PowerWall tips for when grid is out!

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. :)


markbraukman | 9 juli 2019

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.

Tesla-David | 9 juli 2019

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.

Tesla-David | 11 juli 2019

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.

mrburke | 13 juli 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.

gregbrew | 16 juli 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.

Tesla-David | 17 juli 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.

r_p_rocha | 6 augusti 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.

brutschy | 6 augusti 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.

Tesla-David | 7 augusti 2019

@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.

Sjohnson1975 | 14 augusti 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.

DermMD | 17 augusti 2019

In the short-term, an easy solution Tesla could implement very quickly is to get a notification through the App when GRID goes down. I'm glad to experience that the Tesla powerwall take over when the grid goes out is so rapid that it is mostly imperceptible to me and I suspect most other people. Particularly when one is going on about life and not paying attention to the mundane.

Sjohnson1975 | 18 augusti 2019

I sometimes get a notification from the Tesla app when the grid is down and the powerwalls are running. But, it seems to take quite awhile for it to arrive. One time I got the text message from the power company that the power was out but the Tesla app never sent the notification.

sashton | 21 augusti 2019

To stop a car charge draining the PWs when the grid goes out I am afraid I do something slightly geeky. I check the GW every thirty seconds for its backup state. If the grid goes down I issue a command to the car charges to stop and scheduled charges and set a mode where the cars only charge when the batteries go over 80% SoC (from PV gain) and stop when they drop below 70%. (via their server API - Myenergi Zappi).

gregbrew | 21 augusti 2019

I recently found that Powerwalls will refuse to properly take over if the grid goes down while EVs are plugged in. My house lights pulsed as the two PWs tried to take over, saw an excessive current draw and shut down, only to try again over and over. According to the Tesla phone support tech, my PWs reported an instantaneous draw of 104A as they transitioned. Even though both EVs were full, they drew a bunch of current for a few minutes to top themselves off. (I've got three refrigerators trying to come back at the same time as two EVs.)

What "fixed" it was to unplug the EVs, switch off the PWs, and then switch them back on. In the future, while away from home, I'll leave both of my EV(s) plugged in with 1KW EVSEs instead of 3.3kW and 7kW EVSEs.

BTW, my experience with Tesla Energy phone support was as good as it gets. Short hold time, and a knowledgeable first-line tech that was able to access my PWs and tell me exactly what they did, and why. After reading all the negatives about Tesla Support here, I thought I'd throw them a little well-deserved love...

r_p_rocha | 21 augusti 2019

I believe the peak amperage of 1 PW is 29Amps (7kW) and the sustained amperage is 20 Amps (5kW). Given I have 3 PWs I could draw ~60 Amps for a continuous time, but if my 2 cars are charging (J1772) in the middle of the night and any extra load that kicks in (e.g. heatpumps) it could take the whole system down.

Tesla could easily solve this through automation, sending a stop charge command to the cars. For now I will pursue @sashton's solution above, with a small code running on Azure Functions and polling the PWs to find out status. If in back up state, then issue command to stop charging the car.

@tesla - this should be super easy for you to solve... !

r_p_rocha | 21 augusti 2019

I believe the peak amperage of 1 PW is 29Amps (7kW) and the sustained amperage is 20 Amps (5kW). Given I have 3 PWs I could draw ~60 Amps for a continuous time, but if my 2 cars are charging (J1772) in the middle of the night and any extra load that kicks in (e.g. heatpumps) it could take the whole system down.

Tesla could easily solve this through automation, sending a stop charge command to the cars. For now I will pursue @sashton's solution above, with a small code running on Azure Functions and polling the PWs to find out status. If in back up state, then issue command to stop charging the car.

@tesla - this should be super easy for you to solve... !

gregbrew | 22 augusti 2019

You do realize that there are many other EV makers out there? Tesla sending a "stop command" to the cars isn't going to work for a Bolt, a Volt or a Leaf.

sashton | 22 augusti 2019

@gregbrew I think he's suggesting Tesla can kill a charging for a Tesla charger in the event of a power cut.

Of course, for other cars or chargers one would have to roll ones own solution.

The trigger would be to check /api/system_status/grid_status and any response onther than {"grid_status":"SystemGridConnected"} would indicate a backup situation

I use Myenergi Zappi EVSE and the method to stop all scheduled charge sessions and ensure any manual charges cease is to submit:
To only permit charging when there is export (which will not happen while islanded) and:-
To stop any timed charge sessions

where xxxxxxxx is the serial# of the EVSE in question

sashton | 22 augusti 2019

BTW I am not espousing the use of the Myenergi EVSE with Tesla cars.
The M3 has only recently arrived in the UK and currently there are compatibility issues with these models which appear to stem from the car.
There are no issues with any other EVs: Chevrolet, Jaguar (recent firmware), Hyundai, VW, BMW etc. (as far as I am aware).

mikemillar | 27 augusti 2019

If you have the new Gateway 2 backup gateway the answer is to have the car charger wired in on the non-backup side as mine is. Then in the event of a power outage the car charger doesn't charge and suck all the juice out of the Powerwall, which only powers the backup side, normally the home loads. Unless, of course , you have a multiple Powerwall installation with enough capacity to charge the car as well as provide the home loads in the middle of the night.

gregbrew | 31 augusti 2019

Mike, Your technique won't work if the PWs back up the entire house, and the charger is on a sub-panel, as mine is.

Joecreek | 6 mars 2020

I'm extremely frustrated. We were not warned about two serious shortcomings with the new powerwalls until AFTER installation and billing.

First, there’s no function that alerts us that the grid power is down. We slept through a long outage, and awoke to see that we’d lost about 45% of power walls' capacity! This is a serious design defect, which could be easily solved by adding one lousy receptacle that’s not protected by powerwalls, and gives off a shrill alarm when power goes out. They are readily available, and VERY cheap, eg:

What good is a bunch of powerwalls which go dead because you don’t disconnect large loads, due to not knowing grid is down? Not much.

Second issue. I’ve wriggled down a couple of dozen bottomless rabbit holes trying to figure out why the powerwalls, connected to my solar system, ARE NOT ALLOWED to be recharged from the grid. One Tesla video says they can be, if the power company allows it. Our power does allow it-sees no reason not to. Yet, Tesla refuses.

After our 40 hour blackout a month or so back, and having lost 45% of the charge while sleeping, the power walls went to essentially zero charge in a small number of hours, because we left a freezer and fridge running.

Guess what? In this climate, this time of year, it took just under a week to recharge the power walls using only solar.

Tell you what; if I’d known these glitches before paying for the power walls, I don’t think I’d have paid out almost $20,000, after 30% tax credit.

Is there anyone here who has any suggestions? I’ve now given up, but may see if Tesla will AT LEAST add a single receptacle that would trigger a lost power alarm. If they won’t, I’ve had good success with other companies using (cheap!) Small Claims Court.

If Tesla corrects these two problems, I will become an extremely satisfied customer, guaranteed!

Joecreek | 6 mars 2020

Tesla David, hell, i presume you’re the same gent I’ve spoken with before.

Your advice, above, “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”

All excellent advice; however you left out an extremely critical part of the equation. If the grid power goes down, you're in danger of losing a huge percentage of your Powerwalll's charge, because you won’t be aware that the grid is down. This happened to me once already, to my extreme frustration.

There should be an easy way to wire in a single receptacle, upstream of the powerwalls, which will let off a loud, or a deafening* scream to let powerwalls owners know to shut off all unnecessary large loads. In fact, a main Director of Pacific Power and Light was the one who made this suggestion to me, about an hour ago in our phone call.

Something better happen fairly soon, while I’m still (barely) maintaining my cool.

Thanks, Dave. Here’s a url showing the louder (120 dB) power out warning gizmo. There are many varieties available on the web.

bp | 7 mars 2020

The Tesla app (at least on Android) is supposed to provide a notification when the system goes on or off grid power. This is enabled in the Tesla app settings under Notifications (as long as the Tesla app is allowed to provide notifications under the Android Apps settings).

The federal solar tax credit provided the 30% credit for PowerWalls only if the PowerWalls are powered only from the solar panels (except in Storm Mode).

Evidently Tesla is enforcing this by not allowing PowerWalls (installed with solar) by not allowing the PowerWalls to be charged from the grid.

It is possible to purchase PowerWalls that will charge from the grid. In that configuration the warranty changes.

Patrick | 7 mars 2020

Interesting conversation. As a new PW owner, after activation I was reminded of how quickly Model 3 charging will deplete our three PWs when charging at the full 7.5 kW charge setting. Charging the car with PW energy does not seem like a wise choice for several reasons.

Haven’t spent a lot of time thinking about creative options yet. My first thought was simply to charge the car during days with strong 9-10 kW solar generation when plenty of free energy is available. Next thought was to rig the 14-50 charging outlet to pull juice directly from the utility grid vs our microgrid - this option enables any-time charging with no impact on PW capacity but requires paying for the charging energy. Still noodling on this topic...

Regardless of the car charging approach I like the idea of installing an alerting system for notifications of utility grid failures - thanks for sharing. Numerous ways to handle this as long as a non-microgrid power outlet/source is available as stated above. In our case we’ll probably try using SmartThings notifications which can provide alerts while either onsite or via mobile device.

Patrick | 7 mars 2020

bp - thanks for the reminder that Tesla app should provide notifications of grid failures. Can’t recall if we tested that function but will verify.

Please say more about buying PWs that can charge from the grid here in the US. Are Different models of PW available?

bp | 8 mars 2020

On Tesla's PowerWall page, you can configure the order to be for a system with or without solar panels. If you select with solar - the price reflects the 26% federal tax credit.

Without solar, you don't get the tax credit. Tesla would configure the PowerWall to allow grid charging, and should also note in their system that the PowerWall would use the grid charging warranty, which doesn't cover unlimited charging.

When we were planning our 15.4 KW/4 PW system last year, one of the options we considered was 4 KW of panels and 4 PowerWalls, planning to charge the PowerWalls from the grid overnight using a Free Nights plan (the terms of those plans don't appear to preclude use with solar panels/battery storage). We ruled that out when we discovered we wouldn't be able to get the 30% tax credit (which is why we included the 4 KW of panels).

If you're willing to forego the federal tax credit, it's possible you could get Tesla to configure your system for grid charging.

AOSTV | 8 mars 2020

Really appreciate you sharing this blog post.Much thanks again. Fantastic and waiting for more info | 15 mars 2020

@Joecreek "there’s no function that alerts us that the grid power is down."

Yes, there is - in the app, go to notifications, Energy, and toggle "Power Outage".

"..connected to my solar system, ARE NOT ALLOWED to be recharged from the grid"

This is an issue with your local power company. There are locations (UK?) that allow this, but many (all?) locations in the US do not allow this. Tesla is just following the law. It's not a technical issue, as they do allow this function in some countries.

The concern/scam by the electric companies is you'll charge at the lowest power rate and then use your battery power during peak times, depriving them of money. Your fight is with the electric companies, not Tesla. Good luck with that!

As for going to court to add features Tesla never offered or promised, I don't see a good outcome for you. I'd like my car to go 700 miles on a 5 minute charge. Doubt I can sue to get them to add that to my car.

dhalbasch | 17 mars 2020

My app has neither "Energy" nor "Power Outage" in "Notifications" or anywhere else I can find. Located in California

gregbrew | 17 mars 2020

Tap on the little gear (settings) in the upper left corner of the app's main screen. Below "Inbox" and Loot Box" is "Notifications". Tap on "Notifications", then tap on the little circle to the right of "Power Outage", to make the little check mark appear. This will enable the app itself to send you notifications.

Make certain that notifications is enabled for the Tesla app in the phone's app settings, too.

mikenorthrup | 18 mars 2020

Very helpful discussion. I just had a single Powerwall 2 installed yesterday with whole house protection and my Tesla solar panels are currently generating 3.1 KW and are charging up the wall @2.8KW and supplying my house power @.3KW. I've had my Model 3 charging up at night (after 9PM for lower rates). I set the Powerwall app to self-powered with a 50% reserve for Power Outages. I use the Tesla mobile charger on a 14-50 outlet, charging up at 32A.

Several questions--at 9:00PM with no solar generation, will the Powerwall charge up my car and meet my house power requirements (about .4KW continuous with and occasion spurt for a microwave or a blender)? Is my 32A setting too high for my single Powerwall and, if so, will some circuit breaker "trip" and my house be switched over to grid power? When the battery depletes to 50% I assume that I will be kicked over to the grid.

Thanks for the great discussion.

bp | 19 mars 2020

Realistically, with a single PowerWall, you're not going to be able to charge an EV very much.

A single PowerWall can store about 14 KWh of energy (at a 100% charge) and can discharge 5 KW of power continuously.

Model 3 battery packs range in size from 50 KWh to 75 KWh.

If nothing else is running off the PowerWall, you should be able to charge up to 20A from a 14-50 outlet. Anything above that would exceed the output of a single PowerWall.

If you set a 50% reserve, if the PowerWall starts at 100%, you'll only get 7KWh of charge.

Our system has 4 PowerWalls. We have an S 100D and X 100D, and do not plan to use our PowerWalls for EV charging unless grid power is off (after a hurricane) or we have multiple days of full sun and we're generating more power than our house is using (we don't have a solar buyback plan).j

With Mike's configuration, what will likely happen is that once the Model 3 starts charging, the PowerWall will be depleted in 85 minutes. If the Model 3 is using more than 20A, the extra power will come from the grid. And once the PowerWall hits 50%, all of the power will be coming from the grid.

Might be worthwhile to lower the reserve % to 20, so more power is stored in the PowerWall during the day, and available for EV charging - but even then, a single PowerWall will provide only limited charging for an EV.

dhalbasch | 19 mars 2020

What part of "My app has neither "Energy" nor "Power Outage" in "Notifications" or anywhere else I can find". did you not understand?

Tesla-David | 19 mars 2020

@dhalbasch from your Tesla app depress the Home Energy Gateway button on left side. That will take you to the Settings page, where you will see "Notifications" After depressing Notifications you should see two options "Vehicle" and "Energy". If you depress Energy you will be directed to Power Outage, and depress that to engage notification on Power Outages.

Tesla-David | 19 mars 2020

@mikenorthrup, I agree with @bp with one PW2 you will not be able to able to fully charge your M3 off your battery especially with your reserve set at 50%. We have two PW2's and only charge our MS and M3 during peak solar with reserve set at 25% so as not to drain the battery and then we only charge at 25A so as to stay within the limits of our solar production and not drain the battery. We could charge at higher amperage but that would trigger grid draws which we want to avoid.

gregbrew | 19 mars 2020

You must be using an iPhone app. The Android UI seems quite different.

I fully expect dhalbasch to respond with yet another snarky comment to the very people trying to help him. He (she?) won't be getting any more help from me...

Jones | 22 mars 2020

-dhalbasch - if you are using IOS app...
1 - touch the gear icon upper left
2 - touch notifications
3 - touch energy (my app shows vehicle & energy since I also have M3)
4 - enable "power Outage"
If yours is a new install, many of these features take a couple of days to be activated - I believe it was about 4 or 5 days after install that I saw some of these options.

mikenorthrup | 22 mars 2020

@Jones I have the iOS App and don't have the "Power Outage" choice. But, since my Powerwall was only installed on 3/17, I'll give it a few more days. It took a few days for the "Edit Price Schedule" and for the "Storm Watch"slider and graphics to show up on the app.

Thanks for the post.

Jones | 23 mars 2020

FYI - I am on firmware 1.45.1 for the powerwalls and 3.10.4 for the app

megandarr | 24 juni 2020

Kroger has designed a very good way for customers to voice out their opinions. The krogerfeedback online survey serves for gathering timely, honest and objective customer feedback regarding the shopping experience.

sonoboy | 26 juni 2020

dhalbasch did you figure it out? I'm on an android using software version 1.47.0 and also having troubles. Seems like I remember setting up notifications when doing storm watch set-up....

sonoboy | 26 juni 2020

So I just got off the phone with Tesla powerwall support regarding the lack of a notification setting. He did say my version was the updated one and they said there was a glitch with this setting availabilty since the last update. A ticket is opened and i'm added to the ongoing list.

gregbrew | 27 juni 2020

This is yet another case of "if it ain't broke, don't fix it!"

Why, oh why can't I control the firmware in devices that I paid nearly twenty grand for? All I ask for is an option to turn off automatic updates. I don't give a rat's patootie if 1.46 didn't work properly in Japan (or 1.45 in Barbados or New Caledonia). It worked great for me, until Tesla "fixed it" for those other locations many thousands of miles away, with requirements that are different than mine.

/end rant

sonoboy | 7 juli 2020

"bump" Any android users get their notification setting back?

sonoboy | 14 juli 2020


sonoboy | 20 juli 2020

I see the software fix for notifications/power outage is now operational.. Version 1.47.0/ 3.10.7