In response to a comment by an individual interviewed in today's NY Times story that "coal is more polluting than gasoline," we've added a new section at
http://www.calcars.org/vehicles.html (with a link from the excerpt of the Times story)

4. How Much Cleaner than a Gasoline Car is a PHEV Charged from the Dirty (Coal) Grid ?
California, New York, Massachusetts and other states have had Zero-Emission Vehicle Programs since the early 1990s because battery electric vehicles in those states, taking into account power plants, are far cleaner than gasoline cars in reducing urban air pollution and smog. The comparison keeps being raised, though the studies are conclusive.
Studies show that what is called the "well-to-wheel emissions" of electric vehicles are lower than those from gasoline internal combustion vehicles. In California, Air Resources Board studies show that battery electric vehicles emit at least 67% lower "greenhouse gases" than gasoline cars -- even more assuming renewables. A plug-ifPBOV with only 20 miles all-electric daily range is 62% lower: see printed page 95 in the 2004 study,
As for numbers keyed to the national grid, two government studies found plug-in HEVs would result in large reductions even with the national grid (50-60% coal). The GREET 1.6 model in 2001 by the US Department of Energy's Argonne National Lab estimates hybrids reduces greenhouse gases by 22%, and a plug-in hybrid by 36% -- see table 2. An Argonne researcher reached consensus with researchers from other national labs, universities, the Air Resources Board, automakers, utilities and AD Little to estimate in July 2002 that plug-in HEVs using nighttime power reduce greenhouse gases by 46 to 61 percent. Summarized in slide 11 at the November 2003 presentation by EPRI.
Only PHEVs and battery EVs get cleaner as they get older - because the electric grid gets cleaner every decade. Plus more people are installing rooftop solar photovoltaic systems, and clean wind power is vastly expanding nationally (see study by eminent environmentalist Lester Brown cited at CalCars Kudos). Finally, looking at the fuel, not electric component (also of course part of the well-to-wheel totals), instead of using gasoline for long-trips PHEVs could use bio-fuels to further reduce greenhouse gases.
Finally, PHEVs will generally recharge at night from power plants that can't shut down completely -- they don't add to the peak load, and might one day actually help reduce it by providing power from parked PHEVs' batteries during daytime hours (see 7. Vehicle-To-Grid below).