MJ: Prius Envy—When does it make sense to ditch your gas-guzzler for that shiny new hybrid?

[OKIsItJustMe]

http://www.motherjones.com/commentary/columns/2009/01/practical-values-prius-envy.html

Prius Envy

When does it make sense to ditch your gas-guzzler for that shiny new hybrid?

Kimberly Lisagor - February 03, 2009

Thom Davis had a seemingly simple goal: to buy a reliable car while shrinking his carbon footprint. A professor of geology and climatology at Bentley University outside Boston, Davis was looking to replace his beloved 1988 Saab sedan. He found a 1997 model on Craigslist, but it averaged 25 miles per gallon—better than the national average of 22 mpg, but not close to the 30 mpg that the typical new car gets. So he considered splurging on a brand-new, $24,000, 46-mpg Toyota Prius.

Being a science and numbers guy, Davis decided to calculate whether putting a new hybrid on the road really was the greener choice. You might guess the punch line. "My research overwhelmingly indicated that the used Saab would have an overall lower carbon footprint," he reports. Here's why: Davis assumed that he would own his next car for five years and drive it 48,000 miles. Clearly, the Prius won the mileage battle hands down. But once he figured in the energy used to manufacture the hybrid, he found that the '97 Saab required less energy overall—about 14 million btu less, enough to power a fridge for nine years. And less energy, of course, means less carbon.

But wait—it's not as simple as used car good, new Prius bad. Davis' answer would have been different if, say, he planned to keep his next car for 10 years. Or if he planned to drive more. And so on. "It's all a matter of what assumptions you use," says Pablo Päster, the vice president of greenhouse gas management innovations for ClimateCheck, whose data Davis used in his calculations.

Another tricky question is who bears the CO₂ burden of building the car in the first place. "Is the first owner of a new vehicle fully responsible for emissions for manufacturing that car? Or is the company that manufactured it responsible? Or should those emissions be divided out among each year of the car's life?" asks Päster. Davis assumed that he wasn't responsible for the newer used Saab's initial carbon debt since someone else had originally bought it. He gave himself credit for reusing the car—logic that holds up only if buying the used Saab would somehow take a new car off the assembly line. And who was responsible for Davis' old Saab, which would stay on the road unless it was recycled for scrap? (When he does his own calculations, Päster slyly avoids saying who should bear these burdens—leaving the decision of how to split the carbon bill up to you.)

…

[ogneopasno]

1. Very interesting. Thanks for posting.

[madokie]

2. Not

The whole purpose should be to get more of the high mileage autos on our roads as soon as possible. If you own one car then you own the carbon footprint of manufacturing no matter how many different autos you may own and when you own it. Looks to me like that is. I own one auto and so I own one carbon footprint for that vehicle, same as my wife with her auto or you or the next person. HOw else could it be???

If you own one car you own one cars co2 footprint if you own 2 then you own 2 co2 footprints. Wouldn't it be?

[OKIsItJustMe]

3. Look at it this way

Let's say you drive 1 mile a year, in a car that gets one mile to the gallon.^* (See http://en.wikipedia.org/wiki/Reductio_ad_absurdum">Reductio ad absurdum.)

Is it worth it to scrap that old car, and spend all of the energy it will take to manufacture a new car, and ship it to you, so you can drive that one mile a year with the highest efficiency possible? In this extreme case, I think you will agree, it is not.

Now, let's assume you drive 1,000 miles a day, in a car that gets one mile to the gallon. In this case, I will agree that it makes sense to buy a nice new Prius, or some other car to improve your gas mileage.

OK, so, at some point between these two extremes, there is a break-even point. The difficulty lies in determining exactly where that is. There are multiple variables to be considered. (How bad is the mileage? How much do you drive? Will you sell the car to another driver or to the junkyard? …)

… He won't commit to exact numbers, but he does have a rule of thumb: If your jalopy is moderately efficient (i.e., gets better than 25 mpg) and you don't drive it much, keeping it is better than buying a new car. "But if you have an old car with pretty lousy fuel economy," he says, "then you're better off getting a new car because the emissions from making a new car are really not that big compared to the emissions from using the car."

…

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^* (Perhaps it's not that absurd.) When I was a kid, my Grandfather had a Corvair he kept in his barn. When we came to visit, Grandfather would have some errands he wanted to run, but he was too old to drive. So—at Grandfather's insistence—Dad would drive him (a few miles) "in to town" in the Corvair. As a result, that Corvair was only driven a few hundred miles each year.

Though there was no such thing as a Prius in those days, it would have made little ecological sense for Grandfather to have traded in his old Corvair for one.

[Xithras]

4. Well, I can tell you when it DOESN'T

One of my neighbors owns a "green" landscaping company. They use no harmful pesticides, don't use gas powered tools (mostly electric, but some hand tools), and specialize in maintaining sustainable yard spaces (they aren't anti-grass, but they encourage people to devote parts of their property to plants with less impact). Last year, partly to reduce costs and partly for company image, he traded in three Toyota pickups for three bright green Priuses.

Here's where it didn't work out for him. Like all landscaping companies, his employees have to pull around bix enclosed box trailers full of equipment. Between the weight of the trailer, and the weight of the heavy duty receiver and suspension reinforcement he had to put on them, the cars don't even make 20MPG anymore. They rarely run in all-electric mode because the load is simply too much.

Funny thing is, it HAS worked to get him more customers.

[diane in sf]

5. It'll make sense to me when I can get a plug-in hybrid.