www.slate.com/id/2194989
com >> the green lantern: Illuminating answers to environmental questions. Green BeatersIs it more energy-efficient to buy a gas-guzzling used car than a brand-new hybrid?
I'm shopping for a car, and my tree-hugging pals are pushing me to get a Prius. But it seems wasteful to buy a brand-new car, given all the energy that goes into the production process. Wouldn't it be greener to get a certified, pre-owned vehicle with decent gas mileage?
Click image to expand A Toyota Prius Your query is a serious toughie, as we don't really know how much energy it takes to manufacture a hybrid. Toyota does admit that because the Prius' engine and battery are relatively complex, assembling the hybrid requires more energy than making a similarly sized nonhybrid vehicle. But the company has never quantified that energy premium, so the Lantern will have to rely on an educated guess. If our informed figure is in the ballpark, however, a fresh Prius beats virtually all used competitors--assuming you follow the Lantern's golden rule and keep your car running until the bitter end.
Beyond 172,500 miles, then, the Prius will consume 3,710 gallons of gas. Each gallon contains approximately 124,000 BTUs of energy, so that translates into 460 million BTUs' worth of burned fuel. Add in the production energy, and the new Prius is responsible for a grand total of 573 million BTUs over its lifetime (not including disposal costs). Over the vehicle's lifetime, that translates into 5,656 gallons of gas containing more than 701 million BTUs of energy. Since the Corolla we're considering is used, we won't add to that total by factoring in production energy.
In fact, a certified, pre-owned car would have to average better than 37 mpg in order to match the Prius' energy consumption over the long haul. And the only nonhybrid cars to achieve such lofty fuel-economy heights are either tiny or diesel-powered.
There are complications to this comparison, of course, beginning with the uncertainty over the figure for the Prius' production energy--it may not take into account certain inefficiencies in Toyota's assembly-line equipment. There are also various wild cards to consider, like whether the Prius' complicated battery would need to be replaced, whether the used Corolla would become less fuel-efficient at an earlier age because of wear, and how driver habits affect fuel economy. The scales could definitely tip in favor of the used Corolla if you put the $5,000 you saved toward making some critical technological upgrades in your house--for example, converting to an EnergyStar water heater or dishwasher (though, granted, with gasoline at $4 per gallon, the Corolla in our comparison would end up costing you an extra $7,700 in fuel costs over 172,500 miles). Here's the bottom line: The Prius is by no means a perfect car, but it's certainly tough to beat in terms of cradle-to-grave, pound-for-pound energy consumption. Is there an environmental quandary that's been keeping you up at night?
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