The batteries will ensure customers don't set a high, momentary demand for power that will trigger steep fees from the utility.

SRP officials said the utility's new rate design will encourage customers to reduce their maximum demand on the utility grid. In the Phoenix area, the highest electricity use occurs in late summer afternoons, when air-conditioners crank up and, unfortunately, the sun is low in the sky and solar panels are not at their maximum output.

"If Arizona residents want to go solar, we are committed to finding a solution," American Solar and Roofing President/CEO Joy Seitz said. "It took a lot of manpower we had to invest to find a solution. I wouldn't say (SRP) was right (to charge higher solar fees), but in the world of running a business, you either play the game or leave.