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KWH charging meter

Discussion in 'Model S: Battery & Charging' started by O-G, May 13, 2015.

  1. O-G

    O-G Member

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    Does the MS have a meter showing how much power was drawn to charge it? Current week, month, cumulative? My ice vehicle is a business auto so all of the gas is paid for by the company. If I am now charging at home, how do I expense that to the company? Somehow I need to measure the cost of all home charging. Do I need to put a meter on the charger in the garage?

    thanks
     
  2. David99

    David99 Active Member

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    Unfortunately the Model S doesn't keep track of energy coming into the charge port. It only measures at the battery level. And even that is not very accurate. It stops counting when the car is not moving. So the energy usage shown in the trip meters are not the actual usage.
    The only way is to put a meter at your charger at home. Of course that will only measure what you need at home, not when you charge anywhere else.
     
  3. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    You can use a few products to do this if you want to meter it. The Energy Detective (TED) has a number of solutions that can help you.

    Is there any reason you don't use the mileage-based method for expenses instead of actual costs? I've found that in the Model S, the mileage-based method is much, much better...
     
  4. O-G

    O-G Member

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    When the business owns the vehicle, all expenses related to the purchase and operation of the vehicle can be charged to the business. Then, any personal miles driven become additional income at the mileage based rate. I believe that using the mileage based method you suggest is common when it is a personal vehicle but driven some amount of business miles.
     
  5. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I believe - although I'd have to check with my tax planner again - that you can use the mileage-based approach to handle car-related expenses even if the business purchases the vehicle.

    I did the calculations a couple of years back - the biggest challenge for the Tesla was the depreciation expense limit when you used the total cost approach. Unless you simply didn't drive the car much and wanted to keep it for a very long time, I found the mileage-based expense came out better than total costs. The situation is likely different for everyone, but it's something to consider.
     
  6. gavine

    gavine Petrol Head turned EV Enthusiast

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    How exact does it need to be? Can you just record the miles driven and compare it to your lifetime wHr/mile average? So, if you're lifetime average wHr/mile is 320 and you drove 1,000 miles this month, you could expense 320kWh @ $0.15 per kWh (or whatever your utility rate is).
     
  7. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    #7 FlasherZ, May 15, 2015
    Last edited: May 15, 2015
    The IRS publishes a rate for deduction. You record the miles driven, and then can deduct a certain amount per mile. This year it's 57.5 cents per mile driven: Standard Mileage Rates

    Here's a quick description of the difference between the two:
    Standard Mileage Rate or Actual Expense Method: Which Is Better? - MileIQ Blog

    Because the Model S costs significantly less to operate on a per-mile basis, and depreciation expense is limited, it might be favorable. Section 179 limits depreciation on a passenger automobile to $11,060 per year, and there is no first-year "bonus depreciation" (yet) for this year (which is why businesses want to lease high-end cars). So if you drive more than 20-25k miles per year for business, it may be better for you to take the all-in mileage-based expense vs. total cost with Model S. Last year, some taxpayers got a great deal on the actual expenses method because they could depreciate 50% of the car's value for cars placed into service in 2014.

    Publication 463 (2014), Travel, Entertainment, Gift, and Car Expenses talks about it.

    I think we're going quite off-topic, though... :) You'll find that TED units work pretty well if you want to measure the kWh going into the car.
     
  8. gavine

    gavine Petrol Head turned EV Enthusiast

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    The energy meter/trip computer also keeps track of total kWh used. So, you can reset it each month and just use the total for your use. I realize this doesn't account for charging efficiency losses, but it still pretty close.
     
  9. mknox

    mknox Well-Known Member

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    Not really. Mine is off by 25% or more. I have a meter on my power outlet and track all of my away-from-home energy use as well. When I run those numbers against the car's calculation, it's way off. The number Tesla reports is useful for determining how efficiently you're driving, but does not account for the inefficiencies when charging the car, vampire losses and so forth. You can't depend on it for telling you how much energy went IN to the car.
     
  10. HankLloydRight

    HankLloydRight Fluxing

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    I use this device in two places:

    elite classic - home power monitor

    Assuming your charging outlet is on a 240v separate breaker, you can attach the current taps on each hot line to the charging socket, and measure exactly how much power is being consumed during charging. You can also enter your kWh rate from the utility, and it will tell you exactly what the power charges are.

    There's also the: elite engage hub system - home energy gateway if you want to monitor your usage online. It's really pretty cool.

    There are lots of other watt meter devices out there too, some like this one (with inductive sensors or "CTs" ), and others that install inline with the power lines.
     
  11. O-G

    O-G Member

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    The past couple of vehicles I have purchased were above the 5K GVWR. That put them out of the automobile category and into the equipment category. The first one quite a few years ago, I was able to completely expense in the first year. There are some limitations now, so the BMW X5 in 2009 was limited to 50% in the first year. I assume that the GVWR of the MX will allow me to do the same. That is why I believe it is better to have the company purchase the vehicle and have all expenses paid by the company vs the standard mileage rate.
     
  12. beeeerock

    beeeerock Active Member

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  13. davewill

    davewill Member

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    #13 davewill, May 17, 2015
    Last edited: May 17, 2015
    For cheap, simple and accurate, you can always go with HialeahMeter.com. Less than $40 for the meter and socket, plus some conduit and wire. You can install this inline before the wiring enters your EVSE. Just take a reading each month and subtract the precious month's reading. It can be tricky to read if you're trying to get sub-1kWh numbers like to measure a single, short charging session, but for the use you describe, it would be perfect. No need to record more accurately than to the kWh. Any rounding will even out the next time you take a reading. Click on the pictures to see details.

    yhst-97927213475128_2272_221519.jpg
    yhst-97927213475128_2272_1931018.jpg
     
  14. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I imagine model X will have a GVWR > 6,000, since Model S's GVWR is 5,700+, so at least you won't be limited by the passenger car rules. However, right now it only makes a few hundred dollars of difference. Bonus depreciation is a moving target. Currently, in 2015, it's gone and the limits are back to $25k. Congress may attach the upper limits (farmers are lobbying for the change) as a rider before the end of the year, but you can't guarantee that this year.

    Last year was a great deal - bonus depreciation allowed for people to take half the vehicle cost as a depreciation expense for vehicles put in service in 2014. That's gone this year and your limit is $25k (which isn't bad, you can accelerate the depreciation to 5-6 years, depending on how you configure Model X).

    Model S is still subject to passenger car rules, $11k limit.

    See your tax advisor, yadda yadda.
     
  15. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Apr 1 - May 1

    Miles driven: 2039

    Total electricity used (house): 1146 kWh (per smart metre)

    Each 15 minute period while charging: 2.2 kWh for 1.75 hours (2.2 - 0.25) = 1.95 * 7 * 31 = ~423 kWh (per smartmetertexas.com)

    Each 15 minute period while not charging: 0.25 kWh (0.25 * 4 * 24 * 31) = 744 kWh (per smartmetertexas.com)

    Sanity check: 1146 - (423 + 744) = 1167 ; 1146 - 1167 = -21 = 1.8% (close enough for government work)

    Supercharger miles: ~400 ; ~20% of miles

    Electricity used (from Tesla display): 471 kWh = 471 * 0.8 = 377 kWh from home charging ; 94 kWh from SC

    Difference between display reading and home charging: 423 - 377 = 46 kWh = 423/377 ~= 12% loss.

    Percent of home electricity used by Model S: 423 / 1146 ~= 37%

    Charging amps: 33

    Electricity cost: $0.06522 / kWh

    Connection charge: $34.93 / month

    Tax: $1.06 / month

    Total: $106.58

    Cost of Model S: 106.58 * 0.37 = $39.22

    Cost per mile driven from home charging: 39.22 / (2039 - 400) = $0.024 / mile + 1.8% ($0.025 / mile)
     

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