Energy Products

PowerWall tips for when grid is out!


I have 3 PW2 being installed this week and I should be online tomorrow. :)

In my installation, I opted for wholehouse protection and the PWs should be more than enough for 12 hrs+ without any compromise on my appliances and heatpump.

Question: For scenarios where the cars are plugged in and utility power goes out, is the Tesla App smart to trigger a command to the cars to stop the charging process? I certainly could do it manually, but thinking on scenarios when there is no one home.

If answer is no, I have sketched a little system already to solve for this (a sensor + app on raspberry pi that will trigger a stop charge command to the cars)... but I really would like to avoid geeking out on this one. :)



  • edited November -1
    I don't think so. I've not had a power outage when my MS is charging. When I have lost utility power, the PWs kick in. I would think that if my MS was charging at that time, it would drain the PWs and then all would go dark.
  • edited November -1
    The Tesla app allows us to stop or initiate charging on our MS and M3 easily to manage our 2 PW2’s integrated with our 13.2 kWh solar PV system. We operate in self powered mode with our backup set at 25 percent, and have been sel sufficient since mid February with our setup, not utilizing any grid energy. We try to time our Tesla charging when we have full solar so as not to drain the batteries, and usually stagger charging of our MS and M3.
  • edited November -1
    I meant to add in response to OP's question, the Tesla app will not stop your EV charging when the power goes off, but you can do so easily from the Tesla app. Obviously if the power goes off you want to turn off as many energy draining applications as possible to preserve the PW2's for essential stuff. I summarized above how we stagger our Tesla charging when the sun is out to maximize the efficiency of the PW2's.
  • edited July 2019
    Question from someone who does not have the system configured yet. (Waiting for Tesla to get back to me.)

    While two PWs are enough to handle my houses total electrical load, it likely that charging my car are 40 amps could overload the 60amps that I believe the two PW can produce when I factor in other household loads.

    While, I am happy to manage my loads manually, will I be required to put the charging circuit on a separate panel that is not backed up from the PWs ?

    Thanks in advance.
  • edited July 2019
    When the grid goes out, flip the Main breaker in your electrical panel, to isolate your system from the grid. Grids are notoriously "dirty" in outages, and can drive the TEG bonkers. It happened to mine.

    Once you're sure the grid is back up (and clean), restore the main breaker.
  • edited July 2019
    @mrburke responding to your question about whether 2 PW2’s will be able to handle your home loads and Tesla charging. For us the answer is yes, but we limit the charging to 25 Amps to keep the batteries from draining down, and stagger our charging for both Tesla’s. This has worked for us over the past 13 months. See my summary above. We could manage a higher charge rate, but that would trigger grid draws, which we are trying to avoid.
  • edited August 2019
    Thanks Tesla-David and team. The tips above certainly work well when we are in the house and can notice that power is out and stop changing of our cars through the app. What I would like to do is to automate the process, in case it all happens in the middle of the night while we sleep. The scenario is that cars are charging and then Utility power goes out. The PWs will either pick it up and be drained really fast or their breakers will open the circuit and I will lose battery power into the house (defeating the whole purpose of having PWs to start with). I could and should have installed the car chargers in a separate circuit (not covered by the PWs), but that's water under the bridge now.

    PSE (where I live) does send a notification to the phone in case of power outage and it also sends an e-mail... I can write an app to trigger a STOP CHARGE command to the cars as soon as I get the notification... but my main concern is to know how long it takes for PSE to find out about the outage...

    Anyway, Tesla could easily solve this with... so here is a feature request to them.
  • edited August 2019
    Tesla-David -- How do you limit the charging to 25 Amps? My Model 3 is set to charge at 48 Amps, and I can find no way to change that.
  • edited November -1
    @brutschy, In your M3 you can easily specify your charging amperage. For our MS, with our 100A HPWC and a second onboard charger, I used to charge up to 80A, but limit it to 25A now as I mentioned, because of the PW2's. Yes the default for charging in the M3 is 48A, but you can easily specify whatever charging Amperage you want to charge at as well as the time you want to charge from your car.

    @r_p_rocha, with our setup, we clearly specify the time to charge our two Tesla's so that they do not charge during the middle of the night and thereby drain down our 2-PW2's. I currently stager both cars charging, charging our MS at 9:30 a.m. and our M3 at 10:30 a.m. This has worked well for us.
  • edited August 2019
    It would be great if Tesla could make a feature that automatically stops the car from charging when the powerwalls turn on.

    I have 3 powerwalls and if my car is charging and the grid goes down I would like it to just stop until the grid is restored.

    Hopefully they are working on this.
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