Santa Rosa's newest solar array appears to have a lot going for it.

The panels are highly efficient, installation was a snap, and best of all it didn't cost city taxpayers anything.

There's just one problem: the 345 panels were made by a company with dirtiest name in the clean energy business — Solyndra.

The Fremont-based solar manufacturer is now bankrupt. Repayment of its $535 million federal loan is in doubt, an FBI investigation is underway and its state-of-the-art facility in the East Bay that once held promise as a generator of green manufacturing jobs is shuttered.

Santa Rosa officials say the selection of Solyndra's unique panels was made in January, well before the company's financial troubles became apparent. The company's technology was sound, its costs competitive and the panels well-suited for the white roof on which installation is nearly complete.

But the company's demise leaves the city wondering who will back the 25-year warranty for the panels. Solyndra promised refunds for products that fail to perform at 80 percent of their power rating.

"We are a little anxious about any performance warranty and who will be picking that up as they restructure under bankruptcy," said Dell Tredinnick, project development manager for the city's utilities department.

The array went up late last month on the roof of the administration building at the city's Laguna Treatment Plant. It is expected to go into service soon, after some interior wiring work is complete, said Colin Close, research and program coordinator for the city utilities department.

Unlike the other arrays at the treatment plant, which were funded through water and sewer rates, the Solyndra product was made possible through a $1.5 million Department of Energy grant bolstering energy efficiency and conservation projects. The money was part of the $840 billion federal stimulus package, the American Recovery and Reinvestment Act of 2009.

So, U.S. taxpayers were supporting Solyndra on both ends, subsidizing its operations through a federal loan guarantee, and aiding its sales with stimulus funds. Despite these subsidies, analysts have said the company couldn't compete as the recession and increasing overseas production created a glut of low-cost silicon solar panels.

Close said it's merely a coincidence that the city spent its stimulus funds on a solar panel whose manufacturer also received stimulus funds. The Department of Energy, which managed the grant, was "hands off" about what technology the city chose, and did nothing to steer the city toward Solyndra's products, Close said.

"It would be very interesting to see how many cities did solar and how many of them went with Solyndra," Close said.

Santa Rosa spent its $1.5 million on more than a single solar array. The city has funded or plans to fund seven energy-related projects with the money.

The other city projects included: installing electric vehicle charging stations, funding a regional building retrofit program, improving signal lights on Santa Rosa Avenue, installing high-efficiency street lights, offering rebates for weatherizing low-income housing and studying the city's greenhouse gas emissions.

The total cost of the Solyndra project was $348,477, or 23 percent of the grant. The cost included an engineering analysis of the administration building's roof to determine the load it could bear.

The 35,000-pound limit became one of the key reasons for the decision to go with the lightweight Solyndra array.

The city also wanted one that would not penetrate the white surface of the building's new "cool roof," which keeps cooling costs down by reflecting the sun's rays. High efficiency, low cost and ease of maintenance were also desired. The stimulus funds also required the panels be made in America.

MKM & Associates, a structural engineering firm, evaluated the criteria and concluded that Solyndra was the only manufacturer that met all of the local and state requirements.

Some traditional flat panels of crystalline silicon solar cells can generate more power at peak hours, the city's consultant said. But Solyndra panels, because of their cylindrical shape, absorb light from all directions and have better performance earlier and later in the day when the sun's rays are less direct. For this reason, they work well on reflective white roofs, the city was told.

Each Solyndra unit is made up of 40 glass cylindrical tubes. Inside each is a smaller tube coated with the company's copper-indium-gallium-diselenide (CIGS) thin films.

After choosing Solyndra, the city put the purchase out to bid. A Modesto solar firm, Panelized Solar, won the contract and the panels were installed by Solar Universe of Santa Rosa.

If they work as expected, the array should produce 105,000 kilowatt hours per year, about as much used by 16 average homes. That should save the city $18,500 per year over the life of the system and prevent the emission of 54 tons of carbon annually, Close said.

The estimate assumes the cost of electricity continues to rise at about 5 percent per year. It also factors in the costs of maintenance and a decrease in system performance over its life. It also assumes the warranty will be honored, which the company says it intends to do.

If Solyndra doesn't survive, Close said he thinks another company will acquire the assets because everything points to the technology being sound.

"Because we have not heard anything negative about the technology, we're hopeful that it's going to be very productive over the long haul and its going to help stabilize rates for our ratepayers," Close said. "We don't have any reason to believe it won't."