Solar system installer Thomas Bywater adjusts new solar panels on the roof of a house in Sydney, August 19, 2009. REUTERS/Tim Wimborne (Reuters) - In a first on Monday, an online marketplace will allow U.S. homeowners to weigh options for going solar as easily as they can compare prices for airline tickets.

Geostellar, a startup backed by power producer NRG Energy Inc, is seeking to become the Expedia or Orbitz of the solar industry -- a one-stop shop where consumers can not only compare the benefits of leasing solar panels versus buying them outright, but ultimately sign up to install a system.

Solar players including NRG, No. 1 U.S. installer SolarCity Corp, Boston-based solar loan provider Admirals Bank, manufacturer and financier Conergy, East Coast installer Roof Diagnostics and Connecticut's Clean Energy Finance and Investment Authority will feature their products on the site, www.geostellar.com.

Geostellar hopes its platform will allow installers and financiers to lower the cost of acquiring new customers -- a major goal in the fiercely competitive rooftop solar industry. Solar companies are laser focused on slashing costs so that they can deliver on their promise to save customers money on power bills by going solar.

Geostellar will make money by claiming a portion of a system's total installed price - between 10 and 20 percent, Chief Executive David Levine said.

Geostellar, which was founded in 2010, got its start by selling data to solar companies that showed the solar energy potential of individual rooftops. Its early customers included solar financing companies SunRun, Sungevity and others, according to Levine.

In May 2012, it raised $14 million from NRG, Flash Forward Ventures, satellite imagery company GeoEye (now owned by DigitalGlobe Inc), and the state of Maryland's venture capital fund.

Levine, who had tried to convince his customers to use Washington-based Geostellar's data to build a website where consumers can comparison shop for solar, resolved to use those funds to build it himself.

"We went back to those customers and said instead of us giving you data and you doing themarketing, we want to be your customer acquisition engine," Levine said in an interview.

Geostellar uses satellite data to build 3D representations of neighborhoods and their rooftops. A simulation that moves the sun across the sky then helps the company calculate how much sun a rooftop gets at any particular time of the year - a key factor in determining whether going solar makes financial sense. The website then layers on the value of government incentives as well as local utility rates to give customers a detailed view of what it would cost to sign up for a solar installation.

Depending on the market, visitors to Geostellar's website, or its mobile app called Solar Mojo, can then compare and contrast the costs and benefits of a solar lease, a lending plan or a cash purchase. Finally, they can sign up for what they want with the click of a button.

A solar lease allows customers to pay a monthly fee to go solar with no money down, but the homeowner does not own the panels. A loan allows for payments to be spread out over many years, but the homeowner does own the panels, providing eligibility to a federal tax credit worth 30 percent of the value of the solar system but also meaning the homeowner must monitor and maintain the panels.

Upfront cash purchases typically run between $20,000 and $30,000 for the average home.

(Reporting by Nichola Groom; Editing by Leslie Adler)