I heard something similar to this on NPR the other day, and thought it was worth repeating here. Ultimately, I find that the problem relates to people going with their intuition, rather than their desire to do the math (and often, a lack of mathematical ability.) And, unfortunately, "uninformed" public opinion sometimes drives political policy making, which often overlooks more important sides of issues.
This concerns gas mileage: (I remembered this in a furnace efficiency thread where 80% may be cheaper in the long run than 95% efficient)
Suppose a married couple has two vehicles; and each is driven about the same number of miles each year - 12,000 miles. The husband drives (and requires) a truck; and his only gets about 15mpg. The wife has a nice smaller car that gets about 27mpg. The couple decides that they can afford payments on one new vehicle, thus they'll be able to replace only one of the two that they currently own. The choices are to replace the 15mpg truck with a 21mpg truck, or to replace the 27mpg car with a 39mpg car. And, they realize that for just a little bit more money, they might even be able to swing the payments on a 51mpg hybrid, rather than a 39mpg car. What should they do?
Well, most people's intuitions would tell them, "get the hybrid you idiots, that's 23mpg more!" And, while some of you might have done the math in your heads, I'm sure that some of you realize that the hybrid people are wrong, else I wouldn't have written this thread. Thank you for your trust.
Ask this question of most people though, and they'd think it was a no-brainer. You only gain 6mpg with the truck, compared to gaining 12mpg for the car. Or, gaining 23mpg for the hybrid, almost doubling the current mpg!!!
The math: For 12,000 miles, the amount of gas each uses in a year:
15mpg: 800 gallons
21mpg: 571.4 gallons
27mpg: 444.4 gallons
33mpg: (I know, this wasn't an option) 363.6 gallons
39mpg: 307.7 gallons.
45mpg: 266.7 gallons
51mpg: 235.3 gallons
Notice: there isn't a linear relationship between the mpg you gain, and the gallons you save. Going from 15mpg to 21mpg saves 228.6 gallons (This is what upgrading the truck gets you.) Going from 21 to 27 (which wasn't an option) saves only 127 gallons. Going from 27 to 33 saves even less: 76.4 gallons, and 33 to 39 saves only 55.9 gallons. From 39 to 45: 40 gallons, and from 45 to 51: 31.4 gallons.
So, switching from a 15mpg truck to a 21 mpg truck makes much more sense (saves 228.6 gallons) than going from 27mpg to 39mpg (saves 136.7 gallons) And, it still makes more sense than even switching from the 27mpg car to the 51mpg hybrid (which would save 209.1 gallons)
Also worth noting: The difference between a 51mpg hybrid, and a magical 100mpg dream vehicle would "only" save 115.3 gallons of gas a year. That's less gas savings than going from 21mpg to 27mpg. Going from that magical 100mpg vehicle to the absolutely insane 12,000mpg vehicle would save 119 gallons of gas. And, that's even less than the savings in going from 21mpg to 27mpg.
For those of you who drive trucks, large vans, SUV's, etc., (many not because they have a choice of what type of vehicle they own) realize how much of an effect 2 or 3 mpg due to better maintenance can have on your mileage. As a nation, we'd probably save more gas by encouraging the owners of "gas guzzlers" to maintain their vehicles better, than by mandating some arbitrary increase in required average gas mileage by the manufacturers.
This concerns gas mileage: (I remembered this in a furnace efficiency thread where 80% may be cheaper in the long run than 95% efficient)
Suppose a married couple has two vehicles; and each is driven about the same number of miles each year - 12,000 miles. The husband drives (and requires) a truck; and his only gets about 15mpg. The wife has a nice smaller car that gets about 27mpg. The couple decides that they can afford payments on one new vehicle, thus they'll be able to replace only one of the two that they currently own. The choices are to replace the 15mpg truck with a 21mpg truck, or to replace the 27mpg car with a 39mpg car. And, they realize that for just a little bit more money, they might even be able to swing the payments on a 51mpg hybrid, rather than a 39mpg car. What should they do?
Well, most people's intuitions would tell them, "get the hybrid you idiots, that's 23mpg more!" And, while some of you might have done the math in your heads, I'm sure that some of you realize that the hybrid people are wrong, else I wouldn't have written this thread. Thank you for your trust.
Ask this question of most people though, and they'd think it was a no-brainer. You only gain 6mpg with the truck, compared to gaining 12mpg for the car. Or, gaining 23mpg for the hybrid, almost doubling the current mpg!!!
The math: For 12,000 miles, the amount of gas each uses in a year:
15mpg: 800 gallons
21mpg: 571.4 gallons
27mpg: 444.4 gallons
33mpg: (I know, this wasn't an option) 363.6 gallons
39mpg: 307.7 gallons.
45mpg: 266.7 gallons
51mpg: 235.3 gallons
Notice: there isn't a linear relationship between the mpg you gain, and the gallons you save. Going from 15mpg to 21mpg saves 228.6 gallons (This is what upgrading the truck gets you.) Going from 21 to 27 (which wasn't an option) saves only 127 gallons. Going from 27 to 33 saves even less: 76.4 gallons, and 33 to 39 saves only 55.9 gallons. From 39 to 45: 40 gallons, and from 45 to 51: 31.4 gallons.
So, switching from a 15mpg truck to a 21 mpg truck makes much more sense (saves 228.6 gallons) than going from 27mpg to 39mpg (saves 136.7 gallons) And, it still makes more sense than even switching from the 27mpg car to the 51mpg hybrid (which would save 209.1 gallons)
Also worth noting: The difference between a 51mpg hybrid, and a magical 100mpg dream vehicle would "only" save 115.3 gallons of gas a year. That's less gas savings than going from 21mpg to 27mpg. Going from that magical 100mpg vehicle to the absolutely insane 12,000mpg vehicle would save 119 gallons of gas. And, that's even less than the savings in going from 21mpg to 27mpg.
For those of you who drive trucks, large vans, SUV's, etc., (many not because they have a choice of what type of vehicle they own) realize how much of an effect 2 or 3 mpg due to better maintenance can have on your mileage. As a nation, we'd probably save more gas by encouraging the owners of "gas guzzlers" to maintain their vehicles better, than by mandating some arbitrary increase in required average gas mileage by the manufacturers.
).
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