Arizona voters have rejected a measure requiring regulated utilities to obtain 50 percent of their electricity from renewable energy sources like solar or wind power by 2030.
Proposition 127 was fiercely opposed by the state's largest utility, Arizona Public Service.
The utility's parent company spent more than $25 million to oppose the measure, arguing it would raise consumer costs by as much as $1,000 a year per customer annually and hurt the reliability of the state's electrical grid.
The Clean Energy for a Healthy Arizona proposal was backed by solar advocates in Arizona with funding from San Francisco billionaire Tom Steyer.
Initiative supporters say Arizona hasn't taken advantage of its role as the sunniest state in U.S. to develop more solar energy. California's Legislature enacted a similar measure in 2015.