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Partial vs. Whole Home Backup?

h2ofun

Active Member
Aug 11, 2020
2,472
423
auburn, ca
Many of the safeguards are just that. Something to take control for the unforeseen situations where safety is a concern. In my case I am purposefully taking advantage of that feature operationally, which probably was not as designed.

Tesla and I negotiated this up front and had a big discussion about it at a lot of different levels and persons. They may not be so willing to do this today but I do know of a number of other installations that have the same type of issue.
Seems if one had to put in enough PW's to never have them trip would be so costly that many may have had to pass on batteries?
 

holeydonut

Supporting Member
Jun 27, 2020
1,517
892
East Bay NorCal
A simple solution might to have the grid control power to the thermostat circuit. Depending on logistic that may be the complexity you are referring to.

Yeah, if you can figure out how to get it to work, the Tesla Energy Gateway can shed a load during a power outage, so a circuit that is on the backup loads side (such as an AC condenser) can be bypassed where it won't turn on unless the homeowner intervenes.

Powerwall Automated Load Shedding?

But as far as I'm aware, this type of load shedding feature doesn't actually work yet and Tesla needs to update the firmware to hopefully unlock the functionality.
 
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aesculus

Still Trying to Figure This All Out
May 31, 2015
4,436
2,514
Northern California
Yeah, if you can figure out how to get it to work, the Tesla Energy Gateway can shed a load during a power outage, so a circuit that is on the backup loads side (such as an AC condenser) can be bypassed where it won't turn on unless the homeowner intervenes.

Powerwall Automated Load Shedding?

But as far as I'm aware, this type of load shedding feature doesn't actually work yet and Tesla needs to update the firmware to hopefully unlock the functionality.
Thanks for this thread link. I will look at it more later.

My environment is really complex but I might tie into that thread and see what others suggest.
 

aesculus

Still Trying to Figure This All Out
May 31, 2015
4,436
2,514
Northern California
A simple solution might to have the grid control power to the thermostat circuit. Depending on logistic that may be the complexity you are referring to.
I don't want to take away from this thread but I thought I had a solution such as this that is used in hotel rooms but it turned out not to be useful in my case.
 
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aesculus

Still Trying to Figure This All Out
May 31, 2015
4,436
2,514
Northern California
Seems if one had to put in enough PW's to never have them trip would be so costly that many may have had to pass on batteries?
Depends a lot on your type of A/C or heat pumps (and other loads of course). I calced mine to be most functional during PSPS events. My heat pumps are so old that I would gain more value on getting new heat pumps vs adding more Powerwalls. Now waiting for Elon to create the next generation heat pump. :D

Elon Musk Is Attempting to Revolutionize HVAC Systems
 
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d21mike

Active Member
Aug 28, 2017
1,097
722
Torrance, CA 90503
I have whole home backup with 12k solar and 2 power walls. Tesla was my installer. I was not sure what they would do but I said I would like whole home backup (I think) or they said you can have whole home and they just did it.

I have 200a power to my house.

I have 1 AC and they installed a slow start (not sure of name) so that the AC does not pull a lot of power during startup.
I have 2 Tesla's sharing 1 60a circuits. This was my main concern because it will empty my battery backup pretty quickly. I was hoping Tesla would resolve this before it became a problem for me and they did. I can set how much it will pull during a power failure.

I have not had many power outages since my install about 1 year ago. So, not sure if I will have problems in the future.

BUT, I love it. Works great.
 
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Electrph

Member
Aug 29, 2019
392
233
Central California
I have whole home backup with 12k solar and 2 power walls. Tesla was my installer. I was not sure what they would do but I said I would like whole home backup (I think) or they said you can have whole home and they just did it.



I have 200a power to my house.

I have 1 AC and they installed a slow start (not sure of name) so that the AC does not pull a lot of power during startup.
I have 1 Tesla's sharing 1 60a circuits. This was my main concern because it will empty my battery backup pretty quickly. I was hoping Tesla would resolve this before it became a problem for me and they did. I can set how much it will pull during a power failure.

I have not had many power outages since my install about 1 year ago. So, not sure if I will have problems in the future.

BUT, I love it. Works great.

i have pretty much same but with 8k solar .. 2 pw ac soft start model 3 .. no issues / no "tripping" power walls when testing AC in winter .. just have to be reasonable when you charge car .. if tesla connector will adjust from up to 44amps down to 36amps (in my case ) based on amount / and pv energy .. house load ... automatically .. nothing to set
 
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Notadog

Member
Jan 26, 2021
40
3
SF Bay Area
OP here, thanks for the replies again. So it does seem like the design is arbitrary and there is no hard criteria where they will deny a whole home backup request.

In my original application, I specified that I did not own an AC or EV (since I do not) so those loads should not have been taken into consideration. On Tesla's own website, they specify that for scroll-type ACs, 2 Powerwalls are sufficient as long as the LRA was <139 (What Does Powerwall Back Up | Tesla Support). Therefore, for a standard home without AC or EV, I do not see the reasoning behind recommending 3 Powerwalls. I will email my rep to ask for the design details behind that decision.

  • For those who have 2 Powerwalls, was the AC slow-start part of the Tesla install?
  • For those with Partial Home backup, at what stage do you get to specify which circuits go in the backup subpanel, and which circuits will be left in the main panel? Specifying which combination of circuits can be backed up and which ones cannot would also have helped me arrive at a decision but Tesla did not specify.
 

aesculus

Still Trying to Figure This All Out
May 31, 2015
4,436
2,514
Northern California
For those with Partial Home backup, at what stage do you get to specify which circuits go in the backup subpanel, and which circuits will be left in the main panel? Specifying which combination of circuits can be backed up and which ones cannot would also have helped me arrive at a decision but Tesla did not specify.
From my personal experience: They will give you a quote and design. Then an onsite person will come out to review the plans with you and make recommendations to the design team. Then you can negotiate/change the design. Then when the installers come out you may even get something slightly different.
 

d21mike

Active Member
Aug 28, 2017
1,097
722
Torrance, CA 90503
OP here, thanks for the replies again. So it does seem like the design is arbitrary and there is no hard criteria where they will deny a whole home backup request.

In my original application, I specified that I did not own an AC or EV (since I do not) so those loads should not have been taken into consideration. On Tesla's own website, they specify that for scroll-type ACs, 2 Powerwalls are sufficient as long as the LRA was <139 (What Does Powerwall Back Up | Tesla Support). Therefore, for a standard home without AC or EV, I do not see the reasoning behind recommending 3 Powerwalls. I will email my rep to ask for the design details behind that decision.

  • For those who have 2 Powerwalls, was the AC slow-start part of the Tesla install?
  • For those with Partial Home backup, at what stage do you get to specify which circuits go in the backup subpanel, and which circuits will be left in the main panel? Specifying which combination of circuits can be backed up and which ones cannot would also have helped me arrive at a decision but Tesla did not specify.
AC slow-start was part of the Tesla Install - i did not even know about it to ask for it.
 

jrweiss98020

Tessa's Tesla
Jan 9, 2020
432
303
Edmonds, WA
Maybe you can find out what Tesla's criteria are for whole-house backup...

I have 2 PWs and whole-house backup. However, Tesla did not install them - a local installer did. Even if I don't charge my car, my double electric oven, electric dryer, furnace blower, and a couple space heaters could easily exceed the 10 KW available...
 

Electrph

Member
Aug 29, 2019
392
233
Central California
soft start was installed day of install for me .. it never appeared anywhere in plans or any paperwork .. i just asked electrician about it and he said oh yes we have a soft start .. it is required for your setup ..(typical lack of communication within tesla)
 

Vines

Active Member
Jul 20, 2018
1,876
2,204
Silicon Valley, CA
Yeah, if you can figure out how to get it to work, the Tesla Energy Gateway can shed a load during a power outage, so a circuit that is on the backup loads side (such as an AC condenser) can be bypassed where it won't turn on unless the homeowner intervenes.

Powerwall Automated Load Shedding?

But as far as I'm aware, this type of load shedding feature doesn't actually work yet and Tesla needs to update the firmware to hopefully unlock the functionality.

Interesting response. I have not set one of these up yet, but was told it was working. Mostly the company I work for sells 3-5 Powerwalls, with the SGIP Large scale rebate funds to reduce the cost so most HVAC goes on the backup system. I was thinking load shedding needed maybe to be enabled in the firmware, but surprised its not working yet.

To the OP the limitation that I know of is "30A per Powerwall is the largest branch circuit allowed to be backed up." So as long as there are no branch circuit breakers larger than 60A then 2 Powerwalls is fine for your whole home backup. Not sure why Tesla is pushing back, but this is a place where educating the customer is important, glad you are here.

Its fine to have too much stuff on your backup system, as long as you know know that you may run through your whole stored energy in a couple hours if you do not manually load shed, or trip the Powerwalls into overload mode with a demand spike. As far as load calculations they do come into play but most jurisdictions are not asking the Powerwalls to be proven to run the whole house, like a generator is required to do, or automatically shed loads. The calculations you do will need to show the customer perhaps his estimated run time based on average draw or something similar.

Tesla has their way and it can be difficult to change that, and I agree that this is where a smaller installer provides value, in addition to being able to get SGIP funds for 3 or more Powerwalls.
 

h2ofun

Active Member
Aug 11, 2020
2,472
423
auburn, ca
Interesting response. I have not set one of these up yet, but was told it was working. Mostly the company I work for sells 3-5 Powerwalls, with the SGIP Large scale rebate funds to reduce the cost so most HVAC goes on the backup system. I was thinking load shedding needed maybe to be enabled in the firmware, but surprised its not working yet.

To the OP the limitation that I know of is "30A per Powerwall is the largest branch circuit allowed to be backed up." So as long as there are no branch circuit breakers larger than 60A then 2 Powerwalls is fine for your whole home backup. Not sure why Tesla is pushing back, but this is a place where educating the customer is important, glad you are here.

Its fine to have too much stuff on your backup system, as long as you know know that you may run through your whole stored energy in a couple hours if you do not manually load shed, or trip the Powerwalls into overload mode with a demand spike. As far as load calculations they do come into play but most jurisdictions are not asking the Powerwalls to be proven to run the whole house, like a generator is required to do, or automatically shed loads. The calculations you do will need to show the customer perhaps his estimated run time based on average draw or something similar.

Tesla has their way and it can be difficult to change that, and I agree that this is where a smaller installer provides value, in addition to being able to get SGIP funds for 3 or more Powerwalls.
So, can folks use the SGIP program to get 3 and more PW's with PGE still? I thought all the money was gone? Are they going ER or step?
 

CrazyRabbit

Member
Apr 21, 2020
410
124
Fort Worth TX
you are required to be able to power "expected" loads for automatic backup power sources. which means any thing that can switch on automatically, like refrigerator, heating/cooling, hot water, well pump... which means if you can't handle it in need to be on a non backup panel.
 

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