In a state blessed by an abundance of sun, one might expect the solar industry to bask in unmitigated regulatory support. But Arizona is not California, and the state’s homegrown controversy over rooftop solar has cast a dark cloud over the future of the market there.

Recently, the state’s power regulator opened a big hole in that cloud and let in a bucket of sunshine when it issued a ruling that is favorable to rooftop solar customers.

In August, the Arizona Corporation Commission (ACC) approved new rates for solar customers in the service territory of UniSource Energy Services (UNS), a small utility that provides electricity to about 90,000 customers in Mojave and Santa Cruz Counties. The new rates include minimal increases for customers. According to a statement by the ACC, the average residential customer will see an estimated increase of $4.20 in their monthly bill.

The utility had asked for more. The ACC approved a basic service fee of $15, five dollars less than the $20 UNS requested. It also rejected a request from UNS to require a demand charge for all solar customers.

Like other utilities in similar cases, UNS argued that, because of overly generous net metering rates, it is not able to recoup all of its costs for servicing customers with rooftop solar.

In making its ruling, the Commission kept an eye on consumers. The approved rate design includes a grandfathering clause for existing solar customers who are currently using net metering, to protect them from any future utility actions to lower the rate of compensation. It also creates incentives for customers to go from a standard two-part rate to a “Time-of-Use” plan. A three-part rate, which does include an optional demand charge, will also be offered to customers. At the Commission’s urging, UNS will also create an out-reach program to help consumers understand demand charges and how they can be used to save money.

The plan also includes an RPS credit for solar exports, starting at $0.11 per kilowatt-hour for a first allotment, or tranche. New customers can choose to lock in a 20-year contract at the going credit rate, which will be deducted from their utility bill based on how much they generate each month.

The new rates go into effect on September 1.