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03132019, 12:19 PM  #1 
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Real world cost & MPG
Few weeks ago I was curious what the real cost of running our i3 and was surprised by the results. Then this week I realized the MPGe rating is nonsense and nothing close to real world MPG. So I ran some numbers and EV's dont provide as much savings as I thought and those Tesla calcs are total bullsh!t.
The problem is any EV savings calcs just use the cost of the kw not all the other related costs on your energy bill. On mine the kw costs about 1213 cents but after supply charges and taxes the total cost per kw is actually 25 cents. I dont know if the whole battery on the Tesla is usable, so I used the total battery on the i3 in the calc versus the actual usable 30kw, if you change it to 30kw it comes out to the same 40mpg as the Model 3. Now if you change the total electricity cost to $0.35 as is found in many major high cost cities, the i3 or Model 3 will not really save you any money over 27 mpg gas equivalent! BMW i3 RexTesla Model 3 LRBMW 330i Battery  kw3375 Electricity Total Cost$0.25$0.25 Battery Charge Cost$8.25$18.75 Range120300 Cost Per Mile$0.069$0.063$0.093 Gas Price Gallon $2.50$2.50 $2.50 Battery  Gas Gallons3.37.5 MPG364027 Cost 12000 Miles$825 $750$1,111
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03142019, 10:05 AM  #2  
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First of all, energy cost varies by location and by your chosen electricity plan (there is more than one to choose from!). There are variable and fixed rate plans, those with fixed usage cost per KWH, and those with variable cost on various thresholds of consumption. To be specific, my cost per KWH is $0.006982 for the first 390 KWH (yes, less than a penny), then $0.102618 for the 1,100 KWH. The delivery charge is $0.035927 per KWH. The overall average for the last NJ JCP&L bill cycle was $0.102618 for energy + $0.035927 for delivery == $0.138545 overall, lets call it $0.14 per KWH. I'm not disputing your observation, just saying that with some shopping, you can probably do better! Quote:
i3 uses 27.2 or 33 KWH battery, or 82% of listed. There is no explicit ratio listed by Tesla, so I would just assume something similar. BTW, premium gas has not been below $3.xx / gallon for a while on the East coast, above $4.xx on the West coast. https://gasprices.aaa.com/ Quote:
I've corrected a few other data inputs in your analysis (see table below), but the bottom line is this: I drive ~300 miles/week in a car. TM3 would cost me almost 1 full battery charge (325 mile range), or $7.95. My BMW M3 costs me 16 gallons of premium, or $48.80. That's 6x difference. Annually, that's the difference between $2,538 (M3) vs. $413 (TM3). To break even between the two, I would need an ICE car with 6x mileage of my M3's daily average mileage of ~19 mpg (more on highway, less on track). That would be a 114 mpg ICE car. I haven't heard of any that approach that. a P.S.: Updated table, formatting likely to be butchered: _______________BMW i3_____Tesla Model 3 LR_____BMW M3_____$ ICE/EV Battery  KW__________33____________75  % usable_____________82%__________82% Battery usable, KW_____27.06__________61.50 Electricity Cost per KW__$0.14__________$0.14 Battery Charge Cost____$3.79__________$8.61 Range_______________114____________325 M3 daily MPG___________________________________18.75 Per gallon cost, premium__________________________$3.05 Cost Per Mile__________$0.0332_____$0.0265________$0.16____ _6.14 Weekly driving_____300_____300_____300 Weekly:____________________$7.95_____$48.80 Annually:___________________$413_____$2,538_____6. 14
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'15 F80 M3 (SO/SS) ex'17 I01 i3BEV (PB/DD), ex'15 I01 i3REX, exE90, E46, E36's, E30's Last edited by afadeev; 03142019 at 10:11 AM.. 

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03152019, 05:36 PM  #4 
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Drives: F80 M3 CS, I01 i3 REx LCI
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That's a lot of math that I'm too lazy right now to check, but all I know is I used to spend $420/mo on gas with my M3. I'm now down to about $140/mo. I've switched to time of day on my power plan and I have not seen a significant increase in my bill at all compared to before I got the i3.
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03172019, 08:48 PM  #5  
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I know there are there, but pretty much a margin of error. In theory, I might see $8 * 4 = $32 in extra charges on an electricity bill that isolates between $50250 throughout the year. In practice, I get free electricity refills at most shopping malls, from BMWGo card (when I bother going to a public charger), and at work. Basically, I might be paying for 1/4 to 1/2 of the estimated max total potential monthly electricity bill. It just too little to bother tracking and quantifying. a
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03222019, 01:48 PM  #6  
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Is the usable battery of both really that low? I thought the i3 had 30 of 33kw usuable.
LOL your electricity is cheap and gas exp. I wish my total kw electricity cost was .13kw and not .25kw. But my gas is $2.60 for 93 and $2.20 for 87. My whole point was that it is different for everyone the cost of an EV vs ICE. Many factors involved, but for some it could be more exp to run an EV than ICE. I tend to question everything in life, analyze it, and do too much research. Surprised it took me so long to figure out my i3 cost, while its worth it because of my wifes long commute and overage miles on the X5, as a stand alone vehicle without the great deal I got, it would not be a good value. Quote:
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03232019, 09:17 PM  #7  
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https://en.wikipedia.org/wiki/BMW_i3 Quote:
We haven't even gotten into the insurance and consumables (tires, pads, rotors, etc) cost comparisons. But that is a discussion for another day. But no, I don't see how per mile cost of EV driving is anywhere within 3x of that of ICE driving. In the case of i3 vs. M3, it's 6x. See my notes above. a
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03252019, 12:22 AM  #8 
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Confusing to me to read your electric costs could possibly rival gas costs. Not even close for me, at around 10 cents kw, I can run about 150 miles on what a gal of gas would cost. Never heard of any EV that wasn't at least a third of the gasser cost per mile.

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04102019, 06:19 PM  #9 
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It's not comparing total apples to oranges but my electric bill went up $8.00 +/ including keeping exterior lights on.
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04222019, 05:38 PM  #10 
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Drives: 2017 i3 REx
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This inspired me to run my own numbers. i3 is easily a 1/3 the cost of money and time for me.
The bigger battery for me wouldn't make much of a difference to me. I plug in at home and it takes so little time I just do it out of habit if I need to or not. Data sources: my charge point charger account http://www.fuelly.com/car/bmw/340i https://www.eia.gov/dnav/pet/hist/Le...te_r50_dpg&f=m 
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