4) Hydropower is the biggest renewable source, at 7 percent of electricity
This map shows hydroelectric dams around the country:
Hydropower is still, by a fair margin, the biggest source of clean renewable power in the United States. As of 2015, there were more than 1,420 hydroelectric dams providing 7 percent of the nation’s electricity.
But not all dams are equal. The massive dams in the West provide a disproportionate amount of electricity — Washington, home of the Grand Coulee Dam, produces nearly one-third of the nation’s hydropower. The Hoover Dam in Nevada is another huge one. Then there’s a vast array of smaller dams around the country providing more modest jolts of power.
It’s unlikely that the United States will ever build any more gigantic dams — most of the best sites are already tapped, and dams can be controversial. (No one’s going to dam up the Grand Canyon.) If anything, there’s been a push in recent years to tear down some older dams that have ravaged ecosystems — like the 108-foot Elwha River dam in the Pacific Northwest, dismantled in 2011 to ease salmon flows.
Still, given our quest for carbon-free power to avert global warming, hydropower will always attract some interest. In 2013, Congress passed a bill aiming to eke more power out of smaller rivers and streams by adding generating capacity to existing dams.