There are hybrid vehicles, whose gasoline/electric engines get great mileage. And then there are "plug-in" hybrids, only about a dozen of them in the US, which have been modified to store more electricity in beefier batteries by plugging in at night to the electricity grid.
Felix Kramer's "plug-in" Toyota Prius gets about double the mileage of a conventional Prius – about 100 miles per gallon. To him, it is the holy grail of cars, zapping pollution, oil imports, and high pump prices all at once.
So, should the whole country jump on the band wagon?
A groundbreaking study released last week sounds a cautionary note to the consumer. Plug-ins do burn less gasoline than regular hybrids – and gobs less than gasoline-only vehicles – but the high cost of their bigger battery packs will probably neutralize even significant savings at the pump, according to a report by the American Council for an Energy-Efficient America (ACEEE).
The study is the first to compare the performance – and the costs – of two hybrid technologies: the conventional versus the plug-in. It comes even as President Bush, energy-security hawks, and many environmentalists are talking up plug-in hybrid-electric vehicles (PHEVs). Dozens of cities, too, have signed on to promote a new Plug-in Partners program, and Toyota and other automakers say they're working on the technology.
"We want government policy based on reality, not overstating what [plug-in technology] can achieve and when," says report coauthor Therese Langer, ACEEE's transportation program director. "We don't want what happened with the hydrogen hype to happen with plug-in hybrids, too," she adds, referring to optimistic assessments of a timetable for shifting to a hydrogen-powered vehicle fleet.
Environmental impacts of PHEV technology, for instance, would vary dramatically by region – benefiting some areas but not others, the report found.
For a plug-in owner in California, where most electricity on the grid is generated by low-pollution facilities, driving a PHEV might cut emissions of carbon dioxide by one-third compared with driving a regular hybrid.
But if the same PHEV were charged in the Midwest, where coal-fired power plants supply the electricity, reduction of CO2 emissions would be nil. Nitrous-oxide emissions (which form smog) would fall slightly, but sulfur-dioxide emissions (which contribute to acid rain) would quadruple.
Still, environmental gains are possible.
Plug-ins would chop CO2 emissions by 15 percent on a national average, compared with conventional hybrid cars, the ACEEE report found. At the same time, the plug-in would emit 157 percent more sulfur-dioxide pollution. The need, plug-in proponents say, is for policies that would clean up the electricity grid so that PHEV technology supplies cleaner skies along with energy independence.
The cost of nickel-metal hybrid batteries may also limit the appeal of plug-in hybrids – at least in the short run.
Today's conventional hybrids command a premium price – $2,000 to $4,000 more than their nonhybrid counterparts – and their owners will recover that extra cost in about three years, assuming $3-a-gallon gasoline and 12,000 miles a year of driving, the report found.
For the plug-in, the payback period is longer – 6.4 years for a vehicle that can travel 40 miles exclusively on stored electricity – even under the more optimistic scenario in which battery prices fall sharply, the ACEEE report estimates.
Others, however, say that PHEV technology is crucial for America's energy security and that mass production will bring battery prices down.
"This is an important technology from an energy-security standpoint," says Gal Luft, executive director of the Institute for the Analysis of Global Security, a Washington-based energy-security think tank.
Even so, he agrees that expectations have become a bit overheated. "It's true this technology isn't going to be suitable for everyone," he says,
As for Mr. Kramer, who is apparently the first of about a dozen people nationwide to have acquired a plug-in hybrid Toyota Prius, the ACEEE report gives him not a moment's pause. Cofounder of CalCars.org, a group promoting plug-in technology, he keeps close track of his mileage and now commutes to work powered almost solely by stored electricity. On a recent 450-mile run, at mixed speeds and terrain, he got 125 miles to the gallon.
Now he's installed solar panels on his car's roof to charge the battery and lower his costs even further.
"In the real world, battery reliability [will improve] and costs are going to come down fast," he says. "My real-world experience tells me they're understating the benefit. I'm doing a lot better than the report."