Unfortunately for his checkbook and the Arizona air, he figured incorrectly.

"It doesn't make any sense," says DeCock, a 30-year-old software tester in Tempe. "These incentives seem to be based on the emission rating, but here's a car that has an extremely low emission rating and it didn't qualify. It's extremely frustrating."

What gives? Why is the federal government unwilling to offer incentives for environmentally friendly hybrids like the Prius or the Honda Insight? And why aren't states like Arizona and California eagerly subsidizing these ecofriendly cars as they're doing for other options, like Ford F-150 trucks that run on propane?

The Department of Energy's Office of Transportation Technologies Web page offers an answer, stating that "because the [hybrid vehicles] on the market today do not use alternative fuels (they use gasoline), they can't be considered for credits" under Energy Policy Act.

And Richard Varenchik, spokesman for the California Air Resources Board, the state agency that regulates emissions, says that hybrids don't deserve special treatment because gasoline is simply a dirtier fuel than alternatives such as propane. So even hybrid advances like bladder gas tanks -- which contract and expand according to the fuel level, thus decreasing evaporative fumes that are precursors to ozone -- don't do much good. Plus, because of gasoline's more complex chemical makeup, it will soil everything it touches.

"A gasoline-powered vehicle will suffer some degradation," he explains. "It won't be as clean at 40,000 miles as it was at 4,000, which is why anything that has a gasoline engine can't be as clean as one that doesn't."

But experts insist that energy departments are dodging the issue, focusing more on politics and legal technicalities than on the environment. By accepting the "alternative fuels" language of the law, they're eyeing what goes into a car at the expense of what comes out. And in the process, they're perpetuating a system that hampers the rise of ecofriendly cars and essentially punishes consumers like DeCock who would like to help, but don't want to spend over $20,000 for what is essentially a low-budget compact.

"There are no compelling reasons not to make these cars eligible," says Dan Kammen, professor of energy and society at the University of California at Berkeley. "It's ridiculous. These hybrid vehicles are significantly cleaner and they should be supported."

In fact, they represent the dominant innovation for the next decade in terms of fuel efficiency and pollution reduction, says David Nemtzow, president of the Alliance to Save Energy, a Washington nonprofit that lobbies for energy efficiency. Zero-emission options like cars that run solely on electricity are years away from being viable, and the infrastructure isn't in place. That's why only a fraction of the cars on the road -- 2,000 out of millions in California, for example -- run on alternative fuels.

"You simply can't recharge a battery as easily as you can fill a tank with gas," he says. "That's why hybrids are so vital. You can just fill them up, which is to say that their weakness is their greatest strength. They make for a perfect transition."

And if laws aren't rewritten to subsidize them, the country faces two big risks: "One is that hybrids will not catch on quickly. Therefore, we'll be wasting gas and creating pollution that's completely unnecessary," he says.

"The second risk is that we'll relive the '70s, which is to say that Toyota and Honda will outpace the domestic car companies." In other words, when the public -- perhaps disgusted with pump prices of $3 per gallon -- gives up once again on gas hogs, Japanese carmakers will be the ones that benefit.

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