Among generators that do not primarily rely on fossil fuels, nuclear plants are the most efficient — they ran at 92.3 percent of their capacity in 2015 — followed by hydroelectric at 35.8 percent
that year and wind at 32.2 percent, according to the Energy Information Administration.
According to the Energy Information Administration, conventional hydroelectric generating capacity stood at 78,956 megawatts in 2015,
while wind, the industry group says, reached 82,183 megawatts last year, about enough to run 24 million average American homes.
But hydroelectric power could still lead in terms of actual production: According to the Energy Information Administration’s most recent annual electric power report, hydroelectric
edged out wind in terms of power sent to the grid by roughly 30 percent in 2015, though both forms trailed fossil fuels and nuclear power by wide margins.
The wind industry crossed an important threshold in the United States last year, exceeding the generating capacity of hydroelectric
power for the first time, according to the main industry trade group, the American Wind Energy Association.