Washington, D.C., Mayor Muriel Bowser (D) signed into law on Jan. 18 one of the most ambitious 100 percent clean energy mandates in the U.S., surpassing the renewable-energy goals of New York state, California, and Hawaii.

The D.C. Council unanimously passed the Clean Energy D.C Omnibus Act of 2018 in December 2018. The law that Bowser signed Jan. 18 requires all electricity sold in Washington to come from wind, solar, and other clean energy sources by 2032....