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Does anyone have long-term energy data measured at their electric panel?

Discussion in 'Electric Vehicles' started by ToddRLockwood, Jan 20, 2015.

  1. ToddRLockwood

    ToddRLockwood Active Member

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    I'm looking for someone who has measured their energy usage for one year using the following criteria:

    • The car is a Model S P85 or P85+
    • The energy usage is measured at the main electric panel, but only for the car charging circuit.
    • The charging circuit delivers a true 240V/40A to the vehicle.
    • The location includes real winter conditions.
    • The car has not been charged away from home during the one-year period.
    • Distance driven for the year is known.
     
  2. mknox

    mknox Well-Known Member

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    I have some of that... for almost two years.

    Problem is, I'm on a 20 amp 240 volt circuit (charging at 16 amps) and I very frequently charge away from home, but I do track it.
     
  3. ToddRLockwood

    ToddRLockwood Active Member

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    I was probably way too specific with my request. How do your measurements compare with the energy usage displayed in the car?
     
  4. mknox

    mknox Well-Known Member

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    They're way off. I have a spreadsheet at home that I'll try to copy and post here. I'm pretty sure that the car is only measuring and reporting what comes out of the battery as you drive. I don't believe it is accounting for inputs like charger inefficiencies, the pumps and fans that run when charging nor the vampire drain that occurs as the car sits.
     
  5. RAM_Eh

    RAM_Eh Member

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  6. ThosEM

    ThosEM Space Weatherman

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    Todd,

    I have convinced myself that the voltage and current reported during charging is reasonably accurate, within a few percent, and I doubt there are significant losses between the meter and the connector in my setup. I base that on having a Smart meter that gives me hourly consumption data from my electric supplier. I see between 230-240 V and 40 A, or 9200 to 9600 W on the charging dialog or in the app. The consumption seen on the BGE web site is always a bit under 10 kW if charging is continuous for more than an hour (since hourly averages are posted), when other loads are negligible (shutting off other big loads, such as heat pump, dryer, oven, etc.). So the electric company agrees well with the data presented in the car, and my billing is based on the electric company data. kWh into the car can be gotten from the power observed at the dialog and the duration of the charging, given by App notification start/stop times.

    App notifications also give us battery SOC as rated range added, and that translates into kWh stored in the battery, knowing rated consumption (189 Wh/km for my MS). When I compare the reported energy at the connector as described above to the energy reported as being stored in the battery as described above, I get 91-92% rectifier efficiency. Others have reported values as low as 80-85%, but I don't get such low values with this method.

    After looking at those numbers I'm generally satisfied that I'm being charged for a reasonable amount of electricity, and pleased to see such high charging efficiency. So, while it might be interesting to know just how much electricity goes to the car, I'm not motivated enough to invest in a separate meter, and I can get a good estimate by just tracking it on the trip meter and adding 10%.
     
  7. ToddRLockwood

    ToddRLockwood Active Member

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    Thanks, Thomas. I've heard other owners mention a 10% charging efficiency loss as well. Also, given that the energy meter (on the right side of the speedometer) responds to all use of energy in car (cabin heating, battery heating, headlights, etc.), not just the motor, the Wh/mile value on the touch screen is probably a fair indication of all energy consumed.
     
  8. RAM_Eh

    RAM_Eh Member

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    I have very accurate data for October, November and December. Once I remove the personal data off the forms I will post. I am involved with our local utility studying charging patterns.
     
  9. qwk

    qwk Model S P2681

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    Not even close. The Wh/mile number the car displays, doesn't include vampire, and losses while the car is in Park. If you get 333Wh/mile displayed, its more like 370-400Wh/mile in the summer, and 500+Wh/mile in the winter(winter with cold temps.) from the wall.
     
  10. swaltner

    swaltner Member

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    While it's not for a Tesla, here's the data from my 2013 Leaf SV.

    Screen Shot 2015-01-21 at 11.31.45 PM.png

    - My cost for electricity is all over the place due to my solar panels. I only "charge myself" money for feeding the Leaf in months that I actually pay for electricity consumption. If I paid for 200 kWh of electricity and the car used 300 that month, I put the cost for that 200 kWh on the spreadsheet. If I paid for 400 kWh and the car consumed 300 kWh in a month, I put down the cost of the 300 kWh. When I'm paying for electricity, it comes out to 11 cents/kWh right now.

    - My kWh column is a reading on the power flowing through the EVSE at the house using a TED 5000 monitoring system. The "kWh (Carwings)" column is what the Leaf reports that it consumes. Like the Tesla, this is what's pulled out of the battery. Carvings does not account for charging losses. The vampire losses on the Leaf are minimal.

    - I rarely charge away from home. I tend to do it more in the winter, due to pushing the limited range on the Leaf. When I do, it's generally a couple hours on a 120V outlet or 15 mins on a 208V/30A EVSE, just to get enough to get me home. I'd be surprised if I leeched 30 kWh in a single month.

    - Ignoring the limited charging away from home and converting my highest and lowest efficiency ratings to Wh/mi yields 234 Wh/mile in Oct 2014 (4.27 mi/kWh) and 361 Wh/mile in Feb 2014 (2.77 mi/kWh). This means I consume 54% more energy for a given distance in the dead of winter compared to mild temps in the fall. Another way to state that is that the added consumption decreases my available range by 35%.

    - I liberally use the preheat function while connected to shore power. So while I'm using all that electricity, the actual hit on my range isn't quite as bad as the 35% loss that I calculated, since the battery maintains close to full charge during the preheat sequence. It's probably closer to a 25% reduction in range.
     
  11. RAM_Eh

    RAM_Eh Member

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    The following is only for home based charging. I rarely charge outside of home. Once or twice a month at the closest supercharger. I am putting a data logger on my car in the next few weeks to show all charging...even away from my home charger.

    View attachment Oct to Dec 2014 (2).pdf
     
  12. PatD

    PatD Member

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    Tell us more about this data logger. . .
     
  13. RAM_Eh

    RAM_Eh Member

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    I have been approached by my utility as I am part of another program studying the effects of charging on the utility system. A separate program wants to see what the car is actually doing both at "home" and "away". This is the company involved with Toronto Hydro doing the project. I have given consent to having the logger installed in my vehicle. Part of the program the utility will be able to reduce my charging...but I will get a message (text and email) allowing me to override them. Since I do most of my charging overnight I don't see an issue.

    http://www.mycarma.com/products/myev/
     
  14. mknox

    mknox Well-Known Member

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    Here is a snap of the spreadsheet I use to track my useage. I do my best to accurately track energy from outside the home to add to what I know from my energy monitor on the car's charging circuit.

    View attachment Monthly Energy.pdf
     

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