Although the solar panels have been mounted on the building's roof for a while, the full system wasn't ready to go until now.

CPS Energy and Pearl were partners in the project, with Pearl contributing $950,000 and CPS throwing in $400,000.

The 200-kilowatt solar installation will generate about one-fourth of the building's energy needs overall and as much as one-third of the power on hot, sunny days, officials said.

“We'll be able to see what a solar array of this size can do to offset the energy demands of a big building,” CPS Energy CEO Milton Lee said. “And we'll be able to see how much energy this building produces on its own.”

That information will be valuable as CPS drives toward its goal of having sustainable energy supply 20 percent of the city's power by 2020, Lee said. The 67,000-square-foot Full Goods Building, which once housed the brewery's finished beer, is now a mixed-use structure that includes retail, restaurant and residential space.

Officials also showed off the project's snazziest feature: an interactive display for the public that shows how much power the solar panels are producing, what power the building is drawing and how much electricity is coming from CPS. The display also shows the amount of pollutants being avoided.

The interactive display is located in the building's breezeway, but a Web site,http://pearl.kiosk-view.com, makes it possible for anyone with a computer to see the same information.

“This is a learning lab, not just for CPS, but really for everybody,” said Bob Sohn, senior adviser for Pearl Planning. “Our hope is that others will replicate what we're doing.”

When the system produces more power than the building needs, the excess electricity will be fed back to CPS. The solar array was designed and installed by Meridian Solar of Austin.

At 1:45 p.m., the display showed that the solar panels were producing 93 kilowatts, while 39 kilowatts were coming from CPS to meet the building's total demand of 132 kilowatts.

Pearl's solar project is being unveiled at a time when CPS is looking to build its first large-scale solar project and deciding whether to spend billions to add two reactors to the South Texas Project nuclear plant.

CPS has said it may have to slash its goal of adding a 100-megawatt solar plant in half because the cost of adding solar remains high.

But Lee stressed that CPS remains committed to renewable energy. Renewable resources, mostly wind, are expected to provide 13 percent of CPS' peak demand this summer, he said.