@clive I have to agree, the article forgets about net carbon emissions required to produce said mass of 3000lb in the shape of a battery. That takes energy, metal, and producing the metal in the first place. Driving a 1990 Volvo 240 is better for the environment since the overhead of having had to produce it has been spread over 30 years greatly offsetting additional carbon pumped into the air from less fuel efficiency, also who says the hummer battery lasts 30 years?