Because few new hydro plants are expected to come online in the next two years, hydroelectric generation in 2018 and 2019 will largely depend on precipitation and water runoff. Although changes in weather patterns also affect wind generation, the forecast for wind power output is more dependent on the capacity and timing of new wind turbines coming online.
Both hydro and wind generation follow seasonal patterns. Hydro generation is typically highest in the spring when precipitation and melting snowpack increase water runoff. Wind generation is typically highest in the spring and fall, reflecting the capacity-weighted mix of seasonal patterns in wind across the country. Hydro often has slightly higher annual capacity factors, or utilization rates, averaging 38% in 2016 compared with wind’s 35%.
EIA’s hydroelectric generation forecasts over the next two years are mostly based on projections of water runoff. After a relatively wet year in 2017—when hydro provided 7.4% of total utility-scale generation—hydro generation is expected to be slightly lower at 6.5% of total utility-scale generation in 2018 and 6.6% in 2019.Because much of the new electric capacity comes online in the final months of each year, these capacity additions affect the subsequent year’s electricity generation values. EIA expects wind to provide 6.4% and 6.9% of total utility-scale electricity generation in the United States in 2018 and 2019, respectively, up from 6.3% in 2017.
Principal contributor: Owen Comstock