Why hydropower is the world’s most overlooked renewable

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.

In 2021, hydropower accounted for about 6% of utility-scale electricity generation in the U.S. and 32% of renewable electricity generation. Domestically, it was the largest renewable until 2019, when it was surpassed by wind.

The U.S. isn’t expected to see much hydropower growth in the coming decade, in part due to the onerous licensing and permitting process.

“It costs tens of millions of dollars and years of effort to go through the licensing process. And for some of these facilities, particularly some of the smaller facilities, they just don’t have that money or that time,” says Malcolm Woolf, President and CEO of the National Hydropower Association. He estimates that there are dozens of different agencies involved in licensing or re-licensing a single hydropower facility. The process, he said, takes longer than licensing a nuclear plant.

Because the average hydroelectric plant in the U.S. is over 60 years old, many will need to be relicensed soon.

“So we could be facing a raft of license surrenders, which is ironic just as we’re trying to ramp up the amount of flexible, carbon-free generation we have in this country,” Woolf said.

But the Department of Energy says there is potential for domestic growth, through…