KWh/ Mile? Justifying 19 cent KWh electric rate

Discussion in 'Prime Plug-in Charging' started by kearsarge, Dec 12, 2016.

  1. kearsarge

    kearsarge Junior Member

    Joined:
    Jul 2, 2010
    25
    20
    0
    Location:
    Northeast
    Vehicle:
    2017 Prius Prime
    Model:
    N/A
    While looking for a new v, I came across the Prime and factoring in the federal and state tax rebate in Mass. it seemed to be a great deal... until I calculated how much my "savings" would be for using electric charging.

    Basic math 8.8 kwh * 19.2 cents per kwh=$1.69 per 25 miles of range or $3.38 per 50 miles. Doesn't look so great when gas is just above $2 per gallon and will get me the same range.

    Anyone else in the same boat? Does that math make sense? Assuming you all include all the various variable dissemination and distribution fees into your electric rate...

    Is there anyone else buying a prime that might not plug it in? Any consideration for the life of the high compression ICE?
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    89,477
    40,050
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    i think it only takes 6.7kwh X .19 = $1.28

    we pay .24/kwh, so ev driving isn't a bargain, but that's not the reason i drive it. nonuse of gasoline is wonderful for a variety of reasons. and gas won't be 2 bucks forever.

    what do you mean by high compression ice, it's the same as any other prius. if you don't plug in, you'll be just like a lift back towing around a couple hundred spare pounds, like a lot of people in california carpool lanes.:p
     
    Jan Treur, giora and EV-ish like this.
  3. Lee Jay

    Lee Jay Senior Member

    Joined:
    Jun 25, 2009
    5,004
    3,640
    0
    Location:
    Westminster, Colorado
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
  4. fotomoto

    fotomoto Senior Member

    Joined:
    Apr 22, 2009
    5,155
    3,417
    0
    Location:
    So. Texas
    Vehicle:
    Other Hybrid
    You have to factor in charging efficiency too. A (very) loose rule of thumb is to use the battery's full capacity (8.8 in this case) as the multiplier to account for the inefficiencies of both the EVSE and the cars' internal charger. So, the OP is getting a closer real world figure for a full charge by using 8.8 x .19. Best to over estimate.

    It gets cloudy when one has to factor in level 1 vs 2 charging as the latter units are typically more efficient.
     
    bisco likes this.
  5. Lee Jay

    Lee Jay Senior Member

    Joined:
    Jun 25, 2009
    5,004
    3,640
    0
    Location:
    Westminster, Colorado
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    Two people who have just measured the charge amount got (from memory) 6.3kWh and 6.7kWh from depleted Ev to full.

    What you're missing is that the Ev range of the battery stops when the battery gets to something like 20-25%. The rest is reserved for Hv mode hybrid operation. 33.7kWh/gasoline gallon equivalent divided by 133MPGe = 253Wh/mile. Multiply by the rated range of 25 miles and you get an energy consumption - at the wall - of 6.3kWh.
     
  6. fotomoto

    fotomoto Senior Member

    Joined:
    Apr 22, 2009
    5,155
    3,417
    0
    Location:
    So. Texas
    Vehicle:
    Other Hybrid
    If I'm reading this right, you're saying there's a 100% charging efficiency (6.3 in and 6.3 out).
     
  7. Lee Jay

    Lee Jay Senior Member

    Joined:
    Jun 25, 2009
    5,004
    3,640
    0
    Location:
    Westminster, Colorado
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    No - MPGe is calculated from wall energy, not battery energy.

    Miles per gallon gasoline equivalent - Wikipedia

    "For EPA, this considers the tank-to-wheel for liquids and wall-to-wheel energy consumption for electricity, i.e. it measures the energy for which the owner usually pays. For EVs the energy cost includes the conversions from AC to charge the battery.[33]"
     
    #7 Lee Jay, Dec 12, 2016
    Last edited: Dec 12, 2016
    Nic Steussy and giora like this.
  8. EV-ish

    EV-ish Active Member

    Joined:
    Nov 17, 2016
    602
    277
    0
    Location:
    SW US
    Vehicle:
    2017 Prius Prime
    The sizes and cargo carrying capacity are quite a bit different.

    If fuel cost is your only consideration then two other things come to mind:
    1. You are hedging future gasoline prices with the Prime. Remember that OPEC wants to charge ~ $60/barrel and might be getting their act together
    2. A Prime gives you the option of enjoying cheaper electricity in the future through things like home or community solar.
     
    #8 EV-ish, Dec 12, 2016
    Last edited: Dec 12, 2016
    Nic Steussy likes this.
  9. fotomoto

    fotomoto Senior Member

    Joined:
    Apr 22, 2009
    5,155
    3,417
    0
    Location:
    So. Texas
    Vehicle:
    Other Hybrid
    So from the two reports the average used in EV is approx. 6.5kWh. How much is required from the wall to charge it back to full?

    For example, my Energi uses around 5.5-5.7 kWh from its 7.6kWh pack but needs about 8 kWhr from the OEM level 1 charger to fill it.

    Common Electricity Questions for the C-Max Energi | C-MaxChat
     
  10. EV-ish

    EV-ish Active Member

    Joined:
    Nov 17, 2016
    602
    277
    0
    Location:
    SW US
    Vehicle:
    2017 Prius Prime
    I do not know *exactly,* but the Prime useable is somewhere in the 5.2 - 5.5 kWh range and charging losses varies from ~ 15% using a 240v charger and ~ 20% using a 110v.
     
  11. Lee Jay

    Lee Jay Senior Member

    Joined:
    Jun 25, 2009
    5,004
    3,640
    0
    Location:
    Westminster, Colorado
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    6.3kWh, according to the EPA. 33700Wh/gallon / 133 MPGe * 25 miles = 6,334Wh.
     
    #11 Lee Jay, Dec 12, 2016
    Last edited: Dec 12, 2016
  12. DonDNH

    DonDNH Senior Member

    Joined:
    Feb 3, 2004
    1,711
    650
    0
    Location:
    Nashua, NH
    Vehicle:
    2016 Prius
    Model:
    Four Touring
    Have you checked with your electric company to see if you can get a cheaper rate? I was able to put a second electric meter on a water heater in order to get a reduced rate.
     
  13. Rmay635703

    Rmay635703 Senior Member

    Joined:
    Oct 16, 2016
    1,570
    1,021
    0
    Location:
    Somewhere in Wisconsin
    Vehicle:
    2013 Chevy Volt
    Model:
    N/A
    Has anyone real world hypermiled the Prime in ev and gas modes to determine its true upper efficiency limits?

    If it's like my volt
    +20% is possible on gas
    And +100% on ev

    The benefits of the prime are that it really costs no more than a normal prii but gives energy choice.

    You may we'll find the prime is still cheaper in town real world on electricity,

    You will also find you can drive the prime on gas only

    And solar or the possibility of increasing fuel prices make the prime a no brainer
     
  14. fotomoto

    fotomoto Senior Member

    Joined:
    Apr 22, 2009
    5,155
    3,417
    0
    Location:
    So. Texas
    Vehicle:
    Other Hybrid
    I understand the math but reality can often be different sometimes more so. For instance, the Gen1 Volt 16kWh battery should only need 13ish kWh but sometimes it pulls 14.5-15 kWh due to heavy HVAC cooling use during the summer. Battery temps are another factor.

    Like I said, my "rule" is very loose and over estimates on purpose. As the saying goes, YMMV.
     
  15. pricoaster

    pricoaster Member

    Joined:
    Aug 21, 2006
    66
    65
    0
    Location:
    Los Angeles
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Premium
    I recharged from "empty" at a public station in Vegas. The registered kWh added was 6.3. The other day I recharged at a local public station but I wasn't fully empty (if I remember correctly, maybe had around 4-5 miles left). It did fully charge and 5.3 kWh was added.
     
    breakfast, Rmay635703 and EV-ish like this.
  16. Rmay635703

    Rmay635703 Senior Member

    Joined:
    Oct 16, 2016
    1,570
    1,021
    0
    Location:
    Somewhere in Wisconsin
    Vehicle:
    2013 Chevy Volt
    Model:
    N/A
    [QUOTE="fotomoto, post: 2462675, member: 49996]For instance, the Gen1 Volt 16kWh battery should only need 13ish kWh but sometimes it pulls 14.5-15 kWh due to heavy HVAC cooling use during the summer. Battery temps are another factor.

    Like I said, my "rule" is very loose and over estimates on purpose. As the saying goes, YMMV.[/QUOTE]

    If you short fill the volt (don't charge fully) you sometimes find the kw in is under 5% different

    Around here battery cooling runs under a week a year
     
  17. inferno

    inferno Senior Member

    Joined:
    Jun 23, 2013
    1,070
    403
    0
    Vehicle:
    2010 Prius
    Model:
    III
    What incentives in Mass? I see the old pip on there but not the prime. Also, take into count gas will go back up... It already has. And if the prime blends you might save money anyway. Gas and electric will fluctuate.

    If gas is cheaper electric might go down or stay the same to compete.
     
  18. kearsarge

    kearsarge Junior Member

    Joined:
    Jul 2, 2010
    25
    20
    0
    Location:
    Northeast
    Vehicle:
    2017 Prius Prime
    Model:
    N/A
    1) Agree. Bought my current 2GEN for lifecycle costs with my 90 mile commute (frugal yankee) and as a quasi political statement on foreign policy / national security (concerned veteran). Adjusted hedging #s below.
    2) Would have by now but plan on moving in next 3 years. Maybe then...

    Idea behind v was to replace current vehicle and provide some option to economically keep miles off the wife's highlander. In reality, I think we love the room of the highlander and wouldn't often switch it up for family trips. With only 2 young kids the 4 seat prime wasn't out of the realm of possibilities for my daily driver and I was impressed with the handling and tech (safety + big screen). The dealership has a Prime Premium and 2017 v four at about the same price. Given the 6k in tax incentive and say 2-3K in lifetime savings of gas mileage the cost differences were real.

    Aggregating the above helpful comments and assuming my 110v status quo, I can adjust my estimate to 7kw per 25 miles would be $1.33 or rough equiv of $2.70 in gas. Much better hedge for a projected 8 year time span than my first calculation.

    Lastly, I wish they would announce on the 2018 v. Will it be PHEV?
     
  19. kearsarge

    kearsarge Junior Member

    Joined:
    Jul 2, 2010
    25
    20
    0
    Location:
    Northeast
    Vehicle:
    2017 Prius Prime
    Model:
    N/A
    No luck on community aggregate deal. Maybe if I move..

    True. The link on the 1500 incentive leads to the Prime. Assuming it will be 1500 or maybe even 2500.
     
  20. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    89,477
    40,050
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    no plug for the v in the near future.
     
    mertechperformance likes this.
Loading...