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Just Ordered 16.32kW w/2 Powerwalls
- Thread starter Southpasfan
- Start date
pdx_m3s
Active Member
2 Powerwalls won't be able to handle that much energy produced on a sunny day, so you'll have problems running off grid. See here:
New PowerWall install woes
It may work if you overpanel by a lot (meaning use a smaller inverter), but unless your inverted peak power is far under the panel spec power, like from significant shading for example, your setup is going to be a problem. Three Powerwalls is what you want to get.
New PowerWall install woes
It may work if you overpanel by a lot (meaning use a smaller inverter), but unless your inverted peak power is far under the panel spec power, like from significant shading for example, your setup is going to be a problem. Three Powerwalls is what you want to get.
This is very concerning, as I had just ordered the same layout as OP today (16kW + 2PW). Why would they even have that in the configuration tool of their store if it's not supported?
It depends on your configuration... If you use the Tesla design, it will more than likely recommend 3..
As per Combining Systems | Powerwall Support - "at least one Powerwall is required for each 7.6 kW AC of solar included in the backup circuit"
So, if you're doing a design with a smaller backup circuit, then, you can probably get away with it...
It’s supported, however your site visit will need to stress the amount of constant amperage you need to draw and at what voltage.
2pw = 60a constant @ 220v
3pw = 90a constant and so on as you add each PW.
Not sure what the draw has to do with the panels overpowering the Powerwalls. Basically the problem with 2 Powerwalls is that the power has nowhere to go when in off grid mode at full solar production. The system will shut down. Maybe if you're drawing constant power in an outage you can get away with it, but that seems like a really unstable and unpredictable setup.
Well, this is something else to figure out, but I was meeting with my electrician yesterday and he said the excess power goes into the ground. It makes sense because no matter how many Powerwalls you have they could be fully charged when you go off grid so it would not matter how many there are
The system will not shut down. The inverters handle the “problem” you’re creating and cycle on and off as needed. My system is much larger than my storage side.
the TEG handles the PW switching and you’ll never notice the difference.
the only reason to upgrade the amount of PW is to hold extra storage for EV charging during said blackout or amperage requirements.
Unless your electrician was joking, he doesn't know anything about this. Excess power never goes into the ground.
He wasn't joking, but he is a bit on the spectrum so I believe I asked the question incorrectly, which is not hard to do with electronics.
Anyway, posted the first draft layout on "Post your Layout."
It is interesting that some very basic questions elicit complex answers. The state of my understanding is now this.
1. The classic diagram, which one now gets with a Tesla or other modern system, shows electricity flowing from the panels to either the home, the grid, or the home/grid. If its nighttime there is nothing coming from the panels.
2. Throw in a Powerwall or two, and then you have another source of power to either grid or house.
3. If there is a power outage, the whole system shuts off, so that no power will be fed back into the grid to a downed line or something.
4. The answer to the follow up question ("you mean the system does not work in an outage? Seriously?) is that solar panes themselves can be, and are, "turned off" in some technical way if needed. I don't understand how this happens, but it does happen. Its not as if the panels keep on producing electricity and it "goes" somewhere.
5. Modern systems, especially ones with a Powerwall, operate to shut off the connection to the grid and then the panels are "allowed" to keep producing energy to the house or the Powerwall. This is kind of a key feature, obviously. I believe one could also do this manually, by switching ones self "off" the grid voluntarily. I have seen youtube videos to that effect.
1. Yep
2. Correct
3. This description is what happens without powerwalls.
4. Yes, the PV system without powerwalls (*or other battery storage) absolutely shuts down entirely in an outage. One of the most frustrating things you could possibly image is having a power outage of a few days, with solar panels on your roof you KNOW would power your home, but cant. This is to protect people working on the lines, because you would be generating power and possibly feeding it back into the grid, so people working on it could get electrocuted. Its wired to shut off, so correct, its not like the panels keep producing and the electricty "goes somewhere" The panels are off, in a power outage, if you dont have battery storage (just like everything else in your house at that time).
5. With battery storage (such as a powerwall) it has a computer (tesla calls it a gateway) that basically becomes the "hub" of your electrical system. Everything goes through it (over simplifying here, but this works). It decides which direction power is going (solar to home, solar to grid, powerwall to home, etc etc).
Addendum explanation:
Because this device is installed on "homeowner side" of the electrical system, on our side of the meter as it were, and is fully permitted, etc. in the case of a power outage, your home becomes its own "grid", with the solar panels taking the place of the regular grid, as it relates to electricity.
So, in this situation, your gateway prevents power from leaving your home. It sends power to either your home, and your batteries. If your batteries are full, the gateway forces the solar panels off (the concerns that people are talking about if you dont have enough storage to go with your PV system). The power doesnt "go to ground", in an outage, the power generated by your Solar either goes to your home to power your loads, goes to the powerwall to replinish the batteries, or gets shut off completely if there is nowhere for it to go.
In the system you are contemplating, with PV (solar) that size, and only 2 powerwalls, you definitely would have "nowhere for the solar to go" often, since there is so much power being theoretically produced. The batteries would fill up very fast, then force the solar off (it does this by raising the frequency).
If you really need all that power that is being generated by your PV system, then, in an outage, you would have a lot of it not being generated, because you have no place to store it. If I was buying a system that size, I would definitely get 3 powerwalls (its what tesla would recommend as well). Of course, you can choose not to backup some loads (if you have a pool, or hottub, or some other high draw load you dont want backed up, then you need less powerwalls).
Powerwalls are not the only battery storage, but in all cases, you need "something" between your home and the grid, if you have battery storage and are "grid tied" (connected to the grid), that enables you to create a micro grid of your home in an outage.
Yep, the hot tub is not getting backed up, nor I think, will the two EV chargers. The two Powerwalls can run the rest of the place either short or longer term 
.
it’s not often mentioned that not having a Powerwall means the system might not work at all in an outage!
. it’s not often mentioned that not having a Powerwall means the system might not work at all in an outage!
*EDITED*:
For clarification you mean *only* in the event of a power outage right? Under normal circumstance when batteries are full the gateway should be smart enough to the redirect excess capacity to the grid, as I would imagine?
The context of that comment is "in a power outage". It was all related to the paragraph above which was discussion "in this situation...." which was ment to convey "in a power outage".
Sorry if I wasnt clear about that. In a non power outage situation, the excess power would absolutely go to the grid (but in no case does it just "go to ground".
No problem.. im sitting here reading TMC while watching my wife play Animal Crossing.. shes all exited about the new swimming, etc (big video game household here, even though my wife and I are empty nesters now).
Rofl! I admire that! My new found cynicism has kept me from playing any of the newer games other than Overwatch. More power to you both.
Yep, the hot tub is not getting backed up, nor I think, will the two EV chargers. The two Powerwalls can run the rest of the place either short or longer term
it’s not often mentioned that not having a Powerwall means the system might not work at all in an outage!
Yeah, your right, it should be brought up more by the people selling PV systems, and its certainly not "might not" its "will not" lol. As far as running off grid, once you have everything installed, you can flip your main breaker and create your own microgrid (basically simulating an outage.
@BrettS has been running... err.. Testing, yeah thats it
his system since install and has gone days without being connected to the grid.
