Solar panels on the White House roof became operational Friday as President Barack Obama unveiled hundreds of measures to expand the use of clean-energy sources in front of a crowd gathered at a Walmart department store in Mountain View, California — a location chosen for its commitments to renewable-energy efforts.

Obama told the crowd that the transition to “a clean-energy future” would create jobs and reduce U.S. dependence on foreign oil.

In a largely symbolic gesture to show his personal commitment to reducing the U.S.'s carbon footprint, Friday also saw the White House go live with reinstalled solar panels

Former president Jimmy Carter first installed the panels in 1979 amid the Arab oil embargo that caused a nation-wide energy crisis. At the time, he said they could either serve as an “example of a road not taken” or “a small part of one of the greatest and most exciting adventures ever undertaken by the American people.”

One of the first acts undertaken by his successor, Ronald Reagan, was to remove the solar panels and recommit the nation to fossil fuels because, as his chief-of-staff explained, Reagan felt solar power was "just a joke."

“Solar panels on the White House are a really impressive message: solar is here, we are doing it, and we can do a lot more,” Ernest Moniz, secretary of energy, said in a video posted Friday on the White House website. “The clean energy revolution is not something for the distant future — it’s happening right now.”

Every four minutes, a small business or homeowner is going solar, Cyrus Wadia, of the White House Office of Science and Technology Policy, said in the video.

“In a sense, we’re going through a transition here … that we are just seeing the beginning of,” Wadia said.