Wednesday, December 20, 2006

Buy an SUV, save the world?

I had breakfast with a friend of mine yesterday. It turns out we have both recently purchased hybrids. She moved from a Yukon to a Highlander hybrid. I went from a 3-series BMW to a Prius.

I drove away thinking about our hybrids. She was a bit disappointed with her Highlander's mileage, but it occurred to me that by moving from the Yukon to the Highlander, she reduced carbon emissions by twice the amount that I did by moving from my Beamer to the Prius. These numbers are guesstimates, but let's imagine that we each drive 12,000 miles per year, and that she went from 12 to 24 mpg (actually, I think she's getting more like 28), and I went from 24 to 48 mpg (that's actually pretty close). Those numbers are close enough for illustration, and easy to calculate with. I also found (from here) that 1 gallon of gasoline produces 19.4 pounds of CO2, a pretty amazing number. (Only 5.3 pounds are carbon, the rest is oxygen.)

The Yukon used 1000 gallons a year, producing 19,400 pounds of CO2.
The Highlander (and my Beamer) uses 500 gallons a year, producing 9,700 pounds of CO2.
My Prius uses 250 gallons a year, producing 4,850 pounds of CO2.

So she is saving 9,700 pounds of CO2, while I have only saved 4,850 pounds.

This isn't a trick. It's because the Yukon was using a lot more to start with. But it was illuminating to me. It highlights the disproportionate impact that gas hogs have. And it points out how moving from an inefficient SUV to a more efficient SUV reduces carbon emissions (and fuel consumption) by twice as much relative to the sedan-to-sedan improvement.

Hence the inflammatory title.

Of course, the biggest impact would be to go from Yukon to Prius. But it's interesting how the apparently smaller 12-to-24 change has double the impact of the apparently larger 24-to-48 change. It's all real and explainable, but counter intuitive to a lot of consumers.

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Anonymous Julie said...

This was really interesting to me. My man and I have had several fiery conversations about how creating SUVs that aren't nearly as fuel efficient as, say, a Prius are really GOOD because they get SUV owners, the biggest gas guzzlers, to significantly reduce their emissions and fuel consumption. Still I always find myself contending that many SUV users don't really NEED cars that gargantuan and should just go for what's absolutely most fuel-efficient. Then Josh asks if I'm so devoted, why don't I bike to work. Then I hit him with a rolled-up newspaper, and we continue our day.

In conclusion, I love my hybrid too.

8:37 AM  
Anonymous Julie said...

Darn, I meant to write "creating HYBRID SUVs that aren't nearly...".

8:37 AM  
Blogger Maarten said...

I remember reading about this a while back on the Sightline Daily Score blog. Highly recommended if you care about these issues and related sustainability/environment topics. It's a bit US-Northwest centric, but interesting nontheless.

2:28 PM  

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