Definition: The capacity factor represents the expected annual average energy production divided by the annual energy production, assuming the plant operates at rated capacity for every hour of the year. Capacity factor is intended to represent a long-term average over the lifetime of the plant; it does not represent interannual variation in energy production. Future year estimates represent the estimated annual average capacity factor over the technical lifetime of a new plant installed in a given year.
The capacity factor is influenced by site hydrology, design factors (e.g., exceedance level), and operation characteristics (e.g., dispatch or run-of-river). Capacity factors for all potential NPD sites and NSDs are estimated based on design criteria, long-term monthly flow rate records, and run-of-river operation.
Recent Trends: Actual energy production from about 200 run-of-river plants operating in the United States from 2003 to 2012 (EIA, 2016) is shown in the historical chart below. This sample includes some very old plants that may have lower availability and efficiency. It also includes plants that have been relicensed and may no longer be optimally designed for current operating regime (e.g., a peaking unit now operating as run-of-river). This contributes to the broad range, particularly on the low end. Interannual variation of hydropower plant output for run-of-river plants may be significant due to hydrological changes such as drought. This impact may be exacerbated by climate change over the long term.
Base Year: Base Year capacity factors for new hydropower plants are assumed to be near the 80th percentile of the historical range, with a small range, and reflect site-specific expectations for future hydropower plants.
Future Years: The capacity factor remains unchanged from the Base Year through 2050. Technology improvements are focused on CAPEX and O&M costs.
The following references are specific to this page; for all references in this ATB, see References.
EIA (2016). Capital Cost Estimates for Utility Scale Electricity Generating Plants. U.S. Energy Information Administration. https://www.eia.gov/analysis/studies/powerplants/capitalcost/pdf/capcost_assumption.pdf