Looking at the "marginal electricity mix" – defined as "the mix of power plants that is used to supply the incremental electricity demand from vehicles and fuels" – the study's authors found that even though most of the electricity used to move plug-in vehicles would come from "relatively inefficient steam- and combustion-turbine plants," those plug-in vehicles will still be loads better, carbon-wise, than traditional gasoline vehicles and hybrids.
So, what's the problem? Reading through Green Car Congress' take on the article, we learn that the study found that "All of the pathways except for [fuel cell vehicles] using hydrogen from electrolysis reduce [greenhouse gas] emissions compared to ICEs and [hybrid electric vehicles]." Hydrogen fans can rest easy, though, since the most greenhouse gas emissions are reduced when using either pure electric vehicles "recharging according to the load-level profile" or fuel cell vehicles that use hydrogen made from steam methane reforming.
[Source: Science Direct via Green Car Congress]
Photo by Kenneth Hynek. Licensed under Creative Commons license 2.0.