Solar power You’ve seen the boxy blue panels on rooftops and street lights. Now get ready for a new kind of solar invasion. As the price of the technology comes down and the pressure to be environmentally friendly goes up, solar power is making its boldest move yet into America’s homes, cars and gadgets.

Industry boosters say new and cheaper “thin-film” panels are spurring more interest in home rooftop systems, and consumers can now use sun power to help to fuel lawn mowers, improve auto mileage and recharge portable devices, like cell phones and Bluetooth headsets. It’s even used to counteract its own effects, by cooling car cabins on a scorching summer’s day.

Despite the economic downturn, sales of solar panels for devices large and small grew nearly 50 percent to $22.5 billion in 2008. But while the number of panels sold is expected to keep rising this year, analysts expect sales in dollars to fall to $14 billion, as manufacturers pay much less for raw materials like polysilicon.

The upshot? Experts predict prices for solar cells will drop more than 30 percent this year. “Companies used to have an undersupply, and now there’s an oversupply,” says Robert Castellano, president of The Information Network, a tech-focused market-research firm.

But the news isn’t all sunny for consumers. With smaller products especially, the charging speed can often be described as glacial, depending on how much actual sunlight is available. (Pacific Northwesterners, take note.) Then there’s the robustness of the charges themselves; new solar-powered auto-mileage boosters, for example, claim to provide as much as 30 miles per day, but experts say they can peter out after as little as five, depending on driving style and road conditions.

As the market for solar-powered products evolves, we slather on some SPF 45 and set out to discover which products, if any, are ready for their moment in the sun.

HOME & YARD

Until a few years ago, eco-minded homeowners hoping to harness the power of the sun to save on electricity had pretty much one choice: heavy photovoltaic panels whose mounting often required punching holes in your roof – not to mention your bank account.

But when a $500 electric bill last summer motivated Emma Gonzalez of Fresno, Calif., to explore solar-energy options, she wanted no part of hefty panels or five-figure outlays. Taking advantage of one of the industry’s generous new financing options (no money down, payments starting at $100 per month), she flipped the switch on thin, black, frameless panels that, she says, don’t clash with her custom-colored mocha roof. After 15 years, Gonzalez adds, she’ll have the option to buy the system or upgrade to newer technology; at that point, she says, “they’ll probably be the size of a laptop.”

Gonzalez isn’t the only homeowner hoping to catch some moneysaving rays. Last year U.S. solar-panel installations surpassed 16,500 homes – double the number in 2006. Behind the surge are falling prices, fresh financing options, and government rebates and tax credits – along with the new, cheaper thin-film technology. According to the Solar Energy Industries Association, an average-size thin-film system might cost $13,500, versus $22,000 for traditional photovoltaic panels with comparable output.

Experts say thin-film technology is generally about half as efficient at converting the sun’s rays into electricity, meaning you’ll probably need more of the stuff on your roof. But because it can roll on as a flat sheet or coat individual shingles and roof tiles, it’s far less conspicuous than those chunky old-school panels. And the reality is, even a less-efficient system might still produce enough power to meet your needs – and more – while paying back your investment sooner. In the first three months alone, Gonzalez’s panels produced more electricity than she used, resulting in a small credit on her bill.

As the green-lifestyle drumbeat grows louder, solar products are migrating off the roof and into the yard-with mixed results. For eco-friendly lawn care, the Solaris cordless electric mower ($470) comes with an optional solar recharging station ($200). But the grass might grow pretty thick while you wait for it to power up; the company says it takes between two and five days, “depending on cloud conditions.”

And while numerous lawn and patio products-from basic garden lamps to burbling fountains  and lighted patio umbrellas-are now drawing their power from the sun, experts say their reliability can vary widely, depending, of course, on available sun and the technology used. Tony Clifford of Washington, D.C., recently installed a solar-powered motion-activated light to illuminate the front of his house when he fumbles for his keys at night. Yet even after plentiful charging, he says, it never lasted a full night: “It’s lying around someplace in the house.”

AUTOMOBILES

When it comes to cars, there’s a lot of eco-chatter about fuel alternatives involving electricity, hydrogen or even ethanol. But major carmakers have been noticeably quiet on the solar front, offering little beyond a higher-tech version of that old folding dashboard shade with the picture of the giant sunglasses.

Here’s how it works: Solar cells in the sunroof activate the car’s cooling system even when the engine’s not running – saving on gas-guzzling A/C when, say, you’ve parked too long in a shadeless spot on a hot day. Audi offers the option with its A8 and A6 sedans (starting price: $790), while Toyota is testing something similar in its 2010 Prius. Of course, there are cheaper, less elegant aftermarket options, like the AutoVent SPV, a sun-powered fan that hangs from a closed window-weather stripping included.

In the all-important mileage department, experts say cars will need to become much lighter and have significantly larger solar panels before they’ll be able to drive very far on a sun-soaked charge. The Prius’ solar cells, for example, generate only enough power for a 60-watt light bulb.

But that hasn’t stopped some manufacturers from lifting their gaze to the skies. French sports-car maker Venturi is tooling up to mass-produce its Eclectic model, a “zero-emission urban vehicle” with an optional solar roof that will provide – drum roll, please – an extra 1.24 miles on the road with each day of sun. It looks a little like a futuristic golf cart, seats up to three passengers and will cost $20,000 when released next year. But at top speeds of about 30 miles per hour, it’s likely to keep you in the slow lane.

For hybrid drivers looking for some extra mileage oomph, one company, Solar Electric Vehicles, has designed solar panels that affix to their rooftops and connect to both the existing hybrid battery and its own supplemental one. Available from $3,500 to $4,500, these do-it-yourself kits increase the distance certain hybrids can go before they switch from using electricity to gasoline.

While the company claims the kits offer fuel-economy improvements averaging between 17 and 29 percent for most hybrids, Vikram Dalal, professor of electrical and computer engineering at Iowa State University, calculates it slightly lower, closer to 15 to 20 percent. For his part, the company’s president, Greg Johanson, says, “It’s all in how you drive.”

MOBILE CHARGERS

When Brendan Burroughs gets behind the wheel, fuel economy is less of a priority than staying connected to his girlfriend and business associates via his iPhone. To do that, the 33-year-old Bostonian uses a solar-powered Bluetooth wireless speaker that soaks up rays while clipped to the visor of his car. Even though he parks in an indoor garage at work, Burroughs says that between the morning sun and his commute time, he has gone a month and a half without having to plug the device into the car lighter.

For most solar-device users, though, patience is a required virtue. Battery company Energizer, which is releasing its first solar chargers ($50-$100) later this summer, says the slower of the two models will take 21 hours to refill two common digital-camera batteries-not exactly bunny speed.

Another outfit, Solio, sells universal chargers that work for a wide range of devices, including cell phones, digital cameras, portable game players and GPS systems. While the company says its Solio Classic ($100) needs only one hour of direct, natural light – preferably peak midday rays – to provide up to 20 minutes of cell phone talk time or up to 50 minutes on a music player, it requires two full days to fully power up. One stipulation: Charging may take longer behind a tinted window or if any shadow falls on part of the solar panel.

Barney Wagman has experienced firsthand the joys and frustrations of relying on the sun’s power. When the 58-year-old cardiologist from Bethesda, Md., trekked for two weeks on the Himalayan peak of Annapurna, he loved having Bob Dylan and Allman Brothers tunes with him in the remote mountain terrain, courtesy of a solar charger he clipped to his backpack. But clouds usually rolled in by noon each day, forcing him to restrict his iPod time to only the very toughest parts of the trek. He’s hoping it will work better on his next hiking trip, to Slovenia. There, he expects, “we’ll have more sun.”

2009 Copyright The New York Times Syndicate