Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Tesla Motors claims 114% efficiency

  1. Jul 19, 2008 #1
    Tesla Motors claims a "well-to-wheel" efficiency of 1.14

    http://www.teslamotors.com/efficiency/well_to_wheel.php" [Broken]

    What in the blue blazes are they talking about?
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Jul 19, 2008 #2


    Staff: Mentor

    Look at the units. That is 1.14 km/MJ efficiency, not 114% efficiency.
  4. Jul 19, 2008 #3

    Ivan Seeking

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    They certainly aren't including the cradle to grave energy costs.

    How much energy does it take to make 900 Lbs of Li ion batteries, and how are they recycled.
    Last edited: Jul 19, 2008
  5. Jul 19, 2008 #4
    The energy cost of production of the system isn't part of the system efficiency calculation, it never is.
    The well to wheel efficiency is a measure of how much of the available energy contained in whatever raw material used for fuel actually makes it to the driving wheels of the car.

    ... and Tesla published a blog about receycling of the Li-Ion cells: http://www.teslamotors.com/blog4/?p=66
  6. Jul 19, 2008 #5
    Thanks, DaleSpam. Blind spots, you know.

    Something else is a bit odd. They quote a "Source Fuel" of natural gas, while 49-51% of US electricity is generated with coal. However, they are located on the west coast, in California with electricity generated from

    Natural Gas 45.2%
    Nuclear 14.8%
    Large Hydro 11.7%
    Coal 16.6%
    Renewable 11.8%

    A minor swindle, I suppose.
  7. Jul 19, 2008 #6
    Hmmm.. using figures for the fuel source predominant in their major market... scandalous! Of course they should be making their figures look as bad as possible like every other car maker, right?
  8. Jul 19, 2008 #7

    Ivan Seeking

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Yes, I realize that. My implicit point was that these must also be considered when comparing technologies. There are hidden energy and evironmental costs for every option to petro. Cherry-picking specific data can be very misleading.

    Tesla was also claiming something like a 100,000 miles lifespan for the batteries, which is ridiculous. Shelf life alone makes that claim impossible for most drivers. And I don't know about you, but with heavy use, I need a new battery for my laptop about once a year. There is still battery life, but I need more than 30% or 40% capacity.
    Last edited: Jul 19, 2008
  9. Jul 20, 2008 #8
    Those of us who are objectively intested in these things would prefer facts over fiction. So what, you don't care or you prefer the fiction?

    The source of electricity when you plug-in your electric car is the elecrical grid. That source is not exclusively natural gas, and unlikely so if you live in the eastern United States. Unless I've missed yet another point, to claim a souce of power such as natural gas is somewhat incredulous.
    Last edited: Jul 20, 2008
  10. Jul 20, 2008 #9
    Tesla Motors claims 1.14 kilometers/megajoule performance

    If you look at the table on the webpage (http://www.teslamotors.com/efficiency/well_to_wheel.php [Broken]), the last two rows show cars whose source fuel is natural gas. The wheel-to-well ratio decreases as you go down the table. The table suggests that the selected natural gas burning cars provide less efficiency than the selected gasoline burning cars while having slightly less well-to-station efficiency. The well-to-station efficency for the Tesla roadster is the lowest of all in the list, yet the car itself is remarkably more efficent than the other cars. That's no suprise either, because the Tesla roadster is electric.
    Last edited by a moderator: May 3, 2017
  11. Jul 20, 2008 #10
    Re: Tesla Motors claims 1.14 kilometers/megajoule performance

    Last edited by a moderator: May 3, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook