Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register
  • We just completed a significant update, but we still have some fixes and adjustments to make. Please see this thread for more details and to find out how to revert to the old design. Cheers!

Will a Tesla powerwall work for me?

Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
This maybe technically true but is it supported by Tesla? In such scenario,what stops the PV inverters from backfeeding to generator if the batteries are full?
A totally off grid system is 100% supported by Tesla. The generator is on the other side of the GW switch, so the GW has both 2 wire control to start the generator, as well as a cutoff in the GW contactor in case there is some problem.

I haven't actually done one yet totally off grid, but I think I understand the gist of it.
 

h2ofun

Active Member
Aug 11, 2020
3,106
681
auburn, ca
Different cases for different folks.

Try that same experience in a snowstorm, when you need heat to survive. Fortunately, we won't see those conditions in California unless in the high sierras.

Remember, if your powerwalls freeze, you will not be able to take a charge from PV. However if you have extra power from a generator, you could use this to activate the internal Powerwall heaters.

If you have no power in the Powerwalls at the end of the day, and little solar due to winter exposure, you will have difficulty recovering this system in a winter storm, where PV generation is low.

For the couple hours you may have PV, the powerwalls may be so cold that they cannot take that charge. If they cannot take that charge, they will turn off the PV with frequency shifting. If you have a generator you can get the batteries warm for an hour or so, then they can activate the full PV load that you may get for a couple hours. If you don't get any sun, you can at least recharge the ESS so to keep the house warm and keep the Powerwalls warm so they will accept a charge.
thanks. Makes sense for some, but for many, this stuff is interesting. I have lived in my house for 33 years. Yep, have had some power outages over the years, but never spent a dime to deal with them. The amount of money I have now spent, let alone the time and hassle factor, to deal with these so few hours in life is TOTALLY stupid, IMO!!! But since I cannot take my money with me, have been having fun with the technology.
 
A totally off grid system is 100% supported by Tesla. The generator is on the other side of the GW switch, so the GW has both 2 wire control to start the generator, as well as a cutoff in the GW contactor in case there is some problem.

I haven't actually done one yet totally off grid, but I think I understand the gist of it.
Theoretical Question:

My 3 PW setup has a Backup Gateway (or Gateway1?) and a separate panel that has:
  • one breaker for each of my powerwalls (3)
  • one breaker for each string of my PV (3)
  • one breaker for my PV monitoring system (non Tesla)

What would be the difference between setting up an additional breaker that is connected to a fourth string of PV and a breaker that is connected to a backup generator? They both energize the generation panel; it doesn't seem like the system could refuse the load that is being brought in... so what causes this type of setup to not be allowed or function? Is there something in the provisioning that identifies the source of each breaker into the panel? (CTs?)
 

cali8484

Member
Jul 8, 2018
288
171
California
A totally off grid system is 100% supported by Tesla. The generator is on the other side of the GW switch, so the GW has both 2 wire control to start the generator, as well as a cutoff in the GW contactor in case there is some problem.

I haven't actually done one yet totally off grid, but I think I understand the gist of it.

So, that suggests there is different PW setting for "true" off-grid mode where the generator is connected to the normal grid connection but with additional generator control connections and operation. It sounds similar to the Enphase generator solution where they turn on/off generator based on battery SOC thresholds and the main purpose for generator is battery charging rather than powering loads.
 

Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
Theoretical Question:

My 3 PW setup has a Backup Gateway (or Gateway1?) and a separate panel that has:
  • one breaker for each of my powerwalls (3)
  • one breaker for each string of my PV (3)
  • one breaker for my PV monitoring system (non Tesla)

What would be the difference between setting up an additional breaker that is connected to a fourth string of PV and a breaker that is connected to a backup generator? They both energize the generation panel; it doesn't seem like the system could refuse the load that is being brought in... so what causes this type of setup to not be allowed or function? Is there something in the provisioning that identifies the source of each breaker into the panel? (CTs?)
I'm picking up what you are putting down.

PV generators and Gas generators are different in several ways:
1. UL 1741 listing, the PV will turn off pretty quickly when the PW tells it to by frequency shifting
2. Output frequency, the Generator will not likely have a very clean signal, especially under a varied load.
3. Generator needs to be manually turned off.
4. Tesla rules, wild generator voltage or frequency shifting will send the system into error mode. This may damage Tesla Hardware
 

Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
So, that suggests there is different PW setting for "true" off-grid mode where the generator is connected to the normal grid connection but with additional generator control connections and operation. It sounds similar to the Enphase generator solution where they turn on/off generator based on battery SOC thresholds and the main purpose for generator is battery charging rather than powering loads.
There is a unique mode for off grid installations, the generator connects where the grid would be. The generator start control uses existing pins on the DC control bus.
 
  • Like
Reactions: MJ_CA_2019

Lloyd

Well-Known Member
Supporting Member
Jan 12, 2011
6,339
2,209
San Luis Obispo, CA
I had some push back for support from Tesla..... In fact they threatened to not allow my installation. I finally got this response:


Thank you for your patience. I have received word from my tier 2 team regarding your case. We only design off-grid systems for customers who are unable to receive electricity from a local utility company, but not for customers who already have service from a local utility company. It was mentioned that it would be fine if you decide to work with a Certified Tesla Installer to re-design to go completely off-grid which will not void your warranty as long as the limited warranty guidelines are followed. It was advised that if the off-grid requirements are not followed then performance cannot be guaranteed. I have included a link for the warranty document and how to find a Certified Tesla Installer in your area below.



Limited Warranty for Powerwall 2

https://www.tesla.com/sites/default/files/pdfs/powerwall/powerwall_2_ac_warranty_us_1-4.pdf



List of Certified Tesla Installers

Find a Tesla Certified Installer


I was hoping for a little stronger support, but I am satisfied that using off grid (disconnected from PG&E) will not void the warranty that I have with Tesla. I am using a certified installer to complete the installation. I hope that my case will encourage others to follow and "cut the cord" !

Presently I am waiting for the generator to be delivered to complete the process. It is supposed to ship next week! I ordered it in May and deliveries are backlogged.
 

h2ofun

Active Member
Aug 11, 2020
3,106
681
auburn, ca
I had some push back for support from Tesla..... In fact they threatened to not allow my installation. I finally got this response:


Thank you for your patience. I have received word from my tier 2 team regarding your case. We only design off-grid systems for customers who are unable to receive electricity from a local utility company, but not for customers who already have service from a local utility company. It was mentioned that it would be fine if you decide to work with a Certified Tesla Installer to re-design to go completely off-grid which will not void your warranty as long as the limited warranty guidelines are followed. It was advised that if the off-grid requirements are not followed then performance cannot be guaranteed. I have included a link for the warranty document and how to find a Certified Tesla Installer in your area below.



Limited Warranty for Powerwall 2

https://www.tesla.com/sites/default/files/pdfs/powerwall/powerwall_2_ac_warranty_us_1-4.pdf



List of Certified Tesla Installers

Find a Tesla Certified Installer


I was hoping for a little stronger support, but I am satisfied that using off grid (disconnected from PG&E) will not void the warranty that I have with Tesla. I am using a certified installer to complete the installation. I hope that my case will encourage others to follow and "cut the cord" !

Presently I am waiting for the generator to be delivered to complete the process. It is supposed to ship next week! I ordered it in May and deliveries are backlogged.
So, seems you now have grid connections? If so, how are you going about being able to cut if off?
 

Lloyd

Well-Known Member
Supporting Member
Jan 12, 2011
6,339
2,209
San Luis Obispo, CA
So, seems you now have grid connections? If so, how are you going about being able to cut if off?
Well.... I will ask for a disconnection. PGE told me that was all I had to do. If I don't pay the bill, what will they do? Cut me off? Anyway, I am prepared with a stack of legal precedents to be able to not have their service if they refuse.
 
  • Like
Reactions: morph3ous

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
11,557
13,476
Riverside Co. CA
Well.... I will ask for a disconnection. PGE told me that was all I had to do. If I don't pay the bill, what will they do? Cut me off? Anyway, I am prepared with a stack of legal precedents to be able to not have their service if they refuse.

I am interested to hear how this comes out, and believe you likely will have a legal battle on your hands. It sounds like you are ready to fight that battle, so let us know how it comes out.

I said this before, but I am convinced that PGE did not understand the question when you said you wanted to "disconnect service" Similar to the questions that @h2ofun had when you said "off grid" which can mean both "the grid is down on my property right now" and "I have no connection at all to the grid" depending on context, "disconnect PGE" can mean "I am moving so I want to turn off service" or "I want you to come take the meter off my property, even though I am already connected".

Its my guess you said "disconnect" and no matter how you explained it, they "heard" turn off" not "remove completely and never have the ability to turn it back on without physical re work".

So, I would encourage you to be prepared for confusion and pushback when you actually want to have them remove service completely, while still living there.
 
  • Like
Reactions: h2ofun

BGbreeder

Member
Jun 19, 2020
501
301
Bay Area
I'm picking up what you are putting down.

PV generators and Gas generators are different in several ways:
1. UL 1741 listing, the PV will turn off pretty quickly when the PW tells it to by frequency shifting
2. Output frequency, the Generator will not likely have a very clean signal, especially under a varied load.
3. Generator needs to be manually turned off.
4. Tesla rules, wild generator voltage or frequency shifting will send the system into error mode. This may damage Tesla Hardware
On number 2: the one place where I saw Tesla approved generators called out, they weren't particularly clean generators, i.e. none of them were inverter generators, but I can no longer find an approved generator list on Tesla.com, so who knows?

There is also the issue of aligning (synchronizing) the frequency between the generator and the Powerwall/solar, which is why the generator needs to be on the far side of the gateway for completely off grid installations to allow the gateway to merge the generator only when the two micro grids are in synchrony. Bad things would happen to lots of devices if that weren't the case.

I also presume, but don't know, that the gateway needs to be programmed to never push power toward the generator, i.e. "export".

All the best,

BG
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
11,557
13,476
Riverside Co. CA
On number 2: the one place where I saw Tesla approved generators called out, they weren't particularly clean generators, i.e. none of them were inverter generators, but I can no longer find an approved generator list on Tesla.com, so who knows?

There is also the issue of aligning (synchronizing) the frequency between the generator and the Powerwall/solar, which is why the generator needs to be on the far side of the gateway for completely off grid installations to allow the gateway to merge the generator only when the two micro grids are in synchrony. Bad things would happen to lots of devices if that weren't the case.

I also presume, but don't know, that the gateway needs to be programmed to never push power toward the generator, i.e. "export".

All the best,

BG

Note that I realize the conversation is pretty far off topic from what the OP asked at this point. Some of it is relevant, since the questions started as around "do powerwalls make sense in this situation", but the current conversation around generators etc is certainly off topic.

With that being said, @BGbreeder , in the thread I linked earlier, @Lloyd listed a few generator models. I am not familiar with generators at all, but since this information was already posted here figured I would find it and link for you if you were looking for it.

Tesla recommends Three Generators:

Kohler RESA 8 kw to 20 kw
Kubota GL series
Himoinsa HYW single phase series
 

jrweiss98020

Tessa's Tesla
Jan 9, 2020
503
374
Edmonds, WA
  • I have an interest in using the Powerwall primarily as a source of backup energy in case of outages
    • is this foolish and/or overkill?
  • Does anyone here charge their Powerwill solely with the grid with this purpose in mind?
    • I am getting the sense from local solar companies that I do not have an ideal property for solar. I believe I could put up enough panels to charge a Powerwall, but I would not have enough solar power to significantly offset my power bills. So, I am thinking of a small solar array with 1-2 Powerwalls as a option for backup power
      • The other option is a natural gas generator. They are loud, expensive and need a huge chunk of my lawn to function. I am still trying to compare cost of a small solar array coupled with Powerwalls against a generator (equipment, electrical work, etc)
  • Does the Powerwall have software that allows you to interact with how power is allocated (ie, in an outage, can you prioritize HVAC over TV, etc)?
  • f I can't do solar, does the Powerwall still make sense?
After browsing the discussion here, I believe you will run into 2 separate issues: Will a connection that you want be allowable per electrical codes; and will Tesla do such an installation?

My recommendation is that you find a local installer that can give you the answer to the first question, and show you the available options. It is likely that Tesla would NOT perform such an installation, because they tend to ONLY support their cookie-cutter options.

Assuming the installation you want is possible, it will then come down to whether it is affordable. Enough Powerwalls to run HVAC for an extended period will be EXPENSIVE! OTOH, 2 or 3 Powerwalls can supply necessary power (fridge, lights, electronics...) for several days. You could either back up only the circuits you consider essential, or do a whole-house backup and manually turn off what you don't need. Since you only need the Powerwalls for backup power, a small solar array to recharge them at a leisurely rate is feasible. Also, that combination will make it eligible for the federal tax credit.
 
  • Like
Reactions: h2ofun

Lloyd

Well-Known Member
Supporting Member
Jan 12, 2011
6,339
2,209
San Luis Obispo, CA
So, I would encourage you to be prepared for confusion and pushback when you actually want to have them remove service completely, while still living there.
I agree that this may be a battle. I'm retiring this year and I am willing. Any documents and/or arguments that members can assist me with this will be appreciated.

I intend and am prepared to argue that:

1. Law requires that I attach to a grid. It does not say that it has to be their grid.
2. My grid is cleaner.
3. My grid is more reliable.
4. My grid is not subject to indiscriminate fee increases and thus cheaper and a known cost over the lifetime of the equipment.
4. PG&E is a monopoly.
5. New technology allows now self reliance and alternatives to public grid not addressed or considered in original connection agreements and laws.
 
  • Like
Reactions: morph3ous

Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
Well.... I will ask for a disconnection. PGE told me that was all I had to do. If I don't pay the bill, what will they do? Cut me off? Anyway, I am prepared with a stack of legal precedents to be able to not have their service if they refuse.

Just make sure PGE don't shorten your PGE service conductors if they are underground. You don't want to pay to have new ones pulled if they aren't overhead.

I think most folks are satisfied to have the grid but not really use it. Most don't consider a ICE generator better than the California grid, but more power to you.

I know cities here like Woodside have made specific ordinances that you must be on the PGE grid if you can be connected to it. The one house I know which is totally off-grid in woodside had to justify something like a 2 week outage and no loss of service, and no allowance for a gas generator, as those also aren't allowed as a primary power source.


I will be interested to see how PGE and your building department handles this.
 

Lloyd

Well-Known Member
Supporting Member
Jan 12, 2011
6,339
2,209
San Luis Obispo, CA
After browsing the discussion here, I believe you will run into 2 separate issues: Will a connection that you want be allowable per electrical codes; and will Tesla do such an installation?

My recommendation is that you find a local installer that can give you the answer to the first question, and show you the available options. It is likely that Tesla would NOT perform such an installation, because they tend to ONLY support their cookie-cutter options.

Assuming the installation you want is possible, it will then come down to whether it is affordable. Enough Powerwalls to run HVAC for an extended period will be EXPENSIVE! OTOH, 2 or 3 Powerwalls can supply necessary power (fridge, lights, electronics...) for several days. You could either back up only the circuits you consider essential, or do a whole-house backup and manually turn off what you don't need. Since you only need the Powerwalls for backup power, a small solar array to recharge them at a leisurely rate is feasible. Also, that combination will make it eligible for the federal tax credit.

1. Electrical codes are addressed and allow for off grid installations.
2. Affordable? well 50K worth of solar (18 Kw) plus 4X powerwalls, plus 14 KW generator to power the 4000 ft house with 3X ac units.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
11,557
13,476
Riverside Co. CA
Just make sure PGE don't shorten your PGE service conductors if they are underground. You don't want to pay to have new ones pulled if they aren't overhead.

I think most folks are satisfied to have the grid but not really use it. Most don't consider a ICE generator better than the California grid, but more power to you.

I know cities here like Woodside have made specific ordinances that you must be on the PGE grid if you can be connected to it. The one house I know which is totally off-grid in woodside had to justify something like a 2 week outage and no loss of service, and no allowance for a gas generator, as those also aren't allowed as a primary power source.


I will be interested to see how PGE and your building department handles this.

This appears to me that @Lloyd might be on the "ask for forgiveness later, dont ask for permission now" plan, since "the generator is due to be delivered next week". @Lloyd certainly would not be the first person to take up a cause in retirement because, they now "have the time" lol. I am not retired, I still have a decade or so left, so cant really comprehend it myself, lol.

Presently I am waiting for the generator to be delivered to complete the process. It is supposed to ship next week! I ordered it in May and deliveries are backlogged.

I agree that this may be a battle. I'm retiring this year and I am willing.
 

Lloyd

Well-Known Member
Supporting Member
Jan 12, 2011
6,339
2,209
San Luis Obispo, CA
Just make sure PGE don't shorten your PGE service conductors if they are underground. You don't want to pay to have new ones pulled if they aren't overhead.

I think most folks are satisfied to have the grid but not really use it. Most don't consider a ICE generator better than the California grid, but more power to you.

I know cities here like Woodside have made specific ordinances that you must be on the PGE grid if you can be connected to it. The one house I know which is totally off-grid in woodside had to justify something like a 2 week outage and no loss of service, and no allowance for a gas generator, as those also aren't allowed as a primary power source.


I will be interested to see how PGE and your building department handles this.
If I designed my system correctly, I should rarely or never see the generator powering the home. PGE power is 47% from Natural Gas.
 
  • Like
Reactions: Vines

Lloyd

Well-Known Member
Supporting Member
Jan 12, 2011
6,339
2,209
San Luis Obispo, CA
Just make sure PGE don't shorten your PGE service conductors if they are underground. You don't want to pay to have new ones pulled if they aren't overhead.

I will be interested to see how PGE and your building department handles this.
It's only about 30 feet! Box is right in front of the house. I believe in our area the shutoff is remotely done through the smart meter.
 

Products we're discussing on TMC...

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top