Carnegie Mellon University’s Jeremy J. Michalek and co-authors report that plug-in vehicles with small battery packs and hybrid electric vehicles (HEVs) that don’t plug in can reduce life cycle impacts from air emissions and enhance oil security at low or no additional cost over a lifetime. But plug-in vehicles with large battery packs are more costly and may have higher or lower emissions than HEVs depending on where and when they are plugged in.
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