Researchers at the U.S. government’s National Renewable Energy Laboratory have built flexible solar cells using a thin and pliable kind of glass from Corning, the company that makes the glass that covers iPhone screens. The new solar cells could make rooftop solar power far cheaper.

Based on tests by Corning, which makes a product called Gorilla glass for iPhone screens and which announced the flexible material, called Willow glass, last year, shingles made from such solar cells could last for decades on a roof—even weathering hail greater than three centimeters in diameter. Conventional solar panels are heavy, bulky, and breakable, which makes them expensive to transport and install.