Prime electric bill cost to operate

Discussion in 'Prime Plug-in Charging' started by PriusPrimeOwner, Jan 17, 2017.

  1. Andyprius1

    Andyprius1 Senior Member

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  2. Andyprius1

    Andyprius1 Senior Member

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    First assumption was wrong. Level 2 charging at $.17/ KWHRs. Charge time: less than 2.5 hours from empty.
    Daily cost = 2.5 X .17 = .34 + .08 = .42 cents a day, per charge / full charge.
     
  3. Andyprius1

    Andyprius1 Senior Member

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    I partitioned the kitchen and family room off with two doors installed at thresholds and since I had a natural gas log starter in my fireplace I connected a gas fired space heater and we are nice and toasty in the Winter. Our gas bills are less than 1/3 of the old, highly inefficient forced air system.
    Upstairs we have a Electric blanket on for about 10 min. A night.
     
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  4. Lee Jay

    Lee Jay Senior Member

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    That's some pretty bad math there, Andy.

    2.5 hours * $0.17 / kWh * (240V * 16A / 1000W/kW) = $1.63 per charge.

    You forgot to include the power draw. Essentially you assumed the power draw was 1kW. It isn't, even on 120.

    Others have reported the actual energy consumed during a full charge is 6.3kWh by direct measurements.

    6.3kWh * $0.17/kWh = $1.07 per charge.
     
    #64 Lee Jay, Jan 21, 2017
    Last edited: Jan 21, 2017
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  5. William Redoubt

    William Redoubt Senior Member

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    The only way to determine the actual cost is to install a meter or strip recorder. The cost of electricity includes the charge moved into the Prime's battery, plus all losses, which are considerable (about 15 percent or more).

    A reasonable meter (from Amazon)
    is about $150, which is the cost of a good dinner for two or one day at Disneyland if you eat your lunch in your car.

    If I had a Prime (next time I buy I will), I would consider the cost of a meter to be part of the purchase price. I don't know why such a meter is not part of the charging cable since the data it provides is so valuable.
     
  6. Andyprius1

    Andyprius1 Senior Member

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    My provider is SMUD, SACRAMENTO UTILITY DISTRICT, I can go on line and read the KWHRs used between 1200 and 0600, another option is cost for the KWHRs used that day. They always agree, i.e. 2 KWHRs usage = 2 X $.075 = ~ $.15 Total Im only looking at EV charge between 1200 and 0600. Starts at 1200 (midnight) and completed charge. Around 0200 to 0230 where am I going wrong? Was the other post perhaps Level 1 ?
     
  7. Lee Jay

    Lee Jay Senior Member

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    You equated 2 kilowatt-hours with 2 hours. Not the same units. 2 hours on charge at 1 kW is 2kWh. 2 hours on charge at 3kW is 6kWh.
     
  8. Andyprius1

    Andyprius1 Senior Member

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    For some reason, on your original reply to me you took the KWHRs and again multiplied it X 240 volts times 16 amps, I don't know how you measured 16 amperes.
    1. A Kw = 1000 watts
    2. A KWhr 1000 watts consumed in 1 hour
    3. A watt is the product of E X I, Voltage times current.

    The Kilowatthour already comprises the Voltage, the current and the the total consumption KILO

    ANYWAY I'll pass on to SMUD THAT THEY ARE DOING IT WRONG.
     
  9. Andyprius1

    Andyprius1 Senior Member

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    Where did you get 3 Kilowatts from?
     
  10. Andyprius1

    Andyprius1 Senior Member

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    Lee are you a EE ?
     
  11. Lee Jay

    Lee Jay Senior Member

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    Yes - specialty in power.
     
  12. Lee Jay

    Lee Jay Senior Member

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    Just an example.
     
  13. Andyprius1

    Andyprius1 Senior Member

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    But you incorporated that 3 Kw along with 16 amps that was completely irrelevant to the OPs comments and then put it forth as factual...?
     
  14. Lee Jay

    Lee Jay Senior Member

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    No, I was just trying to teach you how to do this calculation.

    You multiplied 2.5 hours of charge time (not 2.5 kWh of energy usage) by $0.17 per kWh. That's wrong. You need to multiply the charge time by the power draw during that time to get energy (this assumes constant draw, which isn't quite right, but close enough to illustrate the point).

    What I did was to multiply the voltage and the current that a Prius Prime draws on L2 - 240V and 16A - to get its power draw. Then I multiplied it by the charge time to get energy and multiplied that by the cost of energy to get the cost.
     
  15. EV-ish

    EV-ish Active Member

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    Sounds right.

    PV ?
     
  16. Andyprius1

    Andyprius1 Senior Member

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    Many mistakes:
    1. Both Voltage and current as given by any company are theoretical and will vary.
    2 The utility company already calculates PIE, Power = I X E, in their meter at your house.
    3. It then measures time and the watts used in one hour
    4. It also calculates all the variations which occur within any 24 hour period

    So when my Power company tells me on their bar graph that I used 2 KWHRs to charge my car, then I believe them and my cost is about $.15 for that period. TY Lee
     
  17. White 17

    White 17 Junior Member

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    I am just getting into owning a plug in so not sure how it will work out . I will guess 20 to 25 days a month. I do have other vehicles that get used also. This will be my most used I think.
     
  18. Lee Jay

    Lee Jay Senior Member

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    Quit being stubborn. This is what you said:

    "2.5 hours from empty" X "$.17/KWHRs" = ... ".42 cents a day per charge / full charge."

    That's a flat wrong calculation. You used 2.5 hours - the charge time - as an energy value. It's not. It's a time period.

    In that 2.5 hours, a Prime will actually consume about 6.3kWh of electricity by the measurements of others. One way to demonstrate that is to point out at it draws either 240V * 16A for about 2 hours (~7.7kWh) or 120V * 12A for about 5 hours (~7.2kWh). Since the charge tapers toward the end, the 6.3kWh actually measured is quite plausible.

    At your rate of $0.17/kWh, a full charge will actually cost 6.3kWh * $0.17/kWh = $1.07 per charge. You got ".42 cents" a charge. Even ignoring the misplaced decimal point, you're still wrong since $0.42 is not the same as $1.07. And it's wrong for a simple reason - you used the charge time of 2.5 hours as a unit of energy when it's not.
     
  19. EV-ish

    EV-ish Active Member

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    Looks to be missing power, as in :

    time * power * cost/kWh = total_cost
     
  20. Lee Jay

    Lee Jay Senior Member

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