Energy breakpoint - new hybrid vs old car
I've been wondering when the break-even point arrives for a more efficient car when you also count the cost of manufacturing and delivering the car (since for an old car, that is already a sunk cost). Here's the answer.
Re: A Tree in Trade?:
Now let's compare the Prius with an older car. The Prius is rated to get 46 miles per gallon. Let's say your old car gets half as much, or 23 miles per gallon. The average car is now driven about 12,500 miles a year--sad but true, or truly sad. So if you bought a Prius instead of keeping your old car, over that 12,500-mile year you'd save 272 gallons of gas. Since burning a gallon of gas generates 19.5 pounds of carbon dioxide, the Prius would emit 5,300 pounds less CO2 per year than the old car. But because it requires the energy equivalent of about 1,000 gallons of gas to manufacture a Prius--which results in 19,400 pounds of carbon emissions--it would take four years before the Prius started to save that net amount of 5,300 pounds of CO2.
[Now he addresses an earlier question about planting a tree a year instead of getting a hybrid...] In ten years you would have planted ten trees, which together would only absorb about 1,320 pounds of carbon, way less than the almost 32,000 pounds the Prius would've kept out of the air in that period. In the real world, as opposed to the imaginary enchanted forest of Prius haters, it would take 30 or 40 years for the trees to match the Prius's savings on CO2, assuming they all survive--which just might be too long to wait. Seems like we should be buying hybrids and planting trees or, better yet, not driving and planting trees.
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