There are now more than two million solar installations in the U.S., and that number is set to double in four years, Reuters reported Thursday.

The announcement came as a joint statement from industry group the Solar Energy Industries Association (SEIA) and research firm Wood Mackenzie.

"We believe that the 2020s will be the decade that solar becomes the dominant new form of energy generation," SEIA CEO Abigail Ross-Hopper said in the statement, according to Reuters.

Solar energy now generates enough power to fuel more than 12 million homes, and the renewable energy source has made strides in recent years. It hit the one million mark only three years ago, a target it took the industry 40 years to achieve, CNBC reported. California was a major player in that growth. It was responsible for 51 percent of the first million installations and 43 percent of the second. Texas, Rhode Island, Florida, Utah and Maryland were also key players, SEIA said.