Monday, April 20, 2009

Saving More Gas than a Prius

Hybrids are popular, hybrids are hip. A Toyota Prius can get an impressive 50 m.p.g., prompting California to give them special driving exemptions: they can use the carpool lane with nothing more than the driver.

But that's not the road to big savings in gasoline.

It sounds like it - 50 mpg is double that of most passenger cars - but the measurement itself is misleading, as you can see from this little quiz:

     Which saves more gas?
  • Replacing a 10 mpg S.U.V. with a 20 mpg station wagon?
  • Replacing a 20 mpg sedan with a 50 mpg hybrid?

Surprise! It's the first option.

The S.U.V. uses 10 gallons to go 100 miles, while the station wagon (and sedan) use 5. The hybrid uses just 2, but that's a smaller savings than replacing the S.U.V.. If you drive a 200 miles a week, moving from the S.U.V. to the station wagon saves you 10 gallons, while moving from the sedan to the hybrid saves you 6 gallons.

It's the low mileage vehicles that add up. Moving from 10 mpg to 20 mpg saves a lot more than from 20 mpg to 40 mpg or even 50 mpg.

This would be easier to see, argue authors Richard Larrick and Jack Soll, if we replaced mpg with "gallons per mile," a measure that better shows the cost and savings of improved efficiency. You can read more about their idea or try a mini-quiz on the topic.

Next week's blog will address Microsoft's newly announced strategy for Windows 7: Microsoft Hobbles Your Fun.

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