The fight over whether Arizonans get to vote on a renewable energy measure is becoming very expensive.

New reports filed with the Arizona Secretary of State's Office shows that the initiative, Clean Energy for a Healthy Arizona, has collected nearly $8 million. And almost every penny of that has come from a political action committee set up by California billionaire Tom Steyer.

The report drew criticism from the spokesman for Arizonans for Affordable Electricity, the group that’s fighting the measure and has already amassed more than $11 million of its own — and all of that money comes from Pinnacle West, the parent company of APS.

If the Clean Energy initiative gets on the ballot, it would require most utilities to generate 50 percent of its energy from renewable sources by 2030.