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Electric Bill 50% Higher Since Purchasing 2 Months Ago

Discussion in 'Model S: Battery & Charging' started by amans232, Sep 30, 2014.

  1. amans232

    amans232 Member

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    Got my car 2.5 months ago MS60...and my electric bill is up around 50%...here are some stats

    2012
    July kWh=936
    Aug kWh=1959
    Sept kWh=1566

    2013
    July 1068
    Aug 1775
    Sept 1435

    2014
    July 1495
    Aug 2550
    Sept 2129

    As you can see, my numbers are a lot higher (kWh per month) than in the years past. I drive about 1000 miles per month, so I didn't expect my electric bill to be 40-50% higher than in years past. Am I doing something wrong? I should mention that I've usually been charging my car at very low amperage (usually between 6 and 10) because I read that this is better for the battery.
     
  2. dsm363

    dsm363 Roadster + Sig Model S

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    There is really no need to charge at such a low amperage. It may even be less efficient.

    It is a little tough to compare years as weather may be slightly different from year to year. For August 775kWh at 350 Wh/mile would give about 2,200 miles if my math is correct. Are you sure there aren't other factors?
     
  3. TexasEV

    TexasEV Active Member

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    Don't know where you read that but it certainly didn't come from Tesla. The car is made to charge at 40A (or 80A with dual chargers). Do it.

    - - - Updated - - -

    It's definitely less efficient to charge at such low amperage.
     
  4. ecarfan

    ecarfan Well-Known Member

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    My electric bill increased about 75% after getting my Model S. It increased about $60/month and I saved over $250/month on gasoline. A bargain!

    To the OP: don't charge at such a low amperage. Do you have a 220 or 240V outlet available?
     
  5. richkae

    richkae VIN587

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    Yes you are doing something wrong. Charging at low amperage is not efficient. I don't know where you read that it is better for the battery, but it is almost certainly wrong.
    I would suggest charging at somewhere between 32 and 40 amps.
    A study on the most efficient charge rate for the Model S has not been done, but it has been done for the Roadster. Tesla Roadster Charging Rates and Efficiency - Tom Saxton's Blog
    The Roadster was found to charge most efficiently between 32 and 70 amps.
    Very little difference was found between 32 and 70 amps, but below 24 amps was found to be very inefficient. 12 amps was more than 50% less efficient than 40 amps.
    Without other evidence to consider, the Model S is probably similar.
     
  6. dauger

    dauger Member

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    Are you on Time-Of-Use metering? TOU for short. I'm able to charge at 10c/kWh from midnight to 6 am. Then I rescheduled everything possible to those hours: pool equipment, the dishwasher, etc. The difference saves me over $100 per month, more with solar because I sell my solar energy at 28c/kWh by day. I can't tell where you are located to find out what power company you use.
     
  7. Tedkidd

    Tedkidd Member

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    Looks like about 600 kWh per 1000 miles. I believe a higher rate will knock 100-150 of that.

    What were you spending before to go 1000 miles?
     
  8. Yggdrasill

    Yggdrasill Active Member

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    I'm not convinced the entire increase is due to the Model S. Accoring to the data, your consumption has increased by around 650 kWh per month. That would be about 650 Wh/mile, while a more normal consumption would be about 400 Wh/mile, including charging losses. Achieving 650 Wh/mile in a 60 kWh Model S just seems unrealistic to me, without being very aware of it. And suggests to me that there have been some other variations involved.

    See how the consumption varies over a longer time span. And there's nothing wrong in increasing the charge rate, it will increase efficiency to a degree. (But not enough to reduce consumption by 250 Wh/mile!)
     
  9. Chickenlittle

    Chickenlittle Active Member

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    Have you done any controls at all in this experiment? Weather difference? Other appliances changed? Only control is the months compared
     
  10. Alysashley79

    Alysashley79 Member

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    Also if you take a look at teslas website it'll tell you that it will cost you more $ to charge at lower amperages than if you charge at 40 amps vs 10 amps. Take a look at the calculator.
     
  11. amans232

    amans232 Member

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    OK, thanks for all the feedback. I will try to address some questions that arose.

    1) So far I have driven 2900 miles over about 11 weeks. My average Wh/Mile is 333.
    2) My electric bill usage is pretty predictable with peak usage from June to Sept due to heavier AC usage (I live in Florida). There really is no weather differential that applies in my case - in my opinion, here in South Florida. We have not purchased any other appliances.
    3) My actual dollar increase amounts to about $80-$100 a month extra so far.
    4) I have a 240V outlet. The recommended NEMA 15-50 is installed.
    5) I will start charging at 40 amps from now on!!!
    6) I was spending about $250 a month on gas before, and was expecting to pay about $20-$30 extra a month on electricity.
     
  12. Ed Chan

    Ed Chan Member

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    By my calculation, you should be using about 421.4 kWh/month for your car. Depending on your marginal electrical rate, you will be paying the following amounts:
    RateElectrical Cost
    0.1042.14
    0.1563.21
    0.2084.28
    0.25105.35
    0.30126.42
    0.35147.49
    0.40168.56
    0.45189.63
    0.50210.70
    As you can see, it can really add up, especially if your marginal rate is high. In SoCal, there is a Time of Use plan that basically gives me $0.10/kWh electricity between 12am and 6am. In return, I pay very high prices between 10am and 6pm. If you're on a general tiered plan with your electric co., maybe give them a call and see if they can help you choose a plan that is more beneficial to your electric car charging. If I never changed plans, I'd basically be paying $0.35/kWh for my charging, which makes the value proposition of an electric car much less.
     
  13. tga

    tga Active Member

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    #1 - Remember, 333 Wh/mile is consumption from the pack. You will draw more than that from the wall, to account for charging losses (heating in the wires, charger, and battery; running the cooling system, etc). I forget the overhead, maybe 10%? But it's not enough to explain the entire delta

    #2 - You should be able to normalize your AC usage year-to-year and month-to-month by looking at cooling degree days (assuming the same thermostat settings). Without confirming that that temps have been the same, it's impossible to tell how much of the excess use may be due to increased A/C usage.
     
  14. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Active Member

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    How were May and June?

    Charge the car at a higher current, off-peak overnight then see how things go. Low current charging is inefficient, and especially so in a Model S.
     
  15. GoBlue88

    GoBlue88 Member

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    #5 will help you right away. Agree with the others that you should check if there are TOU rates available from your utility for further savings.
     
  16. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Active Member

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    He's in South Florida so there should be TOU. 1,000 miles per month isn't that month, so other usage will really determine whether it's worth it. Insulation isn't just for cold places!
     
  17. jstepy

    jstepy Member

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    I too am in So Cal with the Time of Use - EV rate... I do all my charging on my HPWC (70 AMP) from 12-6 am like others on that super off-peak rate. I also take advantage of this rate by running the pool, dishwasher delay etc. Having solar is great cause during Peak Hours my production is at it's highest. Pre-Model S I always had a good surplus every month... I now just have a little one every month... so far I have been powering the Tesla for free!!!
     
  18. ElSupreme

    ElSupreme Model S 03182

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    I over doubled my energy consumption after getting the Model S (I drive ~2000 miles a month). And my power bill went up ~$40, which was about a 30% increase in non-AC months, and about ~15% increase in AC months. Versus the ~$300-350 a month I was spending on gas. It is a huge savings.

    I did switch to ToU rates where I live. It is saving me some money because ~60% of my energy consumption is between 11pm and 7am.
     
  19. romp

    romp Member

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    How did June 2014 compare to June 2013, i.e. how did year-over-year go before you got the car? I'm asking because I think you have other energy sinks in the house. Here's why:

    * for the 1000 miles/month with 333 Wh/mi you should be consuming about about 360-400 kWh/month at the outlet side (for 30-80A charging, also ~ my numbers)
    * according to your data your total added year-over-year consumption is ~600 kWh/month. That's 200 kWh/month extra that we need to account for
    * if you're charging at 10A * 240V, that's 2.4 kW at the outlet. This means that in order to put the whole month worth of 400 kWh into the batteries, the car was charging for 400 kWh / 2.4 kW = 166 hours total per month (not plugged in: just charging)
    * if we were to assume that whole 200 kWh/month extra was consumed by the car during charging, that means the car/chrger was consuming 200 kWh / 166h = 1.2kW extra while charging (not plugged in: just charging)

    1.2 kW is A LOT of power to dissipate. This power can only go into heat, realistically speaking. Here are some other devices that dissipate 1.2 kW: Amazon.com: area heater 1200W

    My point is that you probably would've noticed increased temperatures in your garage while charging. Since you didn't notice that, this means that this 200 kWh/month extra was consumed by something else in the house, hopefully at slower rate. Lets assume you have a new device that's always on, like a new computer or a new AC, or a fountain, etc. If it consumes only 280W, but is always on (e.g. my computers together definitely consume more than that), that would account for 200 kWh/month of consumption that you're seeing.
     
  20. ThosEM

    ThosEM Space Weatherman

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    Not sure if anyone has pointed this out, but you can use your trip meters to record how much energy you've used. Just keep in mind that it does need to be adjusted for charger inefficiency, so the power into the battery will be about 85% of the power out of the wall socket. Then that can be compared with what you believe to be the difference in your monthly bill.
     

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