity; fuel: WRI source-record fuel
At 12 MW, 99 Islands 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.
Annual generation (GWh), WRI Global Power Plant Database (CC BY 4.0).
Operated by Duke Energy Carolinas LLC. All plants by this company →
This hydro plant converts the energy of falling or flowing water through hydro turbines. It sits in a humid subtropical climate (Köppen Cfa) — Northern Hemisphere, latitude 35.0°N — which shapes how much energy it can produce and how its output varies through the year.
Monthly mean temperature
Heating degree-days here run 31% below the median power plant in this dataset — a proxy for how much extra energy heated equipment must replace through its surfaces in winter.
Climate heat-demand index: 38/100 — this site sits in the mid third of the power plants we cover by heating degree-days.
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.
For a plant’s outdoor hardware — heat-recovery steam generators (HRSG), expansion joints, valves, flanges and their insulation — the local climate sets how fast unprotected steel and coatings degrade. This site sits in a moderately corrosive environment (estimated ISO 9223 class C3 — Medium), with humidity / wetness the leading environmental stress.
Higher environmental severity is exactly where protective removable insulation pays back most: a sheltered micro-climate slows corrosion, UV and thermal-cycling damage and extends outdoor hardware service life. This is an indicative site-climate context — not a condition assessment of any specific plant or operator.
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.
The #593 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.
Coordinates 35.0314, -81.4936 from WRI Global Power Plant Database (CC BY 4.0). View on OpenStreetMap.
99 Islands is a 12 MW source-record hydro power plant in South Carolina, United States of America, commissioned in 1910.
99 Islands generates about 68 GWh of electricity per year.
Its output is enough to supply roughly 19,314 homes.
99 Islands is operated by Duke Energy Carolinas LLC.
