SAN FRANCISCO — The shingles that help to protect you from the elements could soon help to keep your lights on. Solar companies have developed light-absorbing roof tiles as a more aesthetically pleasing alternative to solar panels.

Making solar materials better looking is the key to millions of American actually installing them on their rooftops, according to one executive. Those roofs are a “Persian Gulf of energy potential,” said Dan Shugar, president of PowerLight.

At the Solar Power 2004 conference in San Francisco, solar vendors, including PowerLight, showed off integrated building materials that convert the sun’s rays to electricity.

The market for solar energy, which has relied on rigid photovoltaic panels, has grown 30 percent a year, according to Solar Energy Industries Association, the trade group that organized the show.

Photovoltaic solar panels, which were invented in 1954, consist of grids of raised black cells that have been criticized as aesthetically unappealing. Some homeowners have also been reluctant to embrace the technology because installing solar panels may require puncturing an existing roof and bolting on metal supports, which can void the roof’s warranty, according to Shugar.

PowerLight’s PowerGuard rooftop system molds photovoltaic panels into roof tiles that can be snapped onto an existing roof without puncturing its surface, according to Shugar. This extra layer is more visually appealing than standard photovoltaics, and adds two layers of insulation that can extend the life of the roof to 30 years, he said.

Solar panel manufacturers Sharp Electronics, Konarka Technologies and United Solar Ovonic also presented solar roofing materials at the conference.

The fact that Sharp, which manufactures three times more solar panels than any other company, is interested in solar roofs indicates the technology will likely take hold, according to Ron Pernick, founder of clean-energy consulting company Clean Edge.

“I have no doubt that deriving solar power from the roof itself is the wave of the future,” Pernick said. Solar roofing materials are likely to be most popular with new construction because minimal additional labor cost would be involved, he said, although retrofitting houses with solar roofs is also viable.

Pernick said solar roofs would probably be adopted most quickly in states such as Hawaii and California where the cost differential between electricity derived from solar and fossil fuels is not as great.

Government officials in California have encouraged the use of solar energy in the state. San Francisco Mayor Gavin Newsom told event attendees that the city is constructing 1,600 homes with solar panels in its Bayview-Hunters Point neighborhood. Newsom said now is the time to start addressing global warming by installing solar panels on roofs. “We can sit here and just talk about it while we continue to get clobbered, or actually do something about it,” he said.

California Gov. Arnold Schwarzenegger has proposed that 1 million homes in the state install solar power systems by 2010, but the state assembly failed to pass the necessary legislation, according to Newsom. Newsom expects the state will pass the measure during its next legislative session.

One company is aiming its product at the consumer who lives in “low light” conditions. Konarka’s integrated roofing material uses plastic sheets of polymer materials instead of silicon-based panels. The flexible plastic “is more efficient at low light, such as when the sun is rising or setting, on cloudy days,” so it may be better for certain areas, according to Dan McGahn, executive vice president. It converts 5 percent of the solar energy into electricity, compared to silicon-based systems that are 15 percent to 20 percent efficient, and costs about twice as much as a standard roof.

McGahn said his company’s technology can also be integrated into a variety of materials for products such as laptops, cell phones and even clothes.

Konarka is still developing its roofing material technology, and has not announced when it will be commercially available. Sharp said it would have product available in 2005, and United Solar Ovonic is currently accepting orders. Representatives from solar panel manufacturers BP Solar, Shell Solar and RWE Schott Solar said their companies are not currently developing integrated roofing materials for the U.S. market.

Konarka’s McGahn said it’s not likely solar will capture a large share of the electricity market anytime soon. Global solar panel manufacturing capacity won’t catch up to demand for at least a year, he said, and grabbing just 10 percent of the electricity market would require $270 billion of investment in production facilities.