http://www.emagazine.com/­earthtalk/­archives.php?current E/The Environment Magazine EARTHTALK: Questions and Answers About Our Environment Week of 3/05/2006

Dear EarthTalk: As I understand it, "hybrid" cars make use of an electric motor that never needs to be plugged in. But what's up with the proposed "plug-in" hybrids I've been hearing about? -- Jen Seminara, Omaha, NE

The mass-market gasoline-electric hybrids made by Toyota, Honda and others make use of an electric engine right under the hood next to the gas engine. That electric motor creates fuel economy by kicking into use during idling, backing up, slow traffic, and to maintain speed after the gas engine has been employed for acceleration. The car doesn't need to be plugged in because the on-board electric battery is constantly being charged by the gas engine and by the motion of the wheels and the brakes.

The so-called "plug-in hybrids," now in prototype stages of development, take this technology a step further. By adding the ability to charge up from a standard household outlet, typically overnight, such cars relegate the gas engine to back-up status and instead let the electric motor do most of the work.

Proponents claim that such "gas-optional" cars--if you don't take long trips you can rely entirely on the electric motor--can be twice as fuel efficient as hybrids, which already get double the gas mileage of traditional vehicles. Additionally, they say, powering up plug-in hybrids with wall sockets results in far less pollution (from the power plants providing the electricity) than an equivalent gasoline-powered car spews out its tailpipe. Meanwhile, plug-in hybrids recharged from rooftop solar power systems might approach being the world's first mass-market "zero emission" vehicles, requiring no power from the grid at all.

Convincing a skeptical American public that plug-in hybrids are the way of the future is the challenge of a loose network of advocacy groups led by the California Cars Initiative (CalCars). Indeed, the experimental electric vehicles of a decade ago and older required re-charging every 25-50 miles, rendering them useless for anything but short trips. The new breed of plug-in hybrids solves this problem by employing much more sophisticated battery technology while still keeping the insurance of gasoline (and a gas engine) on-board.

"It's like having a second small fuel tank that you always use first--only you fill this tank at home with electricity at an equivalent cost of under $1/gallon," reports the CalCars website. The organization goes on to explain that with gas prices at $3/gallon, traditional cars cost eight to 20 cents per mile, while plug-in hybrids used for all-electric local travel and commuting would cost only two to four cents per mile.

CalCars is lobbying the world's major automakers to introduce plug-in options on future hybrid models, and has built showcase examples themselves that achieve 100 miles per gallon using Toyota's Prius. Meanwhile, a growing list of state and local governments say they would seriously consider converting their fleets to plug-in hybrids if such vehicles became available.

The website HybridCars.com reports that DaimlerChrysler has built a handful of prototypes based on its 15-passenger Mercedes-Benz Sprinter van. And analysts believe Toyota already has the technology in place but may be waiting to gauge consumer demand before making any production commitments. Only time--with a little guidance from the price of gasoline--will tell.

CONTACT: California Cars Initiative (CalCars), http://www.calcars.org.