Automakers install solar panels on such cars as Prius, Audi A8

— -- Even as skies are gray this winter, automakers are looking to sunnier times — not just for more sales, but also to power solar cells going on new cars.

Fisker Automotive, a start-up based in Irvine, Calif., goes further. The luxury hybrid shown at last week's North American International Auto Show in Detroit has a large solar panel that supplies extra juice to the battery.

But don't expect to start passing up gas pumps just yet. "Banish any thought that you are really running your car on solar energy," says Bradley Berman, publisher of HybridCars.com. "There simply isn't enough area on the roof of the car that faces and receives the sun's rays hitting it."

Adding a big solar array can stretch mileage 10% at most, says Dan Sherwood, president of 3Prong Power of Berkeley, Calif., which specializes in giving Priuses longer electric-only range.

He considered developing a panel for Priuses, "but it's expensive and people wouldn't like the aesthetics."

Where solar panels are showing up:

•Toyota Prius. The cabin fan is powered by a pair of solar panels embedded in a moonroof. Price of the option is yet to be set, says spokesman Bill Kwong. Also included in the option package for the new Prius, due in late spring, will be a remote-control switch for the air conditioner to cool the car when it's been parked on hot days.

•Fisker Karma. The $87,000 plug-in hybrid, Fisker's first production model, due out later this year, will have a 5-foot-by-4-foot solar panel.

It can add only about 5 all-electric miles a week if the car is parked in the sun all the time, says Fisker's Russell Datz, so the feature is as much about bragging rights as utility. "It fits in with the whole theme of the car," he says. "It's a 'green' car in a market where there are no 'green' cars."