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New Powerwall Advanced Options [Toggles for charging from and discharging to grid from powerwalls]

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Indeed, it worked as expected. Interestingly, the system maintained a pretty steady net export rate to the grid during Peak hours, adjusting PW output according to house loads and PV output. See below.

Yesterday I started the day with a fairly full PW due to the old behavior model, which explains the solar exports before Peak, once the PWs hit 100%. Today the graph should look different, as I doubt I'll hit 100% PW before Peak. So I should be a net grid consumer outside of Peak, and a net exporter during Peak.

Cheers, Wayne

View attachment 797692
I am trying to understand this graph:
  • What mode are you running in? ie Cost Savings?
  • Do you have both Charge From Grid and Export turned on?
  • What is the house load around 1am? Are you charging a car?
  • What does the green going to the grid represent? Is it actually discharging the PWs during peak? So both solar production and draining your PWs to reserve is going to the grid?
  • Why is the grid return rate capped at 2.7 kW?
  • Did you hit your PW reserve just prior to the end of peak (that small blip)?
Seems if you do export power to the grid from the PWs then the utility could add up what your solar is supposed to produce and notice you return more than you make. It might take some fancy analytics but its possible.
 
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In order by paragraph:

1) Yes, Cost Savings.

2) I have "Export=Everything" and "Grid Charging=No". "Export=Everything" and "Grid Charging=Yes" is prohibited by the CPUC and PG&E, although I don't know if the app enforces that. (Edit: or otherwise refuses to violate the NEM-PS export limits under that combination.)

3) Yes, an EV.

4) In this graph mode (which took me a little while to grok), if you ignore the colors, it is showing just net import/export from the grid. The colors are trying show where that grid energy came from (export) or went to (import), with some important caveats:

Before I start exporting solar, it's not showing you the PV production which is charging the PW. When I'm exporting solar only (before Peak), it's not showing you the house load which is reducing the PV export. And when I'm exporting from both PW and PV during Peak, it's not showing you the house load, which is also powered by PV + PW.

So I prefer the earlier view that has all 4 quantities on one graph, not sure if that's still available since the app update, I haven't been reading that thread.

5) Good question, I'm not sure myself. Speculative answers, I don't have enough data yet to tell: (a) 2.7 kW is related to my PV array size (although in the PW wizard that is set to 2.4 kW DC, I think). (b) It's a fixed limit (possibly per Powerwall) for grid export behavior, (c) it forecast my Peak PV production, my house load, and knew my PW charge level, and computed that 2.7 kW was the required discharge rate to end up at the Reserve level at the end of Peak.

6) I did end up at the Reserve level, not sure if that small blip just after Peak is some final correction. If so, I think it was a mistake (undesired behavior of the algorithm).

7) As per (2) I can only export PV generation. But PG&E does know your PV size, and does look at your total annual exports, and disallows NEM credits for export in excess of what its theoretical model of your PV says you could possibly export. To enforce the "no pure ESS TOU arbitrage" rule.

Cheers, Wayne
 
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Legally? You need to check the interconnection agreement you signed with PG&E when you installed the PWs. And of course if you have PV and took the ITC on the PWs, you can charge from the grid, but then you'll need to refund the ITC to the IRS. (At least for the first 5 years of operation.)

Cheers, Wayne

In order by paragraph:

1) Yes, Cost Savings.

2) I have "Export=Everything" and "Grid Charging=No". "Export=Everything" and "Grid Charging=Yes" is prohibited by the CPUC and PG&E, although I don't know if the app enforces that.

3) Yes, an EV.

4) In this graph mode (which took me a little while to grok), if you ignore the colors, it is showing just net import/export from the grid. The colors are trying show where that grid energy came from (export) or went to (import), with some important caveats:

Before I start exporting solar, it's not showing you the PV production which is charging the PW. When I'm exporting solar only (before Peak), it's not showing you the house load which is reducing the PV export. And when I'm exporting from both PW and PV during Peak, it's not showing you the house load, which is also powered by PV + PW.

So I prefer the earlier view that has all 4 quantities on one graph, not sure if that's still available since the app update, I haven't been reading that thread.

5) Good question, I'm not sure myself. Speculative answers, I don't have enough data yet to tell: (a) 2.7 kW is related to my PV array size (although in the PW wizard that is set to 2.4 kW DC, I think). (b) It's a fixed limit (possibly per Powerwall) for grid export behavior, (c) it forecast my Peak PV production, my house load, and knew my PW charge level, and computed that 2.7 kW was the required discharge rate to end up at the Reserve level at the end of Peak.

6) I did end up at the Reserve level, not sure if that small blip just after Peak is some final correction. If so, I think it was a mistake (undesired behavior of the algorithm).

7) As per (2) I can only export PV generation. But PG&E does know your PV size, and does look at your total annual exports, and disallows NEM credits for export in excess of what its theoretical model of your PV says you could possibly export. To enforce the "no pure ESS TOU arbitrage" rule.

Cheers, Wayne
good point on 7. You will get no credit if you export more than what you are approved for, it would seem no matter the source, solar or batteries. What I am approved for is so large, ......
 
In order by paragraph:

1) Yes, Cost Savings.

2) I have "Export=Everything" and "Grid Charging=No". "Export=Everything" and "Grid Charging=Yes" is prohibited by the CPUC and PG&E, although I don't know if the app enforces that.

3) Yes, an EV.

4) In this graph mode (which took me a little while to grok), if you ignore the colors, it is showing just net import/export from the grid. The colors are trying show where that grid energy came from (export) or went to (import), with some important caveats:

Before I start exporting solar, it's not showing you the PV production which is charging the PW. When I'm exporting solar only (before Peak), it's not showing you the house load which is reducing the PV export. And when I'm exporting from both PW and PV during Peak, it's not showing you the house load, which is also powered by PV + PW.

So I prefer the earlier view that has all 4 quantities on one graph, not sure if that's still available since the app update, I haven't been reading that thread.

5) Good question, I'm not sure myself. Speculative answers, I don't have enough data yet to tell: (a) 2.7 kW is related to my PV array size (although in the PW wizard that is set to 2.4 kW DC, I think). (b) It's a fixed limit (possibly per Powerwall) for grid export behavior, (c) it forecast my Peak PV production, my house load, and knew my PW charge level, and computed that 2.7 kW was the required discharge rate to end up at the Reserve level at the end of Peak.

6) I did end up at the Reserve level, not sure if that small blip just after Peak is some final correction. If so, I think it was a mistake (undesired behavior of the algorithm).

7) As per (2) I can only export PV generation. But PG&E does know your PV size, and does look at your total annual exports, and disallows NEM credits for export in excess of what its theoretical model of your PV says you could possibly export. To enforce the "no pure ESS TOU arbitrage" rule.

Cheers, Wayne
Thanks for making this more understandable. I am most interested in not paying anything and having a backup. So now we can charge the PWs from the grid when we feel it is necessary. Rather than hoping some entity triggers Stormwatch on a dark and stormy night.
 
FYI, without many expectations I chatted with Tesla's online support (presumably L1?) to inquire about the "Energy Exports" option.

First, they confirmed that the "Permission to Export" option is just for use by people pre-PTO. I didn't ask if it was only available to people with PW+, as I don't have one. But based on the technical limits, that would be my expectation.

On the "Energy Exports" option they said that it should be available to anyone whose utility allows it. I indicated that my interconnection agreement does allow production time shifting (NEM Paired Storage, as opposed to a separate Non-Export Interconnection Agreement for the PWs) and so could they enable it? To my surprise, they did! (After lots of "let me research that for a moment" exchanges.)

Now a few caveats: I still have the Grid Charging Option available, and it is clear that "Export Everything" plus "Grid Charging Yes" is not allowed by PG&E. Nonetheless nothing in the app seems to be preventing me from doing that, although I haven't tried since I did take the ITC.

Second, as mentioned the Interconnection Agreement might not allow exporting from the ESS charged by PV. Although in CA, the CPUC says that the POCOs must offer Interconnection Agreements that do allow that, IIRC.

Lastly, the benefit of Export Everything is going to depend on the relative size of your PV array and your ESS storage capacity (number of PWs). If you can easily fill up your ESS with PV during off-peak times, then there's not as much benefit to Export Everything. I happen to have an old small PV system (2.4 kW AC or so), and a comparatively large ESS (2 PWs), so I expect I'll have plenty of ESS capacity to time shift all my PV production.

I'm interested to see how the PWs behave today, if working properly at sunrise tomorrow my PWs should be down to the reserve setting. Also, it appears to me that Tesla is still figuring out when and how to enable these new options, and for whom, and I'm not sure that L1 support was supposed to (Tesla management wise) enable it for me at this point. They clearly should have a procedure or at least warning to check Interconnection Agreements, and should disallow the prohibited configuration(s).

Cheers, Wayne
I tried chatting with Tesla support today, but seems like I got someone who didn't know and kept on confusing the option with PTO. They just kept copy and pasting different things from the support page, I'll try again later and hopefully I get someone who knows more.
 
I am most interested in not paying anything and having a backup.
Right, so if you haven't taken the ITC, and haven't signed an Interconnection Agreement specifying that you won't charge the PWs from the grid, you can turn on Grid Charging, Assuming that you are in Cost Savings Mode, that should reduce your Peak grid imports (by (almost?) ensuring the PWs are fully charged at the beginning of Peak) and reduce the time your PWs spend near Reserve level vs near 100% (by charging from the grid overnight some of the time, rather than waiting for morning PV to recharge)

But if you can't turn on Grid Charging, and you haven't signed a Non-Export Interconnection Agreement for the PWs, then you can consider turning on "Export=Everything." That should time shift some of your PV exports from off-Peak to Peak, giving you a bigger NEM credit, at the expense of increasing the time you spend at Reserve level (by discharging every (?) Peak period to Reserve level and not charging again until morning PV).

Cheers, Wayne
 
Right, so if you haven't taken the ITC, and haven't signed an Interconnection Agreement specifying that you won't charge the PWs from the grid, you can turn on Grid Charging, Assuming that you are in Cost Savings Mode, that should reduce your Peak grid imports (by (almost?) ensuring the PWs are fully charged at the beginning of Peak) and reduce the time your PWs spend near Reserve level vs near 100% (by charging from the grid overnight some of the time, rather than waiting for morning PV to recharge)

But if you can't turn on Grid Charging, and you haven't signed a Non-Export Interconnection Agreement for the PWs, then you can consider turning on "Export=Everything." That should increase the time you spend at Reserve level (by discharging to Reserve level every Peak period), but time shift some of your PV exports from off-Peak to Peak, giving you a bigger NEM credit.

Cheers, Wayne
Is there anything that I could point Tesla to specifically that says this should be allowed? Only thing I really see from NEMPS FAQ is that Battery Exports are not eligible for NEM credit, which doesn't necessarily mean exporting from battery isn't allowed at all.
 
Right, so if you haven't taken the ITC, and haven't signed an Interconnection Agreement specifying that you won't charge the PWs from the grid, you can turn on Grid Charging, Assuming that you are in Cost Savings Mode, that should reduce your Peak grid imports (by (almost?) ensuring the PWs are fully charged at the beginning of Peak) and reduce the time your PWs spend near Reserve level vs near 100% (by charging from the grid overnight some of the time, rather than waiting for morning PV to recharge)

But if you can't turn on Grid Charging, and you haven't signed a Non-Export Interconnection Agreement for the PWs, then you can consider turning on "Export=Everything." That should time shift some of your PV exports from off-Peak to Peak, giving you a bigger NEM credit, at the expense of increasing the time you spend at Reserve level (by discharging every (?) Peak period to Reserve level and not charging again until morning PV).

Cheers, Wayne
To be honest, I am not sure if we signed an agreement specifying we would not charge from the grid. How do we find out?

Also, how would they know if we did charge from the grid? Our 2 powerwalls can pull a total of 10 kW from the grid. We pull more than that charging a car.
 
Only thing I really see from NEMPS FAQ is that Battery Exports are not eligible for NEM credit
That's not quite what the NEMPS FAQ that was my first google hit ( https://www.pge.com/pge_global/comm...ggregation/NEM-Paired-Storage-Billing-FAQ.pdf ) says. It says:

"With NEMPS, since a storage device is present, only the exports that are attributed to renewable portion of the system (e.g. the solar portion) receive NEM credit" and

"Battery Storage energy exports do not get NEM credits for energy which was originally charged from the grid."

So in theory an ESS could keep track of all the PV generated, and all the power net exported, and ensure that at every point the energy exported to date does not exceed the PV generated to date. (The NEMPS FAQ statements treat energy as non-fungible, while I would think in reality the above is all that the physics really allows you to ask for.)

I don't know what the behavior of the PWs would be with "Export = Everything" and "Grid Charging = Yes". I assume it would do pure ESS TOU arbitrage, but maybe the programming has the option (not visible in the app) to instead enforce the above rule. Which would be very nice, but I'm not expecting it.

Cheers, Wayne
 
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To be honest, I am not sure if we signed an agreement specifying we would not charge from the grid. How do we find out?

Also, how would they know if we did charge from the grid? Our 2 powerwalls can pull a total of 10 kW from the grid. We pull more than that charging a car.
(1) During the ordering process, you (presumably) docusigned a PG&E Interconnection Agreement. You need to locate that document and see what it says.

(2) As mentioned, they know the PV system details and use something like PVWatts to model your PV production. If your NEM export exceeds that, your credit gets capped. Not sure if that is enforced on a billing cycle basis (monthly) or a true-up basis (annual).

Cheers, Wayne
 
That's not quite what the NEMPS FAQ that was my first google hit ( https://www.pge.com/pge_global/comm...ggregation/NEM-Paired-Storage-Billing-FAQ.pdf ) says. It says:

"With NEMPS, since a storage device is present, only the exports that are attributed to renewable portion of the system (e.g. the solar portion) receive NEM credit" and

"Battery Storage energy exports do not get NEM credits for energy which was originally charged from the grid."

So in theory an ESS could keep track of all the PV generated, and all the power net exported, and ensure that at every point the energy exported to date does not exceed the PV generated to date. (The NEMPS FAQ statements treat energy as non-fungible, while I would think in reality the above is all that the physics really allows you to ask for.)

I don't know what the behavior of the PWs would be with "Export = Everything" and "Grid Charging = Yes". I assume it would do pure ESS TOU arbitrage, but maybe the programming has the option (not visible in the app) to instead enforce the above rule. Which would be very nice, but I'm not expecting it.

Cheers, Wayne
Ah yes I did misread that sentence about the battery storage exports, but I think based on the first sentence alone that is probably enough for Tesla to deny enabling it. I will have to try my luck again later, being able to export some of my PW during Summer Peak would be really nice.
 
Ah yes I did misread that sentence about the battery storage exports, but I think based on the first sentence alone that is probably enough for Tesla to deny enabling it.
I don't follow, if you "Grid Charging = No" then all of your exports are attributable to the renewable portion of the system. Some of them just cycled through your battery first.

Anyway I would suggest locating your Interconnection Agreement and seeing what it says. If it doesn't prohibit that behavior, then I would think showing it to Tesla would show Export Options should be enabled. Although L1 support may not be set up to handle that decision process, I may have just gotten lucky.

Cheers, Wayne
 
I don't follow, if you "Grid Charging = No" then all of your exports are attributable to the renewable portion of the system. Some of them just cycled through your battery first.

Anyway I would suggest locating your Interconnection Agreement and seeing what it says. If it doesn't prohibit that behavior, then I would think showing it to Tesla would show Export Options should be enabled. Although L1 support may not be set up to handle that decision process, I may have just gotten lucky.

Cheers, Wayne
This is why I would be a horrible lawyer. That is true, PW is charged only with solar so does it matter. I am sure PGE would argue otherwise, but nothing specifically states I can’t do that from my agreement as far as I can tell. I couldn’t even get to a point where the support person would take that into consideration, so I’ll try again.
 
This is why I would be a horrible lawyer. That is true, PW is charged only with solar so does it matter. I am sure PGE would argue otherwise,
I don't agree with the last part, the FAQ, particularly the second sentence I quoted, says it is fine.

I.e. in legal speak (not math) the statement "Battery Storage energy exports do not get NEM credits for energy which was originally charged from the grid" implies "Battery Storage energy exports for energy which was not originally charged from the grid do get NEM credits".

Cheers, Wayne
 
This also influences the decision to take the ITC, as I want to stay on the up and up. I believe to take the ITC you have to charge those batteries at least 75% from renewable resources. So I think I could do some grid charging and still take the ITC.
I have two Powerwalls and didn't take the ITC on them since they were SGIP. I'm considering adding a third Powerwall and take the ITC on it.

Since I don't have the control over which Powerwalls are charged from the grid it seems reasonable that as long as I didn't exceed 67% of the total storage capacity on an annual basis when charging from the grid that I am still compliant with the ITC requirements.

Comments?
 
(2) As mentioned, they know the PV system details and use something like PVWatts to model your PV production. If your NEM export exceeds that, your credit gets capped. Not sure if that is enforced on a billing cycle basis (monthly) or a true-up basis (annual).

Cheers, Wayne
I believe it is on a billing cycle basis. When PG&E double-counted my electricity one month (both directions), the cap was applied immediately and affected the NEM credits.
 
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(1) During the ordering process, you (presumably) docusigned a PG&E Interconnection Agreement. You need to locate that document and see what it says.

(2) As mentioned, they know the PV system details and use something like PVWatts to model your PV production. If your NEM export exceeds that, your credit gets capped. Not sure if that is enforced on a billing cycle basis (monthly) or a true-up basis (annual).

Cheers, Wayne
It has been enforced on a monthly basis for me
 
FYI, without many expectations I chatted with Tesla's online support (presumably L1?) to inquire about the "Energy Exports" option.

First, they confirmed that the "Permission to Export" option is just for use by people pre-PTO. I didn't ask if it was only available to people with PW+, as I don't have one. But based on the technical limits, that would be my expectation.

On the "Energy Exports" option they said that it should be available to anyone whose utility allows it. I indicated that my interconnection agreement does allow production time shifting (NEM Paired Storage, as opposed to a separate Non-Export Interconnection Agreement for the PWs) and so could they enable it? To my surprise, they did! (After lots of "let me research that for a moment" exchanges.)

Now a few caveats: I still have the Grid Charging Option available, and it is clear that "Export Everything" plus "Grid Charging Yes" is not allowed by PG&E. Nonetheless nothing in the app seems to be preventing me from doing that, although I haven't tried since I did take the ITC.

Second, as mentioned the Interconnection Agreement might not allow exporting from the ESS charged by PV. Although in CA, the CPUC says that the POCOs must offer Interconnection Agreements that do allow that, IIRC.

Lastly, the benefit of Export Everything is going to depend on the relative size of your PV array and your ESS storage capacity (number of PWs). If you can easily fill up your ESS with PV during off-peak times, then there's not as much benefit to Export Everything. I happen to have an old small PV system (2.4 kW AC or so), and a comparatively large ESS (2 PWs), so I expect I'll have plenty of ESS capacity to time shift all my PV production.

I'm interested to see how the PWs behave today, if working properly at sunrise tomorrow my PWs should be down to the reserve setting. Also, it appears to me that Tesla is still figuring out when and how to enable these new options, and for whom, and I'm not sure that L1 support was supposed to (Tesla management wise) enable it for me at this point. They clearly should have a procedure or at least warning to check Interconnection Agreements, and should disallow the prohibited configuration(s).

Cheers, Wayne

I don't see the option for "Export Everything" only "Grid Charging". Do you have a screenshot to share?