PG&E Letter - Paired Storage Billing Update

[holeydonut]

No. From the Powerwall 2 Installation manual:

NOTE: The Tesla Powerwall system supports ESS Operating Mode of Import Only, where it will not export active power from the battery to the Area EPS. The installer and the customer can select three standard modes of operation for the Powerwall: Backup, Solar Self-Powered, and Time of Use. All three of the modes of operations operate within the constraint of the Import Only ESS Operating Mode.

I've shown that language to Sunrun and PG&E on two separate occasions. Sunrun is clueless which is fine... because they don't push back. But PG&E insists that Powerwall's "import only" setup exists only in the software of the control system. They think someone can hack the provisioning of the system to enable time-based grid exporting. And they believe the Powerwall software will become buggy and just unload all its energy in a dire-worst-case scenario.

If you think the 120 percent rule on solar is annoying, imagine how annoying it becomes if your PoCo thinks the 120 percent rule needs to take into account the Powerwalls all exporting alongside the PV exporting at max load.

Anyway, I don't think anyone on TMC has ever grid-export energy using their Powerwalls... and there are some super sharp people on this forum.

 

[holeydonut]

Yep, one bad apple spoils for everyone. I have heard of folks adding panels and not following the process to recertify this is okay with PGE. But as the one set of post state, even though its a mistake, PGE is not giving the person credit over what is recorded as max generation approval.

This all makes sense, but not what is happening to you. What is behind this is what I am interested in. Since, I want to avoid this if possible.

On this NEMMT topic, I don't think it's uniquely happening to me as a targeted attack per se. As Sunrun said to me, I'm the only homeowner they've had since starting their Powerwall installs to actually read their interconnection agreement. Most homeowners are just excited and click [Docusign] without giving a damn.

But since I dislike PG&E so much, I just naturally assume they are screwing with me somehow (especially since the NEMMT fee is $800 to $900). I want to know who is paying that hefty fee (if it exists). And, I want to know if PG&E is burying loopholes in their NEMMT language to screw me later with unlimited surprise NBC's or harass me with legalese around homeowners insurance.

I mean someone over there baked in a requirement to name PG&E on the insurance for a reason; that type of language doesn't appear for no cause.

I am happy to see so many other TMC users are already on NEMMT without much negative outcome. So I'm inclined to think it doesn't really matter outside of this $900 fee. But I still think it's weird PG&E makes us go through this NEMMT song and dance just because they don't trust us to be "normal". PG&E seems to believe we're here to job them by grid exporting at peak time to take advantage of their TOU rates.

 

[sorka]

My nameplate rating on my interconnection agreement says 7.616kw. Yet because my grid voltage is 247, my system goes up to 7.9kw frequently....even in the winter.

Does this mean I'm losing 300 watts to PGE every time my system goes above 7.616kw???? This is going to happen for at least an hour every day in the summer for me.

Or perhaps their term "maximum possible solar" production already factors in grid voltage can be more than 240 volts?

 

[Redhill_qik]

My nameplate rating on my interconnection agreement says 7.616kw. Yet because my grid voltage is 247, my system goes up to 7.9kw frequently....even in the winter.

Does this mean I'm losing 300 watts to PGE every time my system goes above 7.616kw???? This is going to happen for at least an hour every day in the summer for me.

Or perhaps their term "maximum possible solar" production already factors in grid voltage can be more than 240 volts?

I'm surprised that if you have a 7.6kW inverter that you are seeing 7.9kW coming out, possible a CT measurement issue? In any case, isn't your house going to be using at least 300W during peak generation times, so the export wouldn't be below the 7.9kw?

 

[sorka]

I'm surprised that if you have a 7.6kW inverter that you are seeing 7.9kW coming out, possible a CT measurement issue? In any case, isn't your house going to be using at least 300W during peak generation times, so the export wouldn't be below the 7.9kw?

I already explained how. 247v x 32 amps = 7904. This is measured by the SE inverter and shows on the SE portal, measured by the TEG CTs and shows on the Tesla app, and the Emporia Vue2s CTs and shows in the Emporia app. They're all within a few watts of each other.

You must not have powerwalls otherwise you'd know that in advanced mode for peak, 100% of your solar is exported to the grid while your house runs on powerwalls.

There's no option in the Tesla app / TEG to self cap the export peak and send the rest to the house or PWs.

 

[Redhill_qik]

I already explained how. 247v x 32 amps = 7904. This is measured by the SE inverter and shows on the SE portal, measured by the TEG CTs and shows on the Tesla app, and the Emporia Vue2s CTs and shows in the Emporia app. They're all within a few watts of each other.

You must not have powerwalls otherwise you'd know that in advanced mode for peak, 100% of your solar is exported to the grid while your house runs on powerwalls.

There's no option in the Tesla app / TEG to self cap the export peak and send the rest to the house or PWs.

The SE7600H-US is rated for a maximum of AC power output of 7600W, AC Output voltage of 264 Vac, and continuous output current of 32A. My expectations are Solaredge would be using the power output as the limiter as allowing to get to 264V with 32A would be 8448W. Getting to 7900W is 4% over the rated max power and while there is usually at least +/-5% within system I'm still surprised to see this as I expected it to be regulated by the internal firmware to prevent stress and overheating.

I do have two Powerwalls and I'm using the Cost Savings mode with the PW powering the house during the PG&E TOU peak time period with any solar generation being exported, since this is in the evening when production is lower not a lot is being exported. What I meant by peak was peak solar production which will be occurring at Noon +/- 2 hours. This is PG&E TOU off peak time and it wouldn't make financial or efficiency sense to be running the house load from Powerwalls at this time, so your export of the 7.9kW generation would be reduced by the house load.

 

[sorka]

The SE7600H-US is rated for a maximum of AC power output of 7600W, AC Output voltage of 264 Vac, and continuous output current of 32A. My expectations are Solaredge would be using the power output as the limiter as allowing to get to 264V with 32A would be 8448W. Getting to 7900W is 4% over the rated max power and while there is usually at least +/-5% within system I'm still surprised to see this as I expected it to be regulated by the internal firmware to prevent stress and overheating.

It's totally tied to the grid voltage. For example, if I go into backup mode, the PWs output 240 volts rather than 247 and the inverter output immediately drops to 7.6kw when doing this test while at 7.9kw. There are other threads on this.

I do have two Powerwalls and I'm using the Cost Savings mode with the PW powering the house during the PG&E TOU peak time period with any solar generation being exported, since this is in the evening when production is lower not a lot is being exported. What I meant by peak was peak solar production which will be occurring at Noon +/- 2 hours. This is PG&E TOU off peak time and it wouldn't make financial or efficiency sense to be running the house load from Powerwalls at this time, so your export of the 7.9kW generation would be reduced by the house load.

This is a good point as to why it will probably not be an issue. If we were under the old program where peak started at 7 am, then it would be.

 

[sorka]

Also, does anyone know what PG&E means by maximum possible? Are they factoring in time of day and assuming your system can't produce more than a certain amount? i.e. if you could dump power to the grid at night, will PG&E know it's NOT from solar and not credit you?

Does PG&E have minute by minute data? I know are visibility into their data is on an hourly granularity and I know we get 1:1 NEM with no NBCs within hour blocks (i.e. if we put exactly 0.5 kwh into grid from 8 to 8:30 and then take out 0.5 kwh from 8:30 to 9, it's a wash with net 0 and no NBCs for that that 0.5 kwh we took off.

But does PG&E have minute by minute visibility? I ask because if you watch the power flow, the TEG is constantly balancing the grid draw when the target is 0. i.e if you're on self consumption mode, there will be power flowing to and from the grid constantly in small amounts. Sometimes it gets off balance and the grid might get 0.4 kw for a minute but the TEG compensates by drawing the same amount of power so that it's always a net 0 for the hour.

 

[h2ofun]

Also, does anyone know what PG&E means by maximum possible? Are they factoring in time of day and assuming your system can't produce more than a certain amount? i.e. if you could dump power to the grid at night, will PG&E know it's NOT from solar and not credit you?

Does PG&E have minute by minute data? I know are visibility into their data is on an hourly granularity and I know we get 1:1 NEM with no NBCs within hour blocks (i.e. if we put exactly 0.5 kwh into grid from 8 to 8:30 and then take out 0.5 kwh from 8:30 to 9, it's a wash with net 0 and no NBCs for that that 0.5 kwh we took off.

But does PG&E have minute by minute visibility? I ask because if you watch the power flow, the TEG is constantly balancing the grid draw when the target is 0. i.e if you're on self consumption mode, there will be power flowing to and from the grid constantly in small amounts. Sometimes it gets off balance and the grid might get 0.4 kw for a minute but the TEG compensates by drawing the same amount of power so that it's always a net 0 for the hour.

 

[h2ofun]

when i applied for solar the installation company filled out the calculations as to how much max power my system would put out in a year. do you have this number?

 

[miimura]

Also, does anyone know what PG&E means by maximum possible? Are they factoring in time of day and assuming your system can't produce more than a certain amount? i.e. if you could dump power to the grid at night, will PG&E know it's NOT from solar and not credit you?

Does PG&E have minute by minute data? I know are visibility into their data is on an hourly granularity and I know we get 1:1 NEM with no NBCs within hour blocks (i.e. if we put exactly 0.5 kwh into grid from 8 to 8:30 and then take out 0.5 kwh from 8:30 to 9, it's a wash with net 0 and no NBCs for that that 0.5 kwh we took off.

But does PG&E have minute by minute visibility? I ask because if you watch the power flow, the TEG is constantly balancing the grid draw when the target is 0. i.e if you're on self consumption mode, there will be power flowing to and from the grid constantly in small amounts. Sometimes it gets off balance and the grid might get 0.4 kw for a minute but the TEG compensates by drawing the same amount of power so that it's always a net 0 for the hour.

I believe the billing system only has access to the interval data reported for your account. If your Green Button Data is hourly, then any combination of flows in and out that net out to zero during that specific interval should not incur NBCs. That is my interpretation of the NEM2 tariff paragraph below. If you are on Paired Storage Billing, then it should be pretty easy to compare the Green Button Data to the Service ID Channel data shown in the black and white bill. I have never tried to do that since I am a NEM 1 customer that doesn't pay NBCs.

 

[wwhitney]

But PG&E insists that Powerwall's "import only" setup exists only in the software of the control system.

That's absolutely true, and a person knowledgeable with simple electronics could easily spoof the CTs to get the Powerwalls to export to the grid. Which is allowed if they are charged from solar only.

So I think some significant level of skepticism on PG&E's part is justifiable, but they are taking it too far.

Cheers, Wayne

 

[h2ofun]

That's absolutely true, and a person knowledgeable with simple electronics could easily spoof the CTs to get the Powerwalls to export to the grid. Which is allowed if they are charged from solar only.

So I think some significant level of skepticism on PG&E's part is justifiable, but they are taking it too far.

Cheers, Wayne

That is what I do not understand. PGE has stated it is okay to charge storage from the grid and export it. SGIP has said the same. But, tesla will not all us to follow the rules and laws. Just makes no sense so far

 

[wwhitney]

PGE has stated it is okay to charge storage from the grid and export it.

They have? I'm not aware of that. I'm under the impression that you are allowed to charge from the grid, or discharge to the grid, but not both. You have to pick one.

That is, you have to choose one of these restrictions to obey at all times (a) discharge power <= inhouse demand or (a) charging power <= solar power generated.

Cheers, Wayne

 

[h2ofun]

They have? I'm not aware of that. I'm under the impression that you are allowed to charge from the grid, or discharge to the grid, but not both. You have to pick one.

That is, you have to choose one of these restrictions to obey at all times (a) discharge power <= inhouse demand or (a) charging power <= solar power generated.

Cheers, Wayne

I think you are right. charge solar batteries, export.

But, seems we do not get to do either, no export storage if charged from solar, and now charging from grid if we have solar?

 

[sorka]

I believe the billing system only has access to the interval data reported for your account. If your Green Button Data is hourly, then any combination of flows in and out that net out to zero during that specific interval should not incur NBCs. That is my interpretation of the NEM2 tariff paragraph below. If you are on Paired Storage Billing, then it should be pretty easy to compare the Green Button Data to the Service ID Channel data shown in the black and white bill. I have never tried to do that since I am a NEM 1 customer that doesn't pay NBCs.

My green button data is no longer tracking new days:

PG&E Green Button data no longer available...

 

[miimura]

My green button data is no longer tracking new days:

PG&E Green Button data no longer available...

You should call the PG&E Solar Customer Service center and ask why your data is unavailable. My charting ends when they did my first Paired Storage Billing after my Powerwall PTO. I just checked the Green Button downloads and the "Export Usage for a Bill Period" worked as it always has. In addition, the "Export Usage for a Range of Days" also worked and the file contained usage through yesterday 23:59 when I tried today at 23:20. In case anyone is wondering, my Green Button data is reported on 15 minute intervals.