calculating gas savings

Discussion in 'Gen 2 Prius Main Forum' started by finman, Nov 5, 2004.

  1. finman

    finman Senior Member

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    So I've hit the 15K mile mark and decided to calculate my gas savings over the past 8 months (yes, I just LOVE to drive this car!). 15,500 miles using 330 gallons of gas (46 MPG) X $2.00/gal = $660.
    Seems kinda high until I compare to my old vehicle, a 1989 Nissan Pathfinder. I will admit I didn't track mileage as closely as my Prius but 15 MPG is a fair guesstimate.
    15500 miles at 15 MPG = 1,033 gallons. That's about a 700 gallon savings, which = $1400.
    Your results may vary, but I for one see my 'investment' being justified in another 15K miles (roughly $2800 saved in gas). That should occur within 2 years of purchasing my Prius, well ahead of the 10 year time frame claimed by 'experts'. I use the $2800 figure with all the 'experts' claiming hybrids cost $3000 more than a comparable gas-only car, even though the Prius has no equal when you factor in the tech, the extras, the roominess, the fun-to-drive-factor, and lest not forget the partial zero emissions! Nice! I can't wait for the next 15,000 miles.
     
  2. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I used to track my '98 Buick Regal. Every week I put about 11 gallons in the tank. At $2.00 per gallon, that's (11 x 52 x $2.00) = $1,144.

    I had a 22.5 MPG average over the summer from Feb. to Aug. (while I was waiting for Priapus). I can only assume the mileage would be worse in the winter, but won't go ino that much detail. I will simply say that at 22.5 MPG, every tank gave me around (22.5 x 11) = 247 miles. In one year, that's an average of (247 x 52) = 12,844 miles per year.

    Priapus is currently giving me an average of 47.5 MPG. To drive the same 12,844 miles, I will have to use around (12,844 / 47.5 ) = 270.4 gallons. At the same $2.00 per gallon, that's around $541.

    A savings of ($1,144 - $541) = $482.
     
  3. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    Tony...

    how come you don t use a calculator?
     
  4. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    Dammit, Dave!
    Is my math all screwed up? I was using a calcualtor and referencing my old records at the same time. I might have crossed realized experience with calcualted results. Now I have to redo everything.
     
  5. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    well Tony...

    i didnt use a calculator but when going from a car (22.5 mpg) that gets less than half the mileage of your Prius (47.5) then the savings will be more than double the amount of gas spent in the Prius correct?

    well that is not what you have reflected when you stated the Prius uses $541 and saved $482.

    personally i think the numbers ultimately will be correct simply because the Prius is a much more pleasant driving experience which in turn result in more miles driven in the Prius than with your other vehicle making the savings about right.
     
  6. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    First of all, I have a degree in Language and Linguistics, not Math. Ok, also one in Computer Science, but that's different! :)

    I'm stumped. I must really be looking at this whole problem from the wrong angle. I've recrunched the numbers but keep coming up with the same results. I've tried a few other approaches, but haven't gotten anything to work out.

    From now on I'm just going to say that I get more than twice as much in MPG so I pay less than half in gas.
    My brain's shot; I need coffee. :goodmorning:
     
  7. bruceha_2000

    bruceha_2000 Senior Member

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    We'll give you this one Tony, but you have to earn the next one. Remember, ALWAYS check your answer to see if it is reasonable. If it isn't, start over. At least that is what we tell the girls regarding their math. :)

    I don't know how you did it, I can't even get close by transposing the digits in the numbers, but the answer is: $1144-$541 = $603

    Let's see, is it reasonable? We expect the amount saved to be more than the amount spent on gas for the Prius since it gets better than twice the mileage. Yep, it is reasonable. :)
     
  8. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    hmmm... i still think that he will enjoy driving the Prius so much more that he will only save $482 like he said.
     
  9. bruceha_2000

    bruceha_2000 Senior Member

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    Hmmm, a new article: The REAL reason people don't think the Prius gets the mileage they expect

    "Prius drivers so enjoy their cars they are spending almost as much on gas as they did when they drove an SUV. In fact, most drive at least 3 times as many miles in their Prius. Thus, while they expected to fill up only once or twice a month, they have to get gas nearly as often. "

    :D
     
  10. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I realize that we've gone in a direction other than that in which finman had in mind. And here I thought I was adding to the conversation when it seems I only mucked it up. And Bruce, I'm not sure how I did it either, but I SWEAR that's the number I got a couple times over. Oh well.

    Though this has gotten me thinking. Someone mentioned that there's a savings calculator either on the Prius site or on the Ford Escape or Accord Hybrid site. I will try to whip something up for the Files section of PriusChat. An Excel spreadsheet that will allow the user to enter their current car's MPG and show gallons and dollars savings per year.

    I think what finman started will turn into something everyone can use to calculate savings already realized - as in his case - or potential savings for those considering or waiting.

    But of course, if someone who is better at math than I would want to do this, be my guest. I've already proven my skills. :?
     
  11. kjb516

    kjb516 New Member

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    I recently reviewed the EPA mpg for every car I’ve ever owned versus the average yearly gasoline price for the entire 22 years I’ve had a license. As I’ve usually been able to achieve nearly the EPA ratings in each car (yes, even in my Prius), I used this number to calculate my average pennies per mile fuel cost since 1982.

    To my shock and delight, I realized that I haven’t driven this cheaply since 1986 when I was driving a Chevrolet Chevette (~28 mpg) and gasoline, according to the California Energy Commission web site, was around 87.4 cents per gallon.
     
  12. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    Bruceha_2000

    i can agree with that. before driving was a hassle and i avoided it a lot without realizing it.

    now, i find that i am willing to drive farther and more often.

    last weekend for a family birthday, i carted my sister and two kids to my sister-in-laws house. normally, i would have probably driven myself, been late, broke all laws getting there, etc.

    now i look forward to it for reasons i am not sure of. the newness of the Prius has worn off (i think) and since my car was a basic model, there isnt nearly as much to play with.

    i guess it could be another attempt at showing off the car to someone, but the people in question have seen and ridden in my car several times.

    my niece is a 14 year old who like all other 14 year olds constantly needs rides. i now know all her friends and no longer needs directions to nearly anywhere she has to go. because two of her friends live near me, she now calls me first before calling mom and dad, and both are VERY happy about that. (realize both constantly complain about the price of gas while i mention that i dont get gas often enough to remember what i paid for it the last time i filled up)
     
  13. Prius Maximus

    Prius Maximus Senior Member

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    I thought I was going to be clever and update my MPG spreadsheet to figure my cost savings over my old car. I came here to brag but you all beat me to it.

    Anyway, my old car was a Dodge Neon which got a lifetime average of 27.8 mpg. I am at 50.9 for the Prius lifetime. Since delivery of the Prius in March '04, I figure I have saved $640.

    I see there is some confusion over how to figure savings. Here is what I did:

    I took the elapsed miles for the current Prius tank fillup and divided it by the Neon lifetime average MPG to get the gallons the Neon would have used. Then I multiplied that answer by the current price per gallon to get the total cost of a fillup for the Neon. That number minus the total cost of the current Prius fillup gives the savings for the tank. A simple summation calculates the total savings. I uploaded a simple spreadsheet into the file library that calculates money saved.

    (I have columns in my spreadsheet for total miles, elapsed miles, elapsed gallons, calculated MPG, cost, price per gallon, date, display MPG, and display/calculated mpg difference. Most of these columns have a heading that shows the maximum, minimum and average over all entries.)
     
  14. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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  15. karmavore

    karmavore New Member

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    <div class='quotetop'>QUOTE(finman\";p=\"48729)</div>
    I've been doing the same, tracking my gas savings. Sadly, I don't drive enough to get to "break-even" so quickly. (So I wind up concentrating on the fun-to-drive and fun-to-own and fun-to-think-about factor. Poor me. :) )

    Nevertheless, I feel obligated to point out a major flaw, not in the mathematics, but rather in the reasoning: the 'experts' are comparing MPG in the Prius to MPG in a 'comparable' new automobile. It's not (I'll just say) "fair" to compare your number, using an 89 Pathfinder (or my number, with a 92 Olds Ciera) to the 'experts' number, using an 04 Corolla.

    If you really want to do a valid comparison to your Pathfinder, you'll need to recover, in gasoline, the entire cost of the Prius minus the cost of anticipated repairs on the 89 Nissan.

    We get so frustrated when publications misrepresent the capabilities of Prius; we've got to be careful not to fall into the same traps on the other side. :)

    Cheers,
    Brad

    p.s. Yeah, I know: what is "comparable" to a Prius?

    p.p.s. What could a Prius get in MPG if there were no battery? Hmm...
     
  16. finman

    finman Senior Member

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    Ya know, I realized that mistake shortly after posting my calculations. Yes, it's true. Must compare apples to apples, etc. I just wanted to show that conserving gas is good and doable. Lots of other factors I didn't figure should be considered, as always. I was really blown away with the gallons saved figure (700 gallons). That right there told me I did the right thing. Less polution, less foreign oil going into my tank.

    I wanted to keep it simple for my sake when doing the comparison. I did not have a car payment with my old truck, had lower insurance to pay. I rode my Harley more ('cause it was more fun). Now I think the Prius is more fun, (sorry Harley riders!). It has a better stereo and heater. I definitely believe the Prius is in a class by itself...
     
  17. kjb516

    kjb516 New Member

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    Another reasoning flaw I've found with breakeven calculations, is the wrongful assumption made by many that use current gasoline prices to calculate future savings.

    Having detailed records of my fuel purchases over the last three years, a simple graph of gasoline prices over time with a linear trend line into the future indicate a price in excess of $3.50 a gallon by July 2011 (my current expectations for keeping my Prius). Personally, I believe that a linear trend is too optimistic and the price will more than likely be around the $5.00 / gallon exponential trend line predication.
     
  18. karmavore

    karmavore New Member

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    While no one can dispute that gasoline prices will go up, the price increases we've experienced throught the last 20 years have been almost completely due to inflation. Since we're not adjusting future dollars for inflation, using today's gasoline prices certainly seems reasonable. (Using three years of history to project out seven years certainly does not.)

    See this chart of Gasoline Price History for evidence of what I'm referring to.

    I don't mean to start a debate on Hubbard's Curve, oil, and the like. I do believe gasoline prices will increase, relative to inflation, above the level of the '80s. I only assert that we don't know exactly when this will happen, though it's a good bet that the bulk comes after current owners have already hit break-even, and therefore not necessary to include in this calculation.

    Brad
     
  19. ssmithri

    ssmithri New Member

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    Greetings... I am a newbie to this site and a new Pirus owner.

    I do not know all of the intricacies regarding mileage calculations, etc..., but I do know one thing. By the time I will have to fill up my Prius for the frist time (around $20.00-the dealer gave me the first tank), I would have had to fill up my SUV five times ($60.00).

    Calculate it any way you want. This is cash in my pocket.

    :mrgreen:
     
  20. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    Leave it to the "newbie" to keep things in perspective. I admit that sometimes we over-analyse things a little too much. I started working in the "oil change every 3,000 vs. 5,000" as well as the estimated repair costs but figured my time would be better spent doing anything else.

    Welcome to PriusChat, ssmithri! I hope you find a lot of good information here and stick around a long time.
     
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