Utilities have used hydropower storage for nearly a century, pumping water into mountaintop reservoirs when energy demand is low and releasing that water to generate electricity at peak times. Compressed air thermal storage has also been used.

But while batteries have been around since the 19th century, they have not played a major role in the U.S. power grid until very recently thanks to rapidly-falling prices for lithium-ion batteries.

“The cost of storage has come down much more rapidly than most people anticipated,” Werner said. “We’re expecting to see that more and more.”

As of December, there were 119 utility-scale batteries with a combined capacity of 845 megawatts deployed nationwide, according to the EIA. Only two dozen of those are larger than 10 megawatts.

According to the International Energy Agency, storage is a crucial component to limiting the rise of global average temperatures.

The Wisconsin PSC is currently evaluating proposals for 300-megawatt and 150-megawatt solar farms and has received pre-application materials for three other solar projects with a combined capacity of 449 megawatts.