"I was a huge skeptic," says Walter McManus, an auto industry researcher at the University of Michigan's Transportation Research Institute in Ann Arbor. "But I've basically crossed over to the dark side. You can't argue with the market reaction." He estimates Toyota, Honda, and others will sell at least 1.2 million hybrid vehicles by 2010 - about 7 percent of the US market - and possibly much higher.
If all US cars (not including light trucks) were Priuses today, the nation would save 15 percent more oil than it received from the Persian Gulf in 2002, writes energy-efficiency guru Amory Lovins in his recent book "Winning the Oil Endgame."
Of course, a sudden switch is virtually impossible, since there are roughly 235 million cars and light trucks on the road in the US today. Less than one-tenth of 1 percent of those - some 200,000 - are hybrids. So the speed of the conversion will determine how much imported oil the nation might save.
"In our view the hybrids represent a long-term trend toward a dramatically more efficient fleet," concluded consulting firm Booz Allen Hamilton in a 2004 report.
For example: If consumers keep snapping up hybrids and automakers begin to integrate the technology throughout their product lines - including pickup trucks - then hybrids might quickly reach 20 percent of new vehicle sales by 2010 and 80 percent by 2015, according to another Booz Allen Hamilton report. That's the most optimistic of three scenarios the management consulting firm laid out. In the "high adoption" scenario, hybrids would save 2 million barrels of gasoline a day by 2015; in the "medium adoption" scenario, 800,000 barrels of gasoline.
Other estimates vary widely. Hybrids could be 10 percent to 15 percent of new vehicle sales by 2012, the Department of Energy's Oak Ridge National Laboratory concluded in a report last summer. Together, hybrids and efficient "clean diesels" could be 40 percent of new car sales by then if the technologies are widely adopted, it said.