Do the photovoltaics that can transform sunshine into electricity require a revolution? Our current Secretary of Energy and Nobel Prize–winner Steven Chu thinks so.

But Subhendu Guha, chairman of PV maker Uni-Solar, disagrees: "People say we need a revolution to get to grid parity. The revolution has already happened."

Uni-Solar manufactures thin-film solar cells made from amorphous silicon. The company has built a machine in Auburn Hills Michigan that churns out nine miles of such photovoltaics in 62 hours—and Guha hopes to make the revolutionary machine even bigger soon.

Uni-Solar is not alone. Manufacturers that make traditional crystalline silicon solar panels are boosting efficiencies and dropping prices thanks to equipment improvements plus cheap Chinese labor and materials. Another U.S. company, First Solar, claims it can make its variety of thin-film solar cells for less than $1 per watt.

That's been the goal of solar panel makers for a long time, because as those prices decline electricity from the sun costs the same as, or is even cheaper than electricity from burning fossil fuels. And that means a "deployment revolution" might be imminent or, as Guha says, "a roof is a terrible thing to waste."

—David Biello