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Electric costs compare with petrol...

Discussion in 'Model S: Battery & Charging' started by HumbleDriver, Apr 19, 2017.

  1. HumbleDriver

    HumbleDriver Member

    Joined:
    Dec 28, 2016
    Messages:
    15
    Location:
    USA
    Hi

    I'm not sure there's a question here, but i thought i'd print some calcs i've done regarding electric costs and equivalent petrol costs. I think the numbers are right, but clever folk might see a flaw or two:

    According to my Model S 90D I've done 2863 miles consuming 1198kWh in the process (I've never reset Trip B). This amounts to an average of 418Wh/mile which i put down to cold NE temps and short trips.

    Looking at my last electricity bill - it cost me an average of 16.69c per kWh. So I'd done all of my charging at home, then this means charging my car cost 1198*0.1669=200$.

    Petrol is 2.40$ a gallon now but has been around 2$ when i bought it. Let's call it 2.20$ on average which means I've equivalently consumed around 93.15 gallons (200/2.20), which puts my MpG at 30.7 (2863/93.15).

    This seems like a very poor number. If i'd achieved the magical 300Wh/mile number - this would only be roughly 40% more efficient - giving me an effective Mpg of 42 - better, but hardly setting the world on fire.

    i recall the window sticker for the Tesla giving an MPGe of 103 miles - consumption of 33KWhr per 100 miles - compared with 41Kwhr per 100 for me. This means, the MPGe number must be based on a much lower electricity cost and/or much higher fuel cost. Either way, it's complete nonsense right now.

    So i guess what I'm saying is that with electricity/petrol costs where they are the Model S, relatively speaking, isn't all that efficient right now, and could in fact by quite easily beaten by many ICE models. That's kind of a surprising conclusion to me.

    Thanks (to those that made it this far!)
     
  2. TLej

    TLej Little-Known Member

    Joined:
    Dec 29, 2015
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    149
    Location:
    Edmonton, Alberta, Canada
    I think you're confusing price with efficiency; efficiency is how much energy you've used and has nothing to do with price. Electricity is $0.04/kWh where I live, which is like $0.03/kWh in USD. By your logic, my car would be five times as efficient as yours given the same distance/power consumption, because my electricity costs are 1/5 yours. What you're really saying is your high electricity prices make the relative cost of operating the car much closer to an ICE.

    According to the Google, one gallon of gas is equivalent to 33.4 kWh of electricity, so your useage of 1198 kWh would convert to 35.9 gallons of gas to drive 2863 miles, or 79.75 mpg. Not quite as rated, but much better than your calculation was showing. Nothing to do with a price comparison.

    Hope that makes sense.
     
    • Helpful x 1
  3. HumbleDriver

    HumbleDriver Member

    Joined:
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    Location:
    USA
    Thanks. Congrats on your incredibly cheap electricity by the way.

    I am using efficiency rather loosely above, that is true, but I'm not really confused - the thrust of my post is obviously comparing costs to travel between my car and an ICE car and finding that there was relatively little saving. Clearly, also I've just bought an expensive car and saving money on gas wasn't the point of doing so, it's just me being curious and surprised.

    Even the MpGe window sticker figures quite fuel savings in cash by the way - obviously using price assumptions that are competeoy invalid for my area.

    Thanks.
     
  4. boonedocks

    boonedocks Member

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    Gainesville, GA
    @HumbleDriver this is something that is by far one of the biggest differences based on location. Where I live in GA my kWh rate is $.0649 per kWh for charging in the wee hours of the am. That makes my daily commute of 92 miles $1.947 On the other hand my BMW AH7Li takes almost 4 gallons for the same commute. Also when computing my $ savings I was able to take in to consideration that on my daily commute I drive almost 20 miles in a pay-per-use lane that CAN be as much as $14 each way every day. Averaged out it save me over $260 a month in PeachPass fees. Then take in to consideration that my total electric bill is $275 a month for EVERYTHING and that is for a 13k sqft house with 4 HVAC units and 2 adults and 2 kids. Just the savings in the PeachPass lane is almost paying for my entire electric bill. Be sure you include all possible savings in your computations.
     
    • Like x 1
  5. Brass Guy

    Brass Guy Member

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    Stoughton, MA
    As @TLej stated, the MPGe number reflects energy use, not cost. Just remember that about 80% of the energy output if an ICE is heat, not motion. What a terrible waste of energy, resources and the environment.

    When looking at price comparisons, you always have to look at all the numbers. Tesla's site defaults to $0.12/kWh for electricity, $2.70 for gasoline, and assumes the gasoline vehicle gets 21 MPG. I pay over $0.20/kWh, drove a car that got 30MPG, and used regular gas which is around $2.10 in my area now. If I average 3mi/kWh (after charging losses), that's around $.07/mile; $2.10/gal / (30MPG) = $.07/mile. Pretty much a wash right now, except for the occasional supercharge. Cost per mile was only a small factor in my Tesla decision though, and energy costs are always changing.
     
  6. idealsol

    idealsol Member

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    Location:
    Orange County, Ca
    Like @Brass Guy said, it all depends
    In my case I came from a car that only averaged 20mpg. My rates for electricity are .13 or .14 depending on time of year. I am averaging 353 Wh/M and live in California, where gas is currently ~3.00/gallon. My electric costs are appox 35% of gas.

    So OP still has some possible options
    - lower your Wh/M - maybe easier said than done
    - see if your electric supplier has any options like a TOU plan, etc - we are on SCE and rates are much higher here than some other areas, but our TOU plan helps a lot
     
  7. Blup85

    Blup85 Member

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    Chico
    Last month, I made $10 from my utility company to drive my car rather than my 12mpg Nissan Titan. But of course I've spent 12k on a solar array.. Like @TLeg said, convert it to KW to make an accurate comparison for efficiency. Costs are completely dependent on your geographic location and cost of electricity. My true cost for electricity is 2-4c a KW with my solar..assuming a 25+ year life for the solar array.
     
  8. efusco

    efusco Moderator - Model S & X forums

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    • Informative x 1
  9. HumbleDriver

    HumbleDriver Member

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    Thanks for the responses, for sure I didn't appreciate the significant disparity in electric costs through the country.
    Regarding the survey above - my state is sitting not so pretty at number 50 :(
     
  10. majcina

    majcina Member

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    Feb 23, 2017
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    Location:
    Maryland
    @HumbleDriver Wow! Consider yourself lucky you're breaking evenish if you're in CT. Maybe you should move.

    I'm in Maryland. I've owned the Model S for a month and a half. In my first 30 days of driving it, I'm saving 28% compared to my previous 33 mpg Honda Accord, and that's with a higher electricity rate (because I pay extra to buy all wind power). Obviously, I didn't buy the S to save money. I'm very interested in going green, as you can tell by my signature line below. Also, the Model S is hard to resist after a test drive, even for a guy like me who usually doesn't care about cars.
     

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