Clambering across the sloped roof of King’s College Chapel with the agility of an undergraduate, Toby Lucas, 56, pointed to where his craftsmen had welded solar panels to an expanse of newly installed lead. It was the scariest part of the project, he said, because an errant spark could have ignited the 500-year-old timbers underneath, which hold up the roof of this English Gothic masterpiece.

“It’s an iconic landmark in Cambridge, and it’s part and parcel of where I live,” said Mr. Lucas, whose firm, Barnes Construction, did the restoration. “You don’t want to be the person who is responsible for burning part of it down.”

The chapel came through the project unscorched and now stands at the heart of Cambridge University, no longer just a glorious relic of the late-medieval period but also a cutting-edge symbol of the green-energy future. Its 438 photovoltaic panels, along with solar panels on the roofs of two nearby buildings, will supply a shade over five percent of the college’s electricity.

King’s College Chapel is one of several landmark houses of worship in England that have installed solar panels in recent years. The cathedrals in Salisbury and Gloucester have them, and this project may open the door to more: A neighboring Cambridge college, Trinity, is contemplating whether to put photovoltaic panels on the roof of its chapel, which dates to the 16th century.

But this being a college town, and King’s College Chapel being such a nonpareil work of architecture, the debate over installing panels was long and lively — a heady mix of aesthetics, economics and politics. Even now, with the scaffolding dismantled and the panels beginning to soak up the late-winter sunlight, critics are eager to point out why the project was a mistake.