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Calculating gas plus electric (overall) efficiency in a Prime

Discussion in 'Prime Main Forum (2017-2022)' started by CraigCSJ, Jul 6, 2017.

  1. CraigCSJ

    CraigCSJ Active Member

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    Prime Advanced
    It is not practical for me to measure the electricity put in my Prime, and I wonder if the following calculation is a reasonable estimate.

    The car gives me a percent of EV miles and miles/KWh. Using the car's percentage made HV miles only 34, so I assumed my HV miles were 54 per the EPA (my MPG in a gen 2 Prius equaled the EPA figure), and the remainder of miles were EV miles. I then divided the EV miles by the miles/KWh shown by the car (5.9) and divided the KWh result by 33.7 to get the gas equivalent. I then added that figure to the actual gas put into the Prime, and divided that total into the total miles driven.

    I considered adding 15% to the KWh to account for loss from plug to battery, but didn't thinking the miles/KWh given by the car included miles from regenerated electricity which probably offset the loss.

    In my case, after 1432 miles at my first gas fill, I had 150 MPG for gas only, and 101 MPG gas + electricity.
     
  2. Rmay635703

    Rmay635703 Senior Member

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    ??? This doesn't make a lick of sense.

    You burned 9.52 gallons of gas ?
    You only drove 515 gas miles ?

    I think you need to keep gas tallies and efficiency separate from EV measures

    Doing so you can figure out cost per mile and focus on improving both metrics
     
    Prius from Dad likes this.
  3. Prius from Dad

    Prius from Dad Senior Member

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    Not sure the calculations are quite right. The gas only seems very high and the gas and elec. seems to be low. Depending on the gallons filled and 1432 miles, I would say your gas and elec. mpg is somewhere around 140 mpg. I track my EV miles, my HV mpg and my daily mpg on my commute. Since Jan 31 my average EV miles driven per daily commute are 30.85. My average HV mpg is 69.67 and my average daily mpg is 120.3. In this warmer weather I'm getting 1300-1400 miles per 10 gal. fill-up. Here are some charts documenting this:

     
  4. CraigCSJ

    CraigCSJ Active Member

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    Prime Advanced
    I actually put 9.509 gallons in the tank. The car told me that 79 percent of my miles were EV. I don't believe that figure really represents how far I went on gas, because that figures around 300 miles on gas, or 21% of 1432 miles. So I assumed I went 513 HV miles.
     
  5. Prius from Dad

    Prius from Dad Senior Member

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    So with your 9.509 gallons, that makes your combined (EV and HV) mileage 150.59 mpg, for that tank, impressive. (y)
     
    priuscatprimeguy likes this.
  6. jaqueh

    jaqueh Active Member

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    You can’t use that percentage because it’s also taking into account electricity that’s being used in hybrid mode