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2 vs 3 Powerwalls

Southpasfan

Member
Jun 2, 2019
461
587
Pasadena
Ended up adding the third Powerwall. Thanks for the input, y’all!
You will not only not regret it, you won’t even believe you considered not getting it. Last night my wife and I were chatting with someone and she mentioned giving someone the eGolf, when it gets too old. The first thing that went through my mind was “give it away? It’s got the equivalent of two powerwalls in that frame, I’ll cover it in plants and figure out how to connect it to the system before I give it away!” :)
 

holeydonut

Supporting Member
Supporting Member
Jun 27, 2020
2,120
1,503
East Bay NorCal
Yeah it's weird how 3 Powerwalls is like 1/3 a Model S in terms of battery capacity. These things are teeny but soooo damn expensive lol.

But for some reason the amount of headache to put the Powerwalls on the wall is like 10,000,000x worse than the effort it takes to park the car in the garage and charge it.

PS, I originally wanted 2 powerwalls, but ended up with 3 due to the large-scale SGIP. And now I wish I had 4. These things are the bomb (literally... since Santa Clara County thinks they're going to thermal runway into oblivion and burn the house down).
 

Novero

New Member
Jul 30, 2021
2
0
Los Angeles
My 16.3 kw Solar + 2 Powerwall installation is pending and almost done with permitting. With Tesla’s more favorable financing now, I’m considering adding a 3rd Powerwall. I know my home’s AC compressor is compatible with 2 Powerwalls. Is there any clear reason for me to add a 3rd Powerwall to the install? Our daily electricity usage varies between 60-90 kwh this summer depending on our AC use and how much my car needs to charge. We have a gas furnace so electricity usage will be lower in the winter, though we also have an electric dryer.

Also, our utility will be starting some fairly high time-of-use rates, especially between 4-8 pm, some time later this year.

Happy to get any input people can give. Thanks!
Keep in mind that all new powerwalls are the powerwall plus and will be increased by 50% with a firmware update soon
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,403
11,744
Riverside Co. CA
Keep in mind that all new powerwalls are the powerwall plus and will be increased by 50% with a firmware update soon

I am not quite sure what you are talking about, but storage is not increased 50%, and "all new powerwalls are powerwall+" is a false statement. Tesla absolutely still sells powerwall 2s.
 

Will792

Member
Oct 9, 2018
34
18
CT
I am not quite sure what you are talking about, but storage is not increased 50%, and "all new powerwalls are powerwall+" is a false statement. Tesla absolutely still sells powerwall 2s.
Technically he didn’t write that storage increased 50%. We do know that max current increased 50% in PW2+ and potentially the same change might be applied to the existing PW 2s.
 

h2ofun

Active Member
Aug 11, 2020
2,937
564
auburn, ca
Technically he didn’t write that storage increased 50%. We do know that max current increased 50% in PW2+ and potentially the same change might be applied to the existing PW 2s.
Instant or continuous? If continuous, not sure that would be possible with the existing 10 gauge, 30 amp wiring?

So are PW2+ being wired with 8 gauge, 40 amp breakers to the generation panel?
 

Vines

Active Member
Jul 20, 2018
2,051
2,379
Silicon Valley, CA
I have seen the post firmware update and it 100% does not increase capacity or continuous output. The firmware upgrade when deployed allows it to start large loads like AC compressors or pumps MUCH better.

Our installs since late last year have all been the newer units, all they are waiting for is that firmware.

I estimate it'll be "2 weeks."
 

Will792

Member
Oct 9, 2018
34
18
CT
Instant or continuous? If continuous, not sure that would be possible with the existing 10 gauge, 30 amp wiring?

So are PW2+ being wired with 8 gauge, 40 amp breakers to the generation panel?
I am almost sure that all Tesla installations use 90C 10AWG wire rated for 40A. If breaker is replaced with 40A everything should be compliant for wiring between generating combiner and PWs. 30A x 1.25 (continuous load factor) = 37.5A, next available breaker size 40A. It does not exceed wire rating in 310.15(B)(16) table.

It is a good point about breakers and possible violations of miscellaneous constraints and limits. I had to get a review of my system with utility company since aggregate wattage of PWs and PV exceeded 20KW. Electric company assumed max feed current of battery systems to be whatever was in the spec then.

The more I think about it the less likely I see a possibility of having this limit raised in the existing units through a firmware update.
 

Vines

Active Member
Jul 20, 2018
2,051
2,379
Silicon Valley, CA
Sorry but you cannot use the 90C column when determining ampacity at the end of a circuit.

If you are trying to derate a wire for fill factor or temperature, you may start at the rating given by 90C as long as the final number is not larger than the rating at 75C.

The rating at 75C is 35A. The breakers are rated at 75C, so that's as much as you can get out of a #10 copper wire in a normal 240v split phase residential service.
 

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