As the recession wears on, there's a lot of enthusiasm for renewable energy's potential to create jobs.

This economy, proponents say, promises to rebuild communities abandoned by bankrupt manufacturers, restore jobs lost by the busted housing market and reinstate America as a global leader.

Not so fast.

Although Senate Majority Leader Harry Reid says renewable energy has the potential to create "tens of thousands of jobs" in Nevada and more than a million nationwide, little research has been done on actual job creation in such an unchartered area.

"The real detailed work has not been done," UNLV economist Keith Schwer said. "A lot of unknowns are in front of us."

Such as how many of those are temporary construction jobs, and how many are long term.

Reid spokesman Jon Summers said the Nevada Democrat's office is looking into how many of those jobs would be temporary, and how many translate into permanent employment.

Although it's a stretch, the renewable energy push has been likened to President John F. Kennedy's national challenge to put a man on the moon.

Congress is considering expansive energy legislation and is expected to take up the issue after its August recess. The House passed a bill June 26 that mandates an increase in the percentage of renewable energy utilities must use to generate electricity to 15 percent by 2021. It also contains grants for green jobs. The Senate is considering similar legislation.

Schwer compared renewable energy to the industrial revolution, which brought about technological changes, but pushed out established industries.

"It created new jobs, but it also killed jobs," he said.

"There's a lot of problems we face ... when there are large numbers of unknowns and perhaps a lot of misspoken statements," Schwer said.

But if renewable energy lowers energy costs as proponents say it will, that would free up money for consumers to spend elsewhere, he said.

Just as Spain opened the New World to Western discovery, it also is one of the leaders in the green energy frontier.

Green energy jobs could kill other energy jobs at a rate higher than new jobs are created, said a study by Rey Juan Carlos University in Madrid.

The Spanish study showed that should the U.S. continue to follow the European model, it can expect to lose nine jobs for every four created.

Of the jobs created in Spain two-thirds were in construction, fabrication and installation and one-quarter in administration, marketing and projects engineering. One out of every 10 jobs created was a permanent position in operation and maintenance, the study said.

It concluded that, based on Spain's high subsidies for of its green energy initiatives, the country spent $823,000 to create each green job, based on the current exchange rate. In the wind industry, it cost $1.4 million per job. Overall, Spain spent $36 billion subsidizing solar, wind and minihydro, the study said.

Each megawatt created from a green energy source cost about five jobs within the general economy, the study said. A megawatt created from photovoltaic solar caused the loss of nine jobs; wind energy, four jobs; minihydro, five jobs.

"These costs do not appear to be unique to Spain's approach, but instead are largely inherent in schemes to promote renewable energy sources," the study said.

If the cost of renewable energy forces consumers to pay more for electricity, as was the case in Spain, businesses could move elsewhere, the study said.

But the naysayers have their own naysayers.

So far, 750,000 renewable energy jobs have been created without sustained government investment, reported the Center for American Progress, a think tank.

From 1998 to 2007 jobs in clean energy grew at a national rate of 9.1 percent while traditional jobs grew by 3.7 percent, according to the think tank Pew Charitable Trusts.

Colorado Gov. Bill Ritter Jr. is an advocate of clean energy, especially as it benefits his state.

Using its history as a manufacturing state, Colorado has attracted a wind turbine producer that is expected to employ 2,500 workers, Ritter testified July 21 before the Senate Environment Committee and the Green Jobs and New Economy Subcommittee.

"Just as the industrial revolution created the jobs of the 20th century, we now usher in a new century of innovation, creativity and entrepreneurial vigor," he said. "The new energy economy is creating the pathway to these careers and a new American century of energy leadership."

The data are mixed, and it's difficult to find a balanced study, said economist John Restrepo, principal of Restrepo Consulting Group.

Although Nevada has the potential to house solar, wind and geothermal plants, there is always the possibility the facilities will be built elsewhere.

"You ask where the research is and everyone starts looking at their shoes," Restrepo said. "The jury's still out, so to speak."