In the last couple of years, the claim that the Toyota Prius has more environmental impact than a Hummer garnered attention on forums and blogs around the Internet. Hybrid-haters ecstatically point to a study by CNW Marketing Research called "Dust to Dust: The Energy Cost of New Vehicles From Concept to Disposal" (PDF). The premise of this study is that, when taking research, production, and fuel into account, a Prius will use more energy per mile than a Hummer. Knowledgeable people refuted elements of this study, but that didn't stop pundits such as George Will from happily quoting the study.
Now the study has been well discredited in a paper titled "Hummer versus Prius: 'Dust to Dust' Report Misleads the Media and Public with Bad Science" (PDF) by Dr. Peter H. Gleick of the Pacific Institute. Dr. Gleick's paper pokes holes in the original study, pointing out its poor assumptions such as the usable life of a Hummer H1 (35 years) versus the life of a Prius (11) years. The original study also based its conclusions on the lifetime miles of a Prius versus a Hummer H1, where it assumed 109,000 miles versus 379,000 miles, respectively. The 109,000 mile figure for the Prius is truly bizarre, as many people have documented their Priuses getting well over this number.
So the next time someone says, "You know what, a Prius uses more energy than a Hummer," you've got plenty of fuel to tell them they're completely wrong.