Model 3

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Battery Charging kWh Compared To Electric Bill Change

I've put 16,000 miles on my Model 3 and according to the Tesla I've used 3723kWh to charge in just over a year of usage. I've done 99.5% of the charging at home. Over 12.8 months that's an average of 290 kWh per month.

I've lived in this home less than 2 years and I have only 6 months to compare year vs year energy usage. Over those comparable 6 months our energy usage has increased by an average of 500kWh per month. If the Tesla accounts for 290kwh per month I've still got an unexplained increase of 210 kWh per month.

This is a 40 year old home that is not energy efficient. There are many different things that could cause the increase and I'm trying to figure it out

Has anyone verified that the energy input into a Tesla is accurately recorded by the car?

Comments

  • edited October 2019
    The car will register how much energy is put into the car. It does not account for losses from the meter to the charge port.
  • edited November -1
    We put an inexpensive meter on our breaker to measure the usage there, and it was +/-2kwh over the course of a month from TeslaFi's "used" figure. Note that they provide both an "added" (what the car accepts) and "used" that accounts for the line losses. We've found the used to be fairly accurate -- certainly not 210 kwh/month difference.
  • edited October 2019
    just thought of this now that i've read the OP post twice. Sounds like your car is working fine, and the real mystery is finding out what is using 210kWh per month. Possible candidates are air conditioners, refrigerator, do you cook alot? or electric hot water heater?
  • edited November -1
    My utility breaks down my usage hour-by-hour for me, and if I attribute 100% of the kWh from midnight until the charging has clearly stopped to my cars, it's pretty close to what Tesla says. (I checked this for the first two months I had the car).

    As a double check, I looked at all the energy from midnight to 6 a.m. (my utility nicely totals this for me each month). There's more here than my cars, since I run my dishwasher and laundry during this time, plus on weekdays I'm getting ready for work. Still, if 100% of this is car use, I use about 10% more energy than Tesla says. I feel good enough about this to say Tesla is right, because I can see my energy spike up quite a bit during the 5-6 a.m. hour when I'm not charging cars, but am getting the household up.
  • edited October 2019
    I have a kWH meter on my breaker to my 14-50 receptacle. I keep a spreadsheet on my charges to compare the Trip Meter kWH to the my kWH meter. I have had my car for 1 year and 15k miles.

    My average difference between kWH meter and Trip Meter is +15%. I have seen it as high as 30% in frigid winter weather and as low as 10% in mild weather.

    The difference includes Charging Losses, Vampire Drain, Pre-heating, Pre-cooling, AC and accessories while not in gear, etc. Basically any power usage without being in gear. The Trip Meter only records power usage when in gear and with wheels turning.

    @BigHorn seems to have the most experience with Tesla S and 3 and charging data. He also gives this +15% factor to add to the Trip Meter kWH for charging losses, etc.
  • edited October 2019
    hokiegir1 suggested an inexpensive meter so i wanted to expand that thought as I have several meters for all my solar, geothermal and hot water systems. You can get clip on meters like below which do not normally require an electrician to install.
    https://www.altestore.com/store/meters-communications-site-analysis/solar-monitoring-systems/efergy-elite-energy-monitor-p10892/ Similar are available from ebay for cheaper but wireless range is less. Enjoy the car, 11 months for me so far.
  • edited November -1
    First: The discrepancy is small (equivalent of 2-3 incandescent or 1 halogen light(s) on continuously)... So it really could be just other changes over that 1 year period...

    But could it be "just" the car?

    It's my understanding that the Tesla trip meter includes only power used to charge the battery. When the car is plugged in, it will use power for any non-charging activities (climate, MCU, ECU, etc.) directly from the AC connection without adding that to the trip meter total. Normally, your car would be asleep most of the time it is plugged in, so the power draw would be minimal.

    Interestingly: 210 kWh/month is about 290W/hr, which is around the power draw for an awake Model 3.
    Theory #1: Maybe your car is never sleeping while being plugged in? Could that happen if your key (FOB/Phone) is too close all day?

    Theory #2: You are using L1 charging (120V). With 16000 miles and L1 charging and 4 mph of charging, that takes nearly 166 days of continuous charging (or about 50% of day). I don't think the vehicle sleeps while charging, but will still consume that 250W of constant power while awake in addition to the charging power. I don't think the 250W of standby power is included in the trip meter numbers. On top of that (or maybe because of that), 120V charging is less efficient, and those losses are not counted in the trip meter numbers either.

    One way to tell if the car is sleeping: when you open your Telsa app at home, does the car respond with its status right away?, or do you see "waking up" at the bottom of the screen for 15-30 seconds?... If you never see that message, then your car may have a sleeping disorder.
  • edited October 2019
    Other things that could account for the increase could be warmer or colder temps than the time your comparing it to . AC running on the house more or furnace running blower motor using more electricity etc. projects in garage ? Doing welding grinding etc.
    I have been comparing my bills from last year and they haven't gone up much at all. No where near what your seeing. I only drove about 7000 miles in the last 12 months though.
  • edited October 2019
    Posers. :-) Between our S and 3, we consume 900-1100kWh/month.
    Thank God for solar!
  • edited October 2019
    210KWh isn't very much, a lot of things could account for it. My window air conditioners consume 600KWh a month.
  • edited November -1
    @watermanhfl and @hokiegir1
    Thanks a lot for your posts.

    Based on those, I started to then look on youtube for videos on installation and found one showing various product brands for the same type of thing. My solar PV;s are all installed and just waiting for the final inspection and hookup. I really quite like some of the smarter monitors that will identify the devices using power based on their power profiles. Super duper cool. Sense is the one I am leaning towards right now and having that data available for all my devices and my car will really help me look at consumption.
  • edited October 2019
    Yeah I also concur with the +15%.
  • edited October 2019
    28927 miles
    7745 kwh on the car
    8135 kwh on the meter (dedicated)
    35 SC stops
    725 kwh billed at 24 stops
    330 kwh estimated at 11 by minute stops

    So at home 100 x 6690 kwh / 8135 kwh = 82% making it into the car. Which seems a little low. Winter is coming.
  • edited October 2019
    @rxlawdude, ditto on solar and battery set up for self consumption.
    My 2 T's - S & 3 add about the same per month as you have experienced.
    Lucky for me, I have a good size solar system that keeps me off the grid except
    when returning excess power I've generated.
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