The "Set America Free" Report is based on two well-founded assumptions. One is that the hydrogen economy cannot be realized for at least a couple of decades, a supposition that emerges clearly from recent reports by organizations such as the National Academy of Sciences, in Washington, D.C., and the American Physical Society, based in College Park, Md. Until basic scientific breakthroughs occur, the reports concluded, the hydrogen vision will do nothing to liberate the United States from energy dependence or improve prospects for bringing down greenhouse gas emissions.

The other assumption is that U.S. consumers will be willing, even eager, to pay a premium of a few thousand dollars to get cars that are more fuel efficient and environmentally friendly. Sales of conventional hybrid-electric cars jumped 81 percent in the United States last year and are expected to double this year. These grid-independent (non-plug-in) hybrids cut carbon emissions up to 25 percent and smog precursors by 15 percent. Their gains in fuel efficiency are even more impressive: the Prius gets 4.7 L/100 km (50 mi/gal) on highways, compared with the top-selling Toyota Camry's 7.1 L/100 km (33 mi/gal), and does better yet in stop-and-go traffic, when the battery powers the car more of the time.

But make that car a plug-in, with a battery big enough to keep the vehicle in its electric mode for all daily errands and commuting, and the potential fuel savings become truly prodigious. Researchers have shown that battery packs offering an effective all-electric range of 32 km will yield up to a 50 percent reduction in gasoline consumption. And the hope is that in a few years, when advanced batteries like lithium-ion become cheap enough, there will be plug-ins with an effective electric range approaching 100 km.

At that point, says Mark S. Duvall, manager of technology development for transportation at the utility-sponsored Electric Power Research Institute (EPRI), in Palo Alto, Calif., the car will run on electricity most of the time. Such a vehicle will use only 10 to 15 percent as much liquid fuel as a conventional vehicle.

Duvall points out that there's really not that much difference between the systems in the conventional hybrid cars made by Toyota and Honda, or in Ford's hybrid SUV, and those that would be needed to build a plug-in hybrid. Yet the companies have not made plug-ins available and evidently don't plan to do so anytime soon.

To take Toyota, the leader of the pack: "The corporation is committed to hybrid technology, but so far [only for hybrids that] are grid independent," according to David Hermance, executive engineer at the Toyota Technical Center USA Inc., in Torrance, Calif. Why? Hermance says the answer is simple: the cost of the larger battery packs is so high Toyota could never make a profit selling them at a price consumers would be willing to pay. And that's just one hurdle, says the Toyota engineer.