Friday, August 31, 2007

Buying a Prius vs. keeping the old car

I've spontaneously had the "buy new Prius vs. keep old car" discussion with a number of different friends now, so I decided to gather a bit of information on it. The question I'm mainly concerned with is whether the energy savings of driving a Prius outweighs the energy cost of manufacturing it.

The "Hey Mr. Green" advice column and mailbag from Sierra magazine claim that the energy required to manufacture a new car is equivalent to 1000 gallons of gasoline and that a Prius recoups its energy outlay in about 50K miles, but the author doesn't cite much in the way of sources.

An advice column from Wired says essentially the same thing as Sierra. The Wired author also makes the case that buying a hybrid supports the growth of clean tech, and helps build the perception of hybrids as a mainstream car (as opposed to an elite treehugger yuppie car :)

I admit I didn't spend much time googling, but I was a bit disappointed not to find a more detailed lifecycle analysis of the Prius and its manufacturing costs. However, I did find a high-level comparative lifecycle analysis of the Prius published by the Rocky Mountain Institute as a rebuttal to the controversial CNW study that claimed that a Prius has a greater environmental cost than a Hummer.

According to the EPA, a 2007 Prius gets 46 mpg and my 1999 Civic with 58K miles on it gets 27 mpg. Assuming that the energy cost of manufacturing the Prius is indeed equivalent to 1000 gallons of gasoline, I calculated that at my current rate of driving, it would take nine years for me to recoup the energy costs of a new Prius. Moreover, in the last 5 months I have been averaging about 180 miles a month. This glacial pace of driving is not going to last forever, but if it did, it would take 30 years to recoup the costs! As Mr. Green from Sierra magazine says, "If you don't drive much, it may be better to keep the old car". I think this speaks volumes about "just driving less" as being the ultimate fuel efficiency strategy.


Anonymous said...

Hey the Mander,
what about looking into a scooter? I hear they go up to 40 mph and you get approx 100 miles to the tank. I haven't looked into it completely, but it may be a viable route for traveling much farther distances than on foot, but without the hassle of a vehicle. I know nothing about it's emmissions though.

Blue Yonder said...

A scooter sounds like a great option. Since it weighs so much less than a car, the energy required for its manufacture is probably significantly less. And since carbon dioxide output is directly proportional to mileage, it sounds like solo driving on a scooter beats solo driving in a Prius! Right now, though, the subject is an academic one for me, since I'm not in the market for a new vehicle yet...I just like to discuss this kind of stuff with friends :)