Are electric vehicles really better for the planet?

Some time ago I read a careful analysis of the energy required to manufacture a Toyota Prius, which reported that more energy was expended over the life cycle of the typical vehicle (manufacturing the batteries being very energy intensive) than by a high efficiency gasoline-burning cars. I then lost the reference, and so was pleased to come upon the report below in Science Magazine by Wigginton. Work like this makes me feel a bit less guilty about staying with my cheap Honda Civic, and more able to resist the subtle aura of superiority that I imagine is being emitted by friends smugly driving about in their Toyota Priuses:

Shifting to electric passenger vehicles ideally will reduce the carbon footprint of the transportation sector. Two recent studies, however, show that the greenhouse gas emissions produced over the life cycle of electric vehicles, from production through use, may not always be less than those of gasoline-burning vehicles. Ellingsen et al. reveal that vehicle and battery size prohibit some larger electric vehicles from ever overcoming the high greenhouse gas emissions generated during production. Yuksel et al. show that regional factors in the United States such as electrical grid mix, temperature, and driving conditions strongly limit the potential of plug-in electric vehicles to out-perform high-efficiency gas vehicles. Blanket policies directed at the adoption of electric vehicles therefore could potentially fail to reduce the transportation sector's large carbon footprint.