The United Kingdom's largest drugmaker is constructing the U.S.' largest solar rooftop at its Southeastern Pennsylvania distribution center, Bloomberg reports.

GlaxoSmithKline will install 11,000 solar panels to generate 3 megawatts, which will power the York building for an entire year, reduce energy costs, and slash greenhouse gas emission. Suntech Power Holdings Company will manufacture the panels.

"This is just the beginning of a four-part strategy to go solar," Larry Brown, a vice president of the London-based company, told Bloomberg. "By the end of 2014 we'll be 100 percent powered by solar."

By the end of 2011, the company intends to embark on installing a 3-megawatt solar system at its Pittsburgh plant, which is the base of its U.S. operation, he said.

The company retained American Capital Energy to assist with the York building's rooftop. The Massachusetts company also assisted with a 700-kilowatt system this past March at its distribution center in Fresno, California.

The York building going solar will earn the drugmaker a $1 million Pennsylvania grant and $4.1 million in federal tax grant credit.