Energy Products

when grid power is out...

when the grip power goes out, should the powerwall system be able to use solar energy to charge / run still?
on my app, it seem solar just stopped and only the powerwall is powering my house at the moment.



  • edited September 2019
    If the grid goes out during the day (when the sun is up, and the panels have the potential to produce power), the panels are supposed to recharge the Powerwall. When the Powerwall is fully charged, however, the panels have nowhere to send the excess power they are producing, so they will shut down until the Powerwall charge drops to a level where they can start recharging it again. That's the way others have reported it works for them.
  • edited November -1
    @Noam got it right. That is exactly the way our 2 PW2’s work for us.
  • edited September 2019
    If the solar output is higher than the house load, excess should go to the Powerwalls. Otherwise, solar output will go to the house, and the Powerwall will supplement it.

    If that isn't happening, call your installer's service dept.
  • edited September 2019
    Just had my PowerWall install complete a few days ago. Unfortunately my system DOES NOT work that way. App shows battery discharging while solar should be (and was before power out) generating 4-5x of what the house is generating. Battery continues to discharge. Happens in Backup-only, Self-powered, and Advanced modes. @Tesla-DAvid, @jrweiss98020, was there some config you had to setup to get this to work?
  • edited September 2019
    I have the same issue on the app. Power goes out, and the app only showing battery powering the house. nothing from solar. however, I am not sure if it's an app issue or a Powerwall issue.
    power was out from 10am to 840pm, and the Powerwall was still at 97% when I got home around 6pm.
    So the solar could be charging the Powerwall, just the app is not showing it?
  • edited September 2019
    @T-EdisonFTW, I had our PW2 installation 15 months ago, and have been operating exclusively in self powered mode. I did not have special config to get or PW2’s working. The solar always charges up the PW2’s after house loads are satisfied. In self powered mode this year we have not drawn any grid energy since mid-February. We experienced one power outage earlier this month, but it only lasted 5 minutes with no interruption in power with the PW2’s. We are exporting on average 60 percent of our solar energy back to grid over what we’ve erate to run our all electric home and charge both Tesla’s (MS and M3). Absolutely amazing product IMHO.

    I would discuss your issues with Tesla-Energy to fix the apparent problem with your current setup.
  • edited September 2019
    I've had a ticket open with them since 8/15/19, and no resolution yet.
    Tried calling one day and gave up after 3 hrs on hold for a rep.
    (this is for a different issue, app showing power being drawn at 2x the rate vs pge chart)
  • edited September 2019
    TEdison, I did not have to configure my system; it just worked!

    OTOH, I did test it for a couple days between the time install was completed and Net meter was installed by electric utility company. To do this, I opened the circuit breaker between the Gateway and grid supply, simulating a grid outage. Solar powered house and recharged Powerwall as expected.

    For troubleshooting purposes, you could do the same thing when the installer's troubleshooter is at the house. Open the main supply breaker outside the Gateway on a sunny day, and see what happens. To determine if it is the app or the installation, keep the breaker open long enough, and run a high enough load (car charger, oven and/or dryer) to ensure the Powerwall should drain a reasonable amount (3-5%?). Then reduce the load and see if the solar start recharging the Powerwall. Even if the app doesn't show the connection correctly, it sholud show the increasing charge level.
  • edited September 2019
    We had the same issue when our PowerWall was first installed and required an update.
    I contacted the installed who worked with Tesla to get it going. Also to note that during troubleshooting, the Tesla support tech mentioned that the battery had to reach a certain temperature before taking a charging, while the grid power was out. Not sure if that was part of what was going on, my initial test was in the morning but there was solar production coming from the roof or if it was just a flux capacitor type of answer.
    They also mentioned that after the batter reached above 88% (or some number like that) it would send a signal to shut solar production for safety (since there was no where to send that excess generation)
  • edited October 2019
    Couple of things to note to the OP. If the PV system is too large, it can't pair to the backup side of the gateway. The ratio I believe is 7600watt inverter/Powerwall. Even so, it the output excceds 5kW above house load, the gateway will shut down the inverter. That is the max charge rate, and most inverters can't throttle/curtail their output to match. So if that ratio is exceeded, the installer may have installed PV on the line side of the gateway which would work while the grid is on, but PV would go down with the grid. The next thing is make sure you test off grid mode for several minutes. Often the inverter will turn off when the grid goes down, then test the voltage before waking up again and operating. So give it time to do that. If the battery is too full, it will not want to charge and will shut the inverter down. So also test it out until the battery drops 10% or so. If it still isn't waking up, powering the home, and/or charging the battery, then you should check with the installer.
  • edited October 2019
    During grid outages, your Powerwall (PW) takes over, and the Tesla Energy Gateway (TEG) disconnects from the grid, while carefully monitoring it to see if it's come back and is stable. While the grid is out, it's up to the *very intelligent* TEG to manage power flows.

    During an outage, the TEG polls the PWs to see if they are full. If they are not, it allows the PV to function normally to power the house, and if there's excess from that, the TEG directs that excess power to recharge the PWs.

    Let me digress for a moment. Normal grid frequency is stable at 60Hz, and is tightly regulated plus or minus about .5Hz. Many electrical devices depend on that tight regulation to function properly, like clocks and motors, and importantly, *your solar inverter*. Your solar inverter is designed to shut down if the frequency it sees varies much from that 60Hz value. IIRC, it will shut off at anything below 58Hz or above 62Hz., to protect utility workers from the power your system produces during an outage. It's called "Islanding". Now, back to our regularly scheduled programming.

    When the PWs are full, and the sun is still providing power to the PV. The TEG learns (through the previously mentioned polling) that the PWs are full, and sees that the PV is providing more power than the house needs. That excess power (and maybe a *lot* of it) needs to go somewhere, but there's nowhere for it to go, because the grid is disconnected. The TEG handles this by simply shutting down the PV via the inverter. When the TEG wants to shut off the inverter, it signals the PWs to *change their output frequency* from the nominal 60Hz to 62.5Hz. The inverter sees this 62.5Hz on the house wiring as a "grid out-of-frequency" problem and *shuts itself off*. This stops excess PV power from being dumped into the house circuits, in fact, it stops *any* PV power from being dumped into the house, and the PWs continue to power the house at 62.5Hz. Once the PWs are below a certain "fullness", the TEG directs the PWs to change their frequency back to 60Hz, and the inverter is happy again, so it lets PV power back in, and the TEG directs it to the PWs to charge them back up. Once the PWs are full, the cycle repeats until the sun goes down, or until the grid comes back up.


    During a grid outage, as the TEG cycles power frquency to and fro, and turns the inverter on and off, the house power is acting a little wonky. It's not uncommon for Uninterruptable Power Supplies (among other things) to be driven nuts by this switching. The reason that the timing seems random is because, *is* pretty random. The time it takes the house to deplete the PWs below some threshold (I don't know what it its) is dependent on often varying house loads, and the time it takes the PV to recharge the PWs is going to depend on the sun and current weather etc..

    Some customers had good luck contacting Tesla to have the PW output frequency tightened up a bit on older PWs, yet still is enough out of the 60Hz nominal spec to shut off the inverter in a grid outage...BUT, if I'm not mistaken, that frequency tightening was already incorporated into one of the more recent PW firmware updates. Unfortunately, all of these house power shenanigans may be too much for some devices to handle, and observing it operating seems like it's totally random and bizarre. I think Tesla has already done what they can to lessen the impact.

    BTW, there are a couple other threads that talk about the frequency issues. That's where I got most of my information.

    I love thus forum!
  • edited October 2019
    Circling back to this. First off, @gregbrew, great overview! I haven't measured the frequency generated by the powerwall, but was wondering how my microinverters on my panels could all be shut off.
    Now that my powerwall gas gone through the first Great PG&E California Power Shutoff, I can confirm it operates as expected. Powerwall powers the house until it gets down to ~70-75%, then recharges off solar. This cycle repeats until sundown. Was able to maintain house power for the 3 days we were shutoff, just as I had hoped. I was thrown off when testing a synthetic power out event as the solar wasn't kicking in, but probably hadn't let the batteries run down far enough.
  • Thanks for this thread... late to the game. I have just started testing my system (solar roof with two PWs), and I am definitely observing this behavior. When the frequency is raised, it causes my consumer grade APC UPS to think it doesn't have power (a beefier commercial grade APC UPS doesn't have an issue). I think this is horrible behavior. I would expect the Tesla load center to deliver 120V / 60Hz AC to my house regardless of what is going on behind the green curtain. The fact that I even need a UPS at all bothers me, but it's the only way to keep sensitive equipment (computers, Smart TVs, DVRs) from rebooting during the brief voltage dip that happens when the grid goes out --- and comes back. And knowing that when the grid is out, my load is low, the sun is shining and the batteries are full -- my clocks are going to drift fast -- not nice. Finally, disabling the inverters when the batteries are full and the grid is out, this drains and fills the battery repeatedly during the daytime causing extra wear as well as wastes the perfectly good PV output that could be powering the house. Can someone explain to me why the inverter can't discharge extra energy to ground? How about Tesla providing a device to consume the excess PV output that the house can't handle (maybe a high wattage heater that vents off the roof)? So I should run every appliance in my house to avoid this problem when it happens? (That's a joke in case there's any doubt.)

    Draining and filling the batteries, flipping the inverters on and off and mucking with the frequency sucks. There's got to be a better way. Also, my utility grid supplies about 121-122VAC but the PWs only supply about 117-118VAC. That doesn't seem to cause any grief like the frequency shift does, but still... I got this system because I want to be off grid as much as possible and have nice 120V/60Hz output to my home without worrying about where it's coming from.
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