Why hydropower is the forgotten giant of clean energy

Hydropower is by far the largest renewable worldwide, producing over twice as much energy as wind, and over four times as much as solar. And pumping water up a hill, aka “pumped storage hydropower”, comprises well over 90% of the world’s total energy storage capacity. 

But in spite of hydropower’s outsize impact, we don’t hear much about it in the U.S. While the past few decades have seen wind and solar plummet in price and skyrocket in availability, domestic hydropower generation has remained relatively steady, as the nation has already built hydropower plants in the most geographically ideal locations.

Internationally, it’s a different story. China has fueled its economic expansion by building thousands of new, often massive, hydroelectric dams over the last few decades. Africa, India, and other countries in Asia and the Pacific are set to do the same.

But expansion without strict environmental oversight could lead to trouble, as dams and reservoirs disrupt river ecosystems and surrounding habitats, and recent studies show that reservoirs can emit more carbon dioxide and methane than previously understood. Plus, climate-driven drought is making hydro a less reliable source of energy, as dams in the American West have lost a significant amount of their electricity generating capacity.

“In a typical year, Hoover Dam will generate about 4.5 billion kilowatt hours of energy,” said Mark Cook, Manager of the iconic Hoover Dam. “With the lake being the way it is now, it’s more like 3.5 billion kilowatt hours.”

Yet experts say that hydro has a big role to play in a 100% renewable future, so learning how to mitigate these challenges is a must.