The Prius's mediocre cost-per-mile is due mainly to CNW Research assigning the car a short expected lifetime: 109,000 miles. Nobody knows where this number comes from because CNW has not published details about its derivation. If a car will not last very long, then of course its energy cost per mile is high.
Back in July 2006, when CNW's study "Dust to Dust" had just been published (and which remains, unchanged, the original source for today's news), I emailed its president, Art Spinella:
I'm with the tech news and discussion site Slashdot.org. One of our readers submitted a story about your Dust to Dust study.
According to Wikipedia, the Prius comes with a 150,000 mile warranty in California and a few other states; 100,000 elsewhere.
On p. 21 and p. 40 of your report I see that you estimate the average Prius will be "removed from the streets... and sent for disposal" at 109,000 miles. Can you explain how you arrived at this figure?
I did not receive a reply.
My question was about the cost-per-mile denominator; here's another critique questioning the numerator.