Utility commissioners in Arizona will decide the fate of rooftop solar incentives this week, in what has become the biggest fight over renewable energy policy in the country. A two-day hearing on the issue at the Arizona Corporation Commission began Wednesday.

The Arizona Public Service, the state's largest utility, is asking the commission to change the current policy, which allows homes and businesses with their own solar power systems to sell any excess energy they generate back to the grid. That policy, known as net metering, was first put in place in 2009. The utility argues that customers with rooftop solar aren't paying their fair share to maintain the grid, and has proposed policy changes that would increase prices for those with solar systems. But local solar advocates have accused the utility of trying to kill the state's burgeoning solar industry, and have launched a counter-campaign.

As The Huffington Post has previously reported, the fight got interesting when the utility revealed that it had been secretly funding anti-solar ads produced by a national conservative group. After a commissioner asked the company and other groups involved in the net metering debate to disclose how much money they were spending on the issue, APS disclosed that it had spent $3.7 million on PR work. The solar lobby disclosed that it was spending nearly half a million dollars on fighting the proposed changes.