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Max Number of Permittable Powerwalls [in Napa County CA]

slazinger_7

Member
Oct 7, 2020
47
10
California
Does anyone know if there's a limit on the number of Powerwalls that can be installed in a home?

We are located in Napa County and our service is with PGE. We have a ~17kW ground-mount solar and our NEC peak demand calculation is about 47 kW, if that makes a difference.

The back story is that we have had major problems with our Powerwall installation, including that Tesla's engineering department has continuously gotten our house load calculations wrong. We have a 400 amp incoming service and Tesla decided that they needed split that service into two 200 amp sub-panels (it's debatable whether this really needs to be done in the first place because the NEC calculations come out to about 190 amp, whereby we should be able to put everything behind a single TEG - our continuous loads using the Green Button have been no higher than about 60 amp in the last 2 years as a result of home energy efficiency upgrades).

Splitting the system into two means that our power output from the Powerwall banks was cut in half, namely we have 2 Powerwalls behind two TEGs (we ordered 4 Powerwalls total). After install, we experienced brown-outs during the stress tests and our AC's were either not able to start or were prematurely shutting down (along with other equipment). That was 7 months ago.

Tesla has since admitted that each TEG needs at least 1 more Powerwall to function correctly (and more likely 2). Tesla had agreed to install one more Powerwall behind each TEG (6 total) if we paid more, but the story today is that there is a "site cap" of 5 Powerwalls for residential projects. Apparently anything over 5 is considered "commercial" and prohibited.

I'm almost certain that we have neighbors that have many more - I even seem to recall talking with the on-site Tesla installers who told me they have installed a dozen or more Powerwalls in residential homes in the area. So, this doesn't make any sense.
 

zanary

Active Member
Jan 25, 2017
1,525
1,748
SF Bay Area (East Bay), CA
There is a technical limit of 10, however each county has restrictions depending on the type of home you live in. I'm in a townhouse (end unit) complex with four joining units, and I'm only allowed up to 6 per building code. So it really depends. Your permit/buidling office can tell you how many they allow.

I currently have a 200 amp service, 10 panels and 3 power walls.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
11,491
13,390
Riverside Co. CA
Perhaps PM @Vines and ask? I get the impression that the company he works for tends to do fairly large, custom installs. I am guessing he would know this fairly quickly.
 

holeydonut

Active Member
Supporting Member
Jun 27, 2020
2,364
1,707
East Bay NorCal
Does anyone know if there's a limit on the number of Powerwalls that can be installed in a home?

We are located in Napa County and our service is with PGE. We have a ~17kW ground-mount solar and our NEC peak demand calculation is about 47 kW, if that makes a difference.

The back story is that we have had major problems with our Powerwall installation, including that Tesla's engineering department has continuously gotten our house load calculations wrong. We have a 400 amp incoming service and Tesla decided that they needed split that service into two 200 amp sub-panels (it's debatable whether this really needs to be done in the first place because the NEC calculations come out to about 190 amp, whereby we should be able to put everything behind a single TEG - our continuous loads using the Green Button have been no higher than about 60 amp in the last 2 years as a result of home energy efficiency upgrades).

Splitting the system into two means that our power output from the Powerwall banks was cut in half, namely we have 2 Powerwalls behind two TEGs (we ordered 4 Powerwalls total). After install, we experienced brown-outs during the stress tests and our AC's were either not able to start or were prematurely shutting down (along with other equipment). That was 7 months ago.

Tesla has since admitted that each TEG needs at least 1 more Powerwall to function correctly (and more likely 2). Tesla had agreed to install one more Powerwall behind each TEG (6 total) if we paid more, but the story today is that there is a "site cap" of 5 Powerwalls for residential projects. Apparently anything over 5 is considered "commercial" and prohibited.

I'm almost certain that we have neighbors that have many more - I even seem to recall talking with the on-site Tesla installers who told me they have installed a dozen or more Powerwalls in residential homes in the area. So, this doesn't make any sense.


Lol I want to see the house with a dozen Powerwalls... it'd have so many disconnects and bollards... cooooooool.

I second the notion that @Vines is your person to contact for knowledge. Unfortunately I believe the company he works for doesn't like to do add-on projects to existing systems. But he should be able to give you knowledge/questions to take back to your Tesla rep.

I think the site cap you're running into is likely more to do with moving into NEM2 Multi Tarriff (NEM2-MT) with PG&E. A residential site can still be treated as a large-generator "multi tariff" location if the installer submits to PG&E for PTO at this tier. But, NEM2 MT costs much more money to obtain PTO (like I think it's $1,500 just to get PTO), and also requires the homeowner to get insurance naming PG&E in case the large site damages PG&E's equipment. I know this because... I am lame and suffered the indignity of adding PG&E to my homeowners insurance policy*.

This is the tier of NEM2 above the normal residential NEM2-PS (paired storage). From what I gathered researching stuff, Tesla has basically torpedoed their staff that used to handle the unique and special-snowflake residential installs in California.

Tesla/SolarCity has long stopped doing large installs under the California SGIP program for government incentives on residential battery systems over 10 kW. Based on the state filings, Tesla Energy continued to rake in a lot of credit/rebate from the state on municipal and large scale projects. But Tesla stopped helping individual homeowners with complex large systems and rebates since it took a lot of time and slowed Tesla down. I don't think Tesla will even PTO a project that requires NEM2-MT now which might mean they're capping you at a number of residential Powerwalls.

* Note: you should have heard my insurance guy when I said I wanted to add PG&E as a named insured on my policy. He was like "you want to what now? They think you're going to set them on fire before they set you on fire???"
 

Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
Does anyone know if there's a limit on the number of Powerwalls that can be installed in a home?

We are located in Napa County and our service is with PGE. We have a ~17kW ground-mount solar and our NEC peak demand calculation is about 47 kW, if that makes a difference.

The back story is that we have had major problems with our Powerwall installation, including that Tesla's engineering department has continuously gotten our house load calculations wrong. We have a 400 amp incoming service and Tesla decided that they needed split that service into two 200 amp sub-panels (it's debatable whether this really needs to be done in the first place because the NEC calculations come out to about 190 amp, whereby we should be able to put everything behind a single TEG - our continuous loads using the Green Button have been no higher than about 60 amp in the last 2 years as a result of home energy efficiency upgrades).

Splitting the system into two means that our power output from the Powerwall banks was cut in half, namely we have 2 Powerwalls behind two TEGs (we ordered 4 Powerwalls total). After install, we experienced brown-outs during the stress tests and our AC's were either not able to start or were prematurely shutting down (along with other equipment). That was 7 months ago.

Tesla has since admitted that each TEG needs at least 1 more Powerwall to function correctly (and more likely 2). Tesla had agreed to install one more Powerwall behind each TEG (6 total) if we paid more, but the story today is that there is a "site cap" of 5 Powerwalls for residential projects. Apparently anything over 5 is considered "commercial" and prohibited.

I'm almost certain that we have neighbors that have many more - I even seem to recall talking with the on-site Tesla installers who told me they have installed a dozen or more Powerwalls in residential homes in the area. So, this doesn't make any sense.

I'll repost my PM response here so others can see what they have to deal with beyond 5 units.

If you are comfortable with the restriction and have such a large PW system I'd absolutely recommend going to a single TEG. However, if your loads increase, you may have to re-evaluate that choice. A good middle ground would be something like a manual or automatic transfer switch, which would energize your other 200A worth of loads , and then you can have the best of both worlds: 400A on grid, and whole-home backup off-grid. SPAN subpanels would make this a possibility to do this from your phone, at a large expense.

There is no technical reason why you cannot install 10 batteries per gateway 2, but there are some code reasons, and some SGIP and utility reasons why you may not want to.

1. If you expect SGIP then you will have to prove that you need that much demand. For instance if you ask for a rebate on 8 units, you need to show that your home has the historical demand for 40 kW of power. Looks like you could justify up to 9-10 powerwalls with your peak demand.

2. If you expect SGIP, you will need to install a Net Generation Output Meter if you install more than 9 Powerwalls. With 2 TEG, this would be a maximum of 9 powerwalls per TEG.

3. SGIP for 6 or more Powerwalls is paid out over 5 years based on you actually using them, and PGE will check. This requires a 3rd party monitoring platform for reporting to PGE, which would be included in the cost of a system if you bought from the company I work for.

4. If you install more than 5 Powerwalls in one location, then the installation will be considered commercial. A maximum of 5 may be installed in a garage, then up to 5 more could be on an exterior wall, or freestanding on a concrete pad. A maximum of 2 could be installed inside the footprint of the home, whether basement, utility or mechanical closet but not within the living space.

5. It's totally possible to build an outdoor bunker for more than 5 units in the same area, but it's quite an expense. We just had one built one in Atherton.

The company I work for generally does not expand on other peoples systems, but exceptions can be made. It sounds like Tesla's process is getting in your way since the codes changed July 1 2021. Tesla always just gives the simplest design answers possible to keep it easy and cheap for themselves.

When the firmware update comes out (whenever that is) then the new larger LRA capability would help you start those AC units assuming you have the Powerwall 2.1 units installed. If installed 7 months ago, you likely have the 2.1 units.
 

Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
Lol I want to see the house with a dozen Powerwalls... it'd have so many disconnects and bollards... cooooooool.

I second the notion that @Vines is your person to contact for knowledge. Unfortunately I believe the company he works for doesn't like to do add-on projects to existing systems. But he should be able to give you knowledge/questions to take back to your Tesla rep.

I think the site cap you're running into is likely more to do with moving into NEM2 Multi Tarriff (NEM2-MT) with PG&E. A residential site can still be treated as a large-generator "multi tariff" location if the installer submits to PG&E for PTO at this tier. But, NEM2 MT costs much more money to obtain PTO (like I think it's $1,500 just to get PTO), and also requires the homeowner to get insurance naming PG&E in case the large site damages PG&E's equipment. I know this because... I am lame and suffered the indignity of adding PG&E to my homeowners insurance policy*.

This is the tier of NEM2 above the normal residential NEM2-PS (paired storage). From what I gathered researching stuff, Tesla has basically torpedoed their staff that used to handle the unique and special-snowflake residential installs in California.

Tesla/SolarCity has long stopped doing large installs under the California SGIP program for government incentives on residential battery systems over 10 kW. Based on the state filings, Tesla Energy continued to rake in a lot of credit/rebate from the state on municipal and large scale projects. But Tesla stopped helping individual homeowners with complex large systems and rebates since it took a lot of time and slowed Tesla down. I don't think Tesla will even PTO a project that requires NEM2-MT now which might mean they're capping you at a number of residential Powerwalls.

* Note: you should have heard my insurance guy when I said I wanted to add PG&E as a named insured on my policy. He was like "you want to what now? They think you're going to set them on fire before they set you on fire???"
The last 2 homes where we installed 2 or 3 TEG systems with 12 Powerwalls both had garage installations and no impact protection required, though each TEG needed a 200A big-ole-disconnect.

Atherton is so much more reasonable about the needs of the mansions in their jurisdiction, but one of those was in Santa Clara County before they got all wound up about ESS. The 12 Powerwalls in that house have a nice view of the Ferrarri and Lamborghini in the 5 car garage.
 

Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
Does anyone know if there's a limit on the number of Powerwalls that can be installed in a home?

We are located in Napa County and our service is with PGE. We have a ~17kW ground-mount solar and our NEC peak demand calculation is about 47 kW, if that makes a difference.

The back story is that we have had major problems with our Powerwall installation, including that Tesla's engineering department has continuously gotten our house load calculations wrong. We have a 400 amp incoming service and Tesla decided that they needed split that service into two 200 amp sub-panels (it's debatable whether this really needs to be done in the first place because the NEC calculations come out to about 190 amp, whereby we should be able to put everything behind a single TEG - our continuous loads using the Green Button have been no higher than about 60 amp in the last 2 years as a result of home energy efficiency upgrades).

Splitting the system into two means that our power output from the Powerwall banks was cut in half, namely we have 2 Powerwalls behind two TEGs (we ordered 4 Powerwalls total). After install, we experienced brown-outs during the stress tests and our AC's were either not able to start or were prematurely shutting down (along with other equipment). That was 7 months ago.

Tesla has since admitted that each TEG needs at least 1 more Powerwall to function correctly (and more likely 2). Tesla had agreed to install one more Powerwall behind each TEG (6 total) if we paid more, but the story today is that there is a "site cap" of 5 Powerwalls for residential projects. Apparently anything over 5 is considered "commercial" and prohibited.

I'm almost certain that we have neighbors that have many more - I even seem to recall talking with the on-site Tesla installers who told me they have installed a dozen or more Powerwalls in residential homes in the area. So, this doesn't make any sense.
I forgot to add one more restriction, which is the impedance measurement between the transformer and the main service panel. The longer the run is, and the smaller the wiring is, the larger the impedance will be; impedance maximums limit the overall number of Powerwalls that can be installed on a single service.
 
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jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
11,491
13,390
Riverside Co. CA
If I remember what the zip code of atherton looked like, it doesnt surprise me that the city is more reasonable. The price of entry to living there in general is "high" even for bay area standards, if I remember correctly. For most of the people there, I would assume that "the money" is not on the list of concerns with these projects, and they are used to "throwing money at a problem until it goes away" (lol).
 
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BGbreeder

Member
Jun 19, 2020
497
300
Bay Area
Yes, it is regularly rank as the most expensive zip code in the country and has the highest per capita income for a city it's size. Having a minimum lot size of an acre also helps attract a certain demographic...
 

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