So I ordered a M3 SR+ but I live in the "in-law" unit in SF. My landlord allows me to charge the vehicle on the condition that I pay for the electricity usage - fair enough. My commute is short with total driving of around 15-20 miles/day. I think I am just fine with 120V standard plug or even the 220V which I can plug in from the washer/dryer unit. I was thinking of getting this https://www.amazon.com/Poniie-PN200...0777H8MS8/ref=cm_cr_arp_d_product_top?ie=UTF8 to help find out how much electricity I use per day (or week/month). Would this unit be helpful? Can I overload the unit with 220V charging at 20amp as the max is only 3.5Kw. Thanks for all the help. I have been lurking for a while now.
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Measuring Kw usage at home charging my M3
- Thread starter TonyLSF
- Start date
Turlejay
Member
I'm not sure what you are asking but I don't think running 220v through the 110v adapter is a good idea.
I would highly recommend against using one of those pass-through pluggable meters. They are usually pretty cheaply made and are for either lower power or short term. There have been plenty of reports of the internals melting when they are running pretty full load charging a car for many continuous hours. Here are some threads mentioning that.
Wall meter to measure power usage?
Condo owner must pay for meter or unplug electric car
Charging rates, current draw, and efficiency data for 120V charging
110/120V Charging - some questions
There are some hardware solutions that can do this, like clamp-on ammeters, that go around a supply wire, so the current isn't passing directly through it, or installing a used traditional old electric meter with the big metal dial. But that seems like overkill for the small amount you need to know about. This is a case where I might recommend that it's a good use for one of the third party monitoring/logging applications like TeslaFi that can collect statistics using your own login to the car. The car has all of that information that can be collected. It's just not readily displayed on the screens easily, so an external logging program can collect that data for you automatically.
brucet999
Active Member
It is quite clear from looking at this gizmo that there is no way it will handle 240V. Its only pass-through plug is 120V as is its "heavy duty 14ga" extension cord. I don't see even a 240V 20A connector.
RFernatt
Solar/EV Owner/Enthusiast
I used a KillAWatt 120V meter to track my usage when I was charging my Leaf on L1. It was okay, but kind of a pain if the power went out, GFCI tripped, etc. And be careful about cheap units that may not stand up over time of continuous charging.
I have a JuiceBox EVSE that tracks all that now and can roll it up into a nice data export, but that would be a pricey option if you just want metering.
I have a JuiceBox EVSE that tracks all that now and can roll it up into a nice data export, but that would be a pricey option if you just want metering.
I just use Teslafi to track my charging kWh usage per day, week, month etc. If you know what the actual cost of electricity is and you plug that in teslafi, then it will even tell you how much you owe the guy for the month. It has a calendar feature that shows you every day so you can see your usage clearly.
seattlite2004
Active Member
What's the typical/average between what the car tells you it used vs what Teslafi says it put into the vehicle?
srs5694
Active Member
I agree that this is likely to be the easiest solution; however, TeslaFi costs $5/month or $50/year, so if you'll be in that living situation for several years, it could become a pricey solution if that's the only reason you have for using TeslaFi. Also, there are security and privacy concerns -- you're giving a third party access to your car's data, and that could be abused. Note that there are various third-party Tesla apps that provide features and data similar to what TeslaFi does. They've got similar security/privacy issues, but it's conceivable you'd prefer one of them. I use TeslaFi myself, so I can't provide you with a recommendation for a specific alternative; but it's worth researching them before you settle on one. Do not, though, try several such apps at once; they can interfere with the car's ability to go into sleep mode, which can result in unnecessarily high vampire drain.
If you prefer a more hardware-based solution, then I agree with @Rocky_H that an in-line plug-in 120v meter like the one you showed is probably not optimal. Clamp-on meters meant for long-term use are probably a better bet, but I don't know enough about them to make specific recommendations. If you decide to go for 240v charging and want a permanent or semi-permanent solution, and if you're using the existing 240v outlet for a dryer, then you'll want to add a Dryer Buddy to enable you to share the plug safely and easily. I just noticed that at least some Dryer Buddies include power meters. I haven't looked too closely, but if they provide cumulative use data, then that could be a good solution; however, this will work only for 240v charging. If you swap back and forth between 120v and 240v, you'll need a separate solution for the 120v charging.
Well its hard to tell exactly. The car shows you driving but not really phantom drain usage. Teslafi shows you what your charger put out and how much charge your car got. For instance today it was cold and not efficient so Teslafi shows my charger pulled 8.3 kWh from the wall to put 7.33 kWh into my battery so only 88.5% charge efficiency. It also shows me the total for that charge was $0.99. This month I am paying $0.12 per kWh so $0.12x8.3=$0.996. I love the stats it provides me.
srs5694
Active Member
The car's displays tend to emphasize driving use, rather than charging consumption. The driving use data omits preconditioning and vampire drain, so it can be pretty far off. The driving data also doesn't distinguish between home charging and charging elsewhere. I'm pretty sure that the charging screen does show a total kWh put into the battery, but I rarely check that -- rarely enough that I'm not even 100% sure of what data it shows.
Also, TeslaFi reports two numbers for charging: The into-the-car kWh and the into-the-battery kWh. The latter is recorded by the car, and the general opinion I've seen on this forum is that it should be quite accurate; however, for billing purposes, that number is not the most relevant one. For billing, the into-the-car number is more important, since there are losses/inefficiencies associated with charging. As I understand it, TeslaFi computes an into-the-car kWh number based on a minute-by-minute polling of the instantaneous kW reading. Thus, this number is slightly imprecise because the kW reading will fluctuate slightly over time, and the polling may miss a brief spike in use. Worse, if there's a data transmission error, some data will be lost and the number could be off by much more. That said, I've compared the into-the-car data as reported by TeslaFi to what my JuiceNet-equipped EVSE reports, and they match pretty closely, but not perfectly, presumably because of the polling and because of losses between the EVSE and the car. (Some power does go into heating up the cable, for instance.) My comparison was based on just a few charging sessions, though, so I may have gotten lucky or missed some huge glitches that could, in principle, be common.
As an example, here are what JuiceNet and TeslaFi report for my four most recent charging sessions at home:
Code:
Date JuiceNet Use TeslaFi Use TeslaFi To Battery
12/11 14.5 14.4 13.41
12/10 9.6 9.5 9.32
12/8 12.3 12.2 11.94
12/7 13.8 13.3 12.68FWIW, I noticed that the 12/7 session included two brief "spikes" in use after the main charge was complete. The first was shortly after the main session, and I think it was caused by the car recovering power lost to vampire drain shortly before it went to sleep. The second was at the very end of the session and was probably caused by my waking the car to unplug it; between waking and unplugging, it drew power for a few seconds. These spikes were picked up by JuiceNet, but not by TeslaFi, presumably because they were very brief and so didn't register on TeslaFi's polling. Even on that session, TeslaFi registered 96.4% of the power that JuiceNet said was used. If greater precision than that is required, then TeslaFi may not be the best choice; but if an underestimate of ~4% is OK, or if you and the landlord agree to an adjustment, then TeslaFi (or something else based on the Tesla API) should be fine.
Your JuiceBox idea would be the ideal solution. A little pricey but a great idea.
Those suggesting apps. Those would be inaccurate and don’t account for charging inefficiencies. Depends how exact landlord wants.
This is very cheap and accurate. But you need a little bit of know how on hooking it up. It could work on 120V or 240V. If on 240 you just double the reported numbers. You could install at the panel for the circuit used or adapt it at the plug. They make current loops that cheap for 120V. Not sure if they make them for 240 outlets.
This would not be load limited.
https://www.amazon.com/Current-Amperage-Voltmeter-Multimeter-Transformer/dp/B07JB9B2QL
Next to nothing. It only pings my car while it is awake and I have it set to go to sleep 1 minute after I park. It only pings tesla's servers to see if the car is awake when asleep so no drain there. I see virtually zero power draw this way. It actually helped me conserve power by finding my wifi was not allowing the car to go to sleep for 2 hours while coming home every day.
A bit off topic. My Wifi is enabled 100% and never delays sleeping enough to be noticed. This was true on Model 3 and X.
Something is wrong if your finding wifi causes 2 hour sleep delay. My guess is it could be related to using teslafi
It has nothing to do with teslafi. Its a common issue that everyone has but not everyone knows about unless they use an app like this. I have teslafi email me when it tries to go to sleep and when it actually does go to sleep. Every single time if connected to wifi it takes 2 hours like clockwork. If disconnected from wifi the car sleeps in 10 mins every time. Its obviously wifi and not teslafi.
I can go two 2 days and lose just 1 mile on either Model X or Model 3. If the car doesn't sleep it uses 1-2 miles an hour.
It sleeps like a baby within a couple minutes every time I park in the garage. Both Model 3 and X.
Believe me, I'd know if the car didn't sleep for 2 hours.
Try disabling teslafi (change password) and see what happens. Not saying it is absolutely that, there are other variables too. But, no, everyone does not have that problem.
Try putting the Tesla app's widget on your phone but don't open the app, just monitor it as it will show if the car is asleep right on the widget. As long as you don't open the app via the widget it won't interfere with your car going to sleep. Now watch when you come home from somewhere and make sure your car connects to wifi before getting out of the car. If the widget doesn't show the car falling asleep within 10 mins you do have the issue.
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