Back of the napkin math of last night’s fill-up of 328i vs. cost of ActiveE

After having read yesterday’s post.

One of my cousins asked me how much it would cost to fill up the new car and go 407 miles… (of course going this far would require at LEAST 4-5 charges of the car since the range is 100 miles…  Though, as aggresively as I drive, I’m closer to 80 miles)

Here’s the back of the napkin math. The fill up yesterday was super unleaded at $4.279 per gallon, filled up with 14.022 gallons for a total of $60.00. The range says 407 miles, since I zero out the odometer after each fill up, I know I did 322.6 miles since the last fill up. This is about 1 gallon of gas more than the last fill up (13.077 gallons previously).

So, I figure that my cost per mile (using Super Unleaded) is approx $0.1860 per mile.

On the ActiveE, I’m heavily subsidized… I fill up at many locations where the electricity AND parking is free, the only place it costs to fill up is at home. I do about 35 miles each way to/from work and I charge for free 3/4 of a mile from the office, assuming 10 kWh of energy at home that I fill up and pay for on the average (some fill ups more, some less) to get me to full. Last month I was on the Domestic Tariff for Electricity, which tops off at $0.31 per kWh, so that’s $3.10 per day of fill up, 10kWh is about 1 day in 70 miles roundtrip…

So my electric cost per mile last month is approximately $0.0443 per mile.

So, 407 miles would run $18.03 vs. $60.00 on the 328i… or 1/3rd the cost of a smaller recent 3 series BMW… Numbers look even better versus an X5, but that’s just ridiculous.

The other question he emailed me was to compare it versus a Hybrid. Luckily, I have one of those too. (again, not an environmentalist, it gave me MANY years of carpool access until the privilege was repealed July 1, 2011).  My cost per gallon on my civic right now is $4.109 (educated guess, (not sure what it is right now, haven’t filled up the hybrid since I went electric)) per gallon, 407 miles would probably be 10 gallons (doing average 40-41 mpg), so at $4.109 per gallon That’s $41.09 for 10 gallons and for  407 miles,  that’s $0.1009 per mile, when gas prices go down, the difference between hybrid and electric gets lower and the convenience of gas stations really kicks the butt of having to find EVSE charging stations..

Side note (updated 5/11/12), I have migrated to a Time of Use tariff that drops my cost per kWh to between $0.10 to $0.16 per kWh (depending on Tier 1 or Tier 2 of usage). So, this month’s cost is $0.01412 per mile.

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rEVolutionary armed with a Tesla Model S S85 and a Tesla Roadster, when his wife let's him borrow it. Formerly driving a BMW Active E (2012-Feb to 2014-Feb). Dennis has been driving EVs since he found himself on the BMW Active E trials on February 2012. As a result of his involvement in the Active E program, he became Accidentally Environmental. Aside from this blog, he often tweets @dennis_p. When not driving, he can be found on the following Tesla/EV forums -,, and as AEdennis or on as Dennis. In the interest of full disclosure, Dennis has an inherent bias toward electric vehicles and has an investment in and is LONG Tesla (NASDAQ: TSLA).

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