It's important to think in terms of the total "well-to-wheels" energy cycle when comparing the emissions and energy usage of vehicles with dissimilar drivetrains.  Start at the oil well or coal mine or wherever you extract primary energy, then follow that energy through all the secondary and tertiary conversions required to get to where the rubber meets the road and a certain amount of cargo and passengers get moved a certain distance in a certain time.  I find it useful to subdivide the total cycle into two stages, well-to-retail and retail-to-wheels, thus considering the part controlled by energy suppliers separately from the part controlled by energy users.

Well-to-retail, modern fossil fuel electricity is about half as efficient as gasoline, meaning that the conventional internal combustion engine vehicle (ICEV) gets a two-to-one head start over the battery electric vehicle (BEV).  But the game turns at the retail sale point.  BEVs using the best modern components are about four times as efficient.  So the worst case is a tie in the well-to-wheels energy race, and the best is about a two-to-one advantage for the BEV.

Emissions Considerations Well-to-wheels emissions are invariably much lower for the BEV, partly because a few thousand power plants are far easier to keep clean than 200 million cars.  Any BEV will be dramatically cleaner than any comparable modern conventional ICEV if the power grid charging the BEV complies with the Clean Air Act.

The BEV is definitely a low emission vehicle, but it's typically also a remote emission vehicle.  The troubling downside is addressing important questions associated with taking broadly dispersed urban and suburban emissions and exporting them to concentrated rural point sources.  It's a lot like making a concerted effort to generate less trash, but then dumping the trash you do generate into your neighbor's yard.  Of course, we could sidestep those questions entirely by installing lots of photovoltaic panels.

Plug-In Hybrid Operation A PHEV works exactly like a BEV during the first portion of any given trip.  Since most trips are fairly short, PHEVs enable their owners to realize the energy and emissions benefits of a BEV for the vast bulk of their driving, while still maintaining an ICEV's ability to make long trips.

Battery Disposal Batteries are made of valuable materials.  In the developed nations, they are also subject to strict environmental laws governing their manufacture and disposal.  As a result, the lead-acid auto battery is the most highly recycled product in the developed world, with recycling rates approaching 100 percent.  For comparison's sake, that's roughly double the rate of aluminum cans.  Unless society takes complete leave of its senses, a shift to newer battery chemistries will not change this highly desirable situation.

Dave Erb started developing hybrids in 1986 as an engineer at a transit bus manufacturer. His second hybrid was a plug-in (PHEV) with 40 miles of pure electric range, built by his students at Weber State University.  They placed second (1993) and first (1994) in a U.S. Dept. of Energy contest called HEV Challenge.  From 1995 to 2004, Dave created and taught a 3-day professional development short course on "Design of Hybrid Electric Vehicles" for the Society of Automotive Engineers. He had been intimately involved in a dozen or so electric and hybrid electric vehicle development projects, and less directly in another 50 or so. He is a former Central Ohio Sierra Club ExCom member, now living in North Carolina. He can be contacted by .