WASHINGTON -- Last October, the Obama administration announced plans to install solar panels on the roof of the White House by the spring of this year, returning the power of the sun to the pinnacle of prominence a quarter-century after Jimmy Carter's pioneering system was taken down.

Spring has come and gone, and the promised panels have yet to see the light of day.

Administration officials blame the complexities of the contracting process, and say the solar project is still an active one. But they can't say when it'll be complete.

Environmental groups say the symbolism is telling -- and disappointing.

"On we'll go," sighed Bill McKibben, founder of the climate activist group 350.org. "One more summer of beautiful, strong sunlight going to waste, just bouncing off the White House roof."

McKibben and other environmentalists say the failure to meet its own deadline reflects an administration that's been long on green rhetoric but sometimes disappointingly short on practical accomplishments.

In last fall's announcement, at a conference of government officials and environmental groups, Energy Secretary Steven Chu was specific. "I'm pleased to announce that, by the end of this spring, there will be solar panels and a solar hot water heater on the roof of the White House," he wrote that day on his departmental website.

Nancy Sutley, chairwoman of the Council on Environmental Quality, added that by installing the system on the most famous roof in America, President Obama was "underscoring (his) commitment to lead and the promise and importance of renewable energy in the United States."

McKibben, who along with other environmentalists had met with White House officials to urge such an installation, was surprised and gratified by the announcement a mere two weeks later. But the missed deadline has left him downcast.

"Nine months is a pretty long time. You can have a baby in that time," he said. "On the list of things that get done, this isn't all that hard. It doesn't require SEAL Team 6. It just requires a good-faith effort. You can just open the Yellow Pages and get page after page of solar installers."

Solar power advocates note that rooftop arrays are no longer the expensive oddity they were in Carter's day. Depending on their locations, homeowners can install systems that will pay for themselves over time.

Administration officials counter that the White House isn't just any old home.

"The Energy Department remains on the path to complete the White House solar demonstration project," Ramamoorthy Ramesh, head of the Energy Department's Solar Technology Program, wrote in a blog post late Monday, adding that further details and timing will be shared "after the competitive procurement process is completed."

Despite the missed deadline, officials maintain climate issues and energy conservation have been a top priority under Obama. They point to higher gas-mileage standards, green-tech incentives in the stimulus plan and presidential visits to wind turbine and electric-vehicle battery plants. Ramesh heads what's called the "SunShot Initiative," a competition that aims to slash the cost of solar power and make it "quicker, easier and cheaper to install."

But environmentalists look at Obama's plans to boost offshore oil drilling and the collapse of climate change legislation and say the administration's record is mixed. Especially for someone whose convention acceptance speech promised future generations would see his tenure as "the moment when the rise of the oceans began to slow and our planet began to heal."

The record on solar power at 1600 Pennsylvania Avenue began in June 1979, when Carter had 32 panels installed at a cost of $30,000 to provide hot water to West Wing offices. At the time, the Iranian revolution had thrown world oil markets into turmoil and a U.S. energy crisis was in full bloom.

Carter knew his solar panels were an experiment.

"A generation from now, this solar heater can either be a curiosity, a museum piece, an example of a road not taken, or it can be just a small part of one of the greatest and most exciting adventures undertaken by the American people," he said.

His successor, Ronald Reagan, was unimpressed. Aides had the panels removed and shipped to Unity College in Maine, where some of them remain.

Carter wasn't the only president to tap the sun's energy. In early 2003, without a big announcement, George W. Bush's administration had a modest system installed on the roofs of several maintenance buildings to generate small amounts of power for the White House complex and heated water for the mansion's outdoor pool.

Obama, in his public pronouncements, has aggressively promoted solar power along with wind and biofuels as ways of combatting global warming and weaning America off its expensive imported oil habit. He's also declared the federal government should "lead by example" on solar.

However, the administration has long known there might be federal contracting hurdles. To accompany the White House project announcement in October, the Energy Department published a handbook titled "Procuring Solar Energy: A Guide for Federal Facility Decision Makers." It ran to 104 pages.