Spilled watts

If I draw 10 gallons of Shell V-Power out of the pump, I’m getting, give or take a tablespoon or two, 10 gallons; the Corporation Commission sees to that. After that, the laws of physics kick in, and internal-combustion engines are not exactly celebrated for their efficiency, which is one reason why electric-powered cars are selling in quantities no longer describable as miniscule.

Then again, if you draw 100 kilowatt-hours out of the line, how much of that is the car going to use? Here’s what one Tesla Model S owner found, after installing a digital submeter to determine exactly how much juice is leaving the outlet and going into the car:

[T]he Model S reported 728 kWh used during the period but the meter reported 894 kWh used. This means my charging efficiency is only about 82% and electric usage (and cost) is 18% higher than I may have expected based on the readings the Model S provides. For that month this is an extra $26 of charging cost which is a small number but a notable percentage of the total.

At his, um, current (sorry) electrical rate, he wound up using $143 worth of electricity for that month — to drive 2,417 miles. At my around-town figure of 21.5 mpg, this means I’d be buying 112.4 gallons of gas to drive that same distance, and at last weekend’s fillup price ($3.299), I’m looking at $370 in fuel costs. So even if Tesla doesn’t win by as much as he’d hoped — some electrics, he says, manage 90-percent charging efficiency — it’s still a pretty substantial win.

(Via Autoblog Green.)


  1. stixx23 »

    5 August 2014 · 1:28 pm

    I usually get over 35mpge with my Honda Civic CNG, but using 33 in the scenario above and $1.39/ge as the fuel cost (7-11 in Moore has that price), I spend $101.81.

    Granted, I commute between Norman and OKC every day, giving me the higher efficiency.

  2. jsallison »

    7 August 2014 · 7:28 pm

    Hour and a half-ish to go the 86 miles from Lawton to OKC. Show me something electric that’ll hold up to that 172 mile round trip 5 days/wk.lk I’d go the CNG route if I could find something bigger than a skateboard…err, Civic. Better yet, I’d pay 200-250/mo to commute by rail but that’s pretty much a pipe dream.

  3. CGHill »

    7 August 2014 · 8:29 pm

    This fall, we are told, there will be a pilot program running two trains a day between Midwest City and Sapulpa, operated by the Stillwater Central Railroad, which bought an existing freight line from OTC. That’s about 86 miles, but it’s $30ish round trip, not bad for a daytripper but horrid for a commuter.

    (Details at passengerrailok.org.)

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