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Winter, Spring, Summer or Fall - MPGe in environments with extremes

Discussion in 'Model S: Battery & Charging' started by pbleic, Feb 6, 2014.

  1. pbleic

    pbleic Member

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    I am trying to figure out the practicality of the Tesla in my life as our primary car for roadtrips, etc. I know that the MPGe by the EPA is 89 (yes, YMpgMV), but I am wondering about MPGe in hot and cold environments.

    What should I expect in the summer, with AC on much of the time? What can I expect in the winter with heater on all the time? What would someone guess is an average MPGe for a car in Boston, which has hot summers and cold winters?
     
  2. mnx

    mnx 2013 P85

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    You might find this thread useful. Lifetime Average Wh/mi

    Owners report their lifetime average Wh/mi, it's tabulated and averaged out over location etc. It's up to you to convert it to mpge though. :)

    edit: there are 2 owners in MA who have reported an average of 364Wh/mi.
     
  3. zwede

    zwede 2013 P85+

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    My driving is pretty much worst case, only short distances and 4 "cold starts" in a day. I'm losing about 40% range, meaning when I get home I'm down 40 miles but have only traveled a bit over 20. It's so bad as my battery heater runs and then just when it gets up to temp, I'm at my destination. Temps have been around freezing here. My trip economy has been in the high 300's sometimes, but usually is in the 400's.

    The further you go, the smaller the "cold start penalty" becomes. Bjorn over in Norway reports a 20% loss, but he's driving further each trip.
     
  4. Zythryn

    Zythryn MS 70D, MX 90D

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    There are a lot of details that go into the calculation.
    What are the specifics of the car you're looking at, are you going to be using 19 inch or 21 inch tires, 60kWh, 85kWh, or performance?
    As I recall the EPA numbers are based on 308 Wh per mile.
    In MN (with winters that get very cold), I average about 390 Wh/mile in the winter and 290 in the spring, summer and fall.
    AC has a much smaller impact on efficiency than heat.

    Charging efficiency also plays a lesser role.

    Instead of MPGe, you may want to look at cents per mile. It is simpler and more direct. However it does depend on your local electricity costs. For us, spring, summer and fall costs us about 2.5 cents per mile. Gas in another large sedan (24 mpg) runs about 13 cents per mile. In the winter it is about 4 cents per mile vs 15.6 cents per mile.
     
  5. pbleic

    pbleic Member

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    19 inch, 85kWh. Thanks.
     
  6. Zythryn

    Zythryn MS 70D, MX 90D

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    The 19 inch tire generally get better Wh/mile than the 21.
    Our 1 year average was 332Wh/mile in MN. In Boston I would expect you could do better, but it largely depends on your driving behavior and patterns.
     
  7. donv

    donv Member

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    There is another factor which is that electricity is usually much cheaper than gasoline for a given amount of energy. So even if your energy use were the same (and it won't be), you'll end up spending less money.

    That said, owning a Model S isn't about saving money, let's be honest here.
     
  8. Zythryn

    Zythryn MS 70D, MX 90D

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    Very good point (the first one). As an example, if I had an average 24mpg car it would cost me $3.10 to go 24 miles. Right now it costs me about 70 cents to go that distance in my Model S and about 45 cents in the summer.

    As to your second point, I know of a number of drivers where the additional savings on fuel allow them to stretch and buy the S when normally they never would.
     
  9. pbleic

    pbleic Member

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    Exactly right. I am thinking that the $2,000 saved per year (my estimate on ~12,000 miles driving per year) will lead to a $12,000 savings during the life of the car. And hopefully, reduced regular maintenance costs. Even for those who don't have to stretch, it reduces the extra cost you have to rationalize to yourself.
     

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