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PG&E Customers with 3 or more PWs: Interconnection NEM2, NEM2-MT, or NEM2-PS

holeydonut

Supporting Member
Jun 27, 2020
1,275
769
East Bay NorCal
For what it's worth, that's actually correct, as far as the 2017 NEC, in force in California. It is only with 2020 NEC and its recognition of Power Control Systems that you wouldn't have to consider the Powerwall inverters.

But usually it's moot, as the the main disconnect is just a 200A feeder (any other breakers are removed), so the 120% ruled doesn't apply there. And the feeder topology is arranged so that there are no panels subject to the 120% rule. Are you sure it wasn't just that PG&E was misunderstanding the alternatives to the 120% rule?

Cheers, Wayne



Yeah that day I posted the 120 percent NEC rule, I had been stuck on the stupidest planning meeting. Sunrun forbids customers from talking to engineers and designers (just like in Office Space). So the one Sunrun rep on the call was franticly trying to text me so I could respond to PG&E. Sunrun wouldn't even send me the flippin' line diagram. I had to go off of what was being explained to me. Talk about the blind leading the stupid on this.

Luckily you were here to give me insight on like a real time basis. So you helped this blind man see enough to lead PG&E and Sunrun someplace.

The gist of what I understood during that terrible exchange with Sunrun was that the PG&E planner was telling the Sunrun engineer:

1) Assume the house has a 200A main service panel
2) Assume 3x Powerwalls could each export (15 kW total AC)
3) Assume 23 Enphase IQ7+ (6.7 kW AC)

They calculated the max potential export is 100A. For the 120 percent rule to be followed, the house loads had to be de-rated to 125A.
100A + 125A <= 200A x 1.20

Thus the TEG2 needed a 125A breaker and the sum of the home loads in total could not exceed 125A. This meant getting rid of an air conditioner.

I kept trying to tell Sunrun that the Powerwalls were not able to be grid exporting. I kept saying the only thing they should include in the 120 percent rule was the 35A coming from solar. But PG&E kept pushing back saying Powerwalls (when paired with solar) could in fact grid export. They kept accusing me of trying to bypass their NEM rules.

Ultimately we agreed (I can't tell if it was an agreement or just being massively frustrated) to put the following language in the actual permitted design.

NOTE: PRODUCERS STORAGE DEVICE(S) WILL
NOT CAUSE THE HOST LOAD TO EXCEED ITS
NORMAL PEAK DEMAND. NORMAL PEAK
DEMAND IS DEFINED AS THE HIGHEST
AMOUNT OF POWER REQUIRED FROM THE
DISTRIBUTION SYSTEM BY PRODUCERS
COMPLETE FACILITIES WITHOUT THE
INFLUENCE OR USE OF THE ENERGY
STORAGE DEVICE(S).

THE INSTALLED BATTERY IS NOT CHARGING
FROM THE GRID.

THE BATTERY IS EXPORTING TO THE GRID
UNDER NEM AND TOU.
 
  • Informative
Reactions: BGbreeder

holeydonut

Supporting Member
Jun 27, 2020
1,275
769
East Bay NorCal
I do not know directly, but I think it only requires an interconnection agreement that allows ESS energy to be exported and the software to match. No other hardware changes need to happen.



Oooooo guess it's worth taking a look after I get PTO.

TBH, I don't want to grid export at all. From day one, I told Sunrun that I wanted to have as little energy dependence on PG&E as I could afford. If possible, don't want to push energy to PG&E and I don't want to take energy from PG&E. I just know I can't fit enough generation sources and batteries to be able to pull off that dream :(
 

miimura

Well-Known Member
Aug 21, 2013
6,167
5,761
Los Altos, CA
The discussion above about NEM credits is clearly set forth in the NEM and NEM2 tariffs. You cannot receive credits for export greater than your actual NGOM metered solar generation or their estimation of your solar generation if you don't have NGOM, if you are a solar + storage NEM customer.

NEM-PS Export Limits.jpg


All of this is completely separate from the size of generating system that they permit you to install. This is just about NEM credits.
 
  • Informative
Reactions: BGbreeder

holeydonut

Supporting Member
Jun 27, 2020
1,275
769
East Bay NorCal
The discussion above about NEM credits is clearly set forth in the NEM and NEM2 tariffs. You cannot receive credits for export greater than your actual NGOM metered solar generation or their estimation of your solar generation if you don't have NGOM, if you are a solar + storage NEM customer.

View attachment 639363

All of this is completely separate from the size of generating system that they permit you to install. This is just about NEM credits.


What do you think the implications are for H2ofun then? Is he ok as long as he can attest his solar generates around 20,000 kWh per year? Or does he have to actually target a net deficit of about 20,000 kWh per year since that's kind of what he calculated on his NEM application.
 

miimura

Well-Known Member
Aug 21, 2013
6,167
5,761
Los Altos, CA
What do you think the implications are for H2ofun then? Is he ok as long as he can attest his solar generates around 20,000 kWh per year? Or does he have to actually target a net deficit of about 20,000 kWh per year since that's kind of what he calculated on his NEM application.
As long as the solar PTO contains the correct equipment and installation data, there should be no problem. They estimate your solar production based on those records and compare to your exported kWh. If you exported more than your solar estimate, they will not give you the excess NEM credits for your exported power. This prevents things like charging Off-Peak and exporting during Peak. If you export only your own solar or charge Off-Peak and consume it all, this calculation doesn't come into play.

Another member here had their old solar system data wiped out in PG&E's records when he added to his solar system, so he's missing out on NEM credits.
 

wwhitney

Member
Nov 2, 2017
822
1,039
Berkeley, CA
They calculated the max potential export is 100A.
That part is correct (under the 2017 NEC).

For the 120 percent rule to be followed, the house loads had to be de-rated to 125A.
100A + 125A <= 200A x 1.20
That part is also correct, if you use a configuration of service equipment that includes a panel that can only be protected by the 120% rule. But there are other options than the 120% rule, and so to avoid this issue, ESS designers use configurations that qualify under those other rules.

So the only thing PG&E was wrong about was the necessity to apply the 120% rule, versus the alternatives.

Cheers, Wayne
 

holeydonut

Supporting Member
Jun 27, 2020
1,275
769
East Bay NorCal
That part is correct (under the 2017 NEC).


That part is also correct, if you use a configuration of service equipment that includes a panel that can only be protected by the 120% rule. But there are other options than the 120% rule, and so to avoid this issue, ESS designers use configurations that qualify under those other rules.

So the only thing PG&E was wrong about was the necessity to apply the 120% rule, versus the alternatives.

Cheers, Wayne


Well I think the part PG&E was driving me nuts about was wanting to de-rate my home loads from 200A down to 125A. And Sunrun was like "you gotta do what you gotta do to make the 120 percent calc work."

I wasn't about to shed an air conditioner. And then I'd never be able to get an EV.

PG&E knew there was a TEG2. And connected to the TEG2 were the actual home loads and PV+ESS sources. Sunrun never expected the MSP to act solely as the distribution panel for all the home loads.

What confuses me is that so many people on this forum have 3x or more Powerwalls providing whole-home backup on a property with over 125A of loads. So why isn't PG&E going out of their way to say to all these other home owners "your home loads can't exceed 125A because your PV+ESS can export 100A?"
 
Last edited:

h2ofun

Active Member
Aug 11, 2020
2,137
332
auburn, ca
Yeah that day I posted the 120 percent NEC rule, I had been stuck on the stupidest planning meeting. Sunrun forbids customers from talking to engineers and designers (just like in Office Space). So the one Sunrun rep on the call was franticly trying to text me so I could respond to PG&E. Sunrun wouldn't even send me the flippin' line diagram. I had to go off of what was being explained to me. Talk about the blind leading the stupid on this.

Luckily you were here to give me insight on like a real time basis. So you helped this blind man see enough to lead PG&E and Sunrun someplace.

The gist of what I understood during that terrible exchange with Sunrun was that the PG&E planner was telling the Sunrun engineer:

1) Assume the house has a 200A main service panel
2) Assume 3x Powerwalls could each export (15 kW total AC)
3) Assume 23 Enphase IQ7+ (6.7 kW AC)

They calculated the max potential export is 100A. For the 120 percent rule to be followed, the house loads had to be de-rated to 125A.
100A + 125A <= 200A x 1.20

Thus the TEG2 needed a 125A breaker and the sum of the home loads in total could not exceed 125A. This meant getting rid of an air conditioner.

I kept trying to tell Sunrun that the Powerwalls were not able to be grid exporting. I kept saying the only thing they should include in the 120 percent rule was the 35A coming from solar. But PG&E kept pushing back saying Powerwalls (when paired with solar) could in fact grid export. They kept accusing me of trying to bypass their NEM rules.

Ultimately we agreed (I can't tell if it was an agreement or just being massively frustrated) to put the following language in the actual permitted design.

NOTE: PRODUCERS STORAGE DEVICE(S) WILL
NOT CAUSE THE HOST LOAD TO EXCEED ITS
NORMAL PEAK DEMAND. NORMAL PEAK
DEMAND IS DEFINED AS THE HIGHEST
AMOUNT OF POWER REQUIRED FROM THE
DISTRIBUTION SYSTEM BY PRODUCERS
COMPLETE FACILITIES WITHOUT THE
INFLUENCE OR USE OF THE ENERGY
STORAGE DEVICE(S).

THE INSTALLED BATTERY IS NOT CHARGING
FROM THE GRID.

THE BATTERY IS EXPORTING TO THE GRID
UNDER NEM AND TOU.

So does this mean you can export the batteries?
 

h2ofun

Active Member
Aug 11, 2020
2,137
332
auburn, ca
Well I think the part PG&E was driving me nuts about was wanting to de-rate my home loads from 200A down to 125A. And Sunrun was like "you gotta do what you gotta do to make the 120 percent calc work."

I wasn't about to shed an air conditioner. And then I'd never be able to get an EV.

PG&E knew there was a TEG2. And connected to the TEG2 were the actual home loads and PV+ESS sources. Sunrun never expected the MSP to act solely as the distribution panel for all the home loads.

What confuses me is that so many people on this forum have 3x or more Powerwalls providing whole-home backup on a property with over 125A of loads. So why isn't PG&E going out of their way to say to all these other home owners "your home loads can't exceed 125A because your PV+ESS can export 100A?"
When I installed my solar, I have to change the 200 amp breaker in the grid panel to a 125 amp breaker.
 

h2ofun

Active Member
Aug 11, 2020
2,137
332
auburn, ca
As long as the solar PTO contains the correct equipment and installation data, there should be no problem. They estimate your solar production based on those records and compare to your exported kWh. If you exported more than your solar estimate, they will not give you the excess NEM credits for your exported power. This prevents things like charging Off-Peak and exporting during Peak. If you export only your own solar or charge Off-Peak and consume it all, this calculation doesn't come into play.

Another member here had their old solar system data wiped out in PG&E's records when he added to his solar system, so he's missing out on NEM credits.
The question is is the they want to count the batteries as an export device, great, let us do it. But, what calculation do they use. I have a solar number and how they got it. What do they do for batteries? What do they do for a battery only install?
 

holeydonut

Supporting Member
Jun 27, 2020
1,275
769
East Bay NorCal
So does this mean you can export the batteries?


Technically as far as PG&E is concerned... this language plus the NEM2-MT agreement that I signed authorize me to export from my batteries to the grid. And I can export energy from any source so long as I don't exceed the limits of the size of my system. Like I don't think I could hook up some windmills or gas generator to the Powerwalls. But I'm technically allowed to export any energy generated by the solar at any time back to the grid. So yeah, instead of pushing solar energy back at 3pm; I could bank it, then wait until peak 7pm when the rates are much more favorable.

Of course the downside is that then I wouldn't have enough energy to run my house, so I'd just end up taking energy back from PG&E.

All of this is moot. Since I had my PWs installed alongside solar... Tesla's software (assuming correctly installed gear without a funnily-placed CT) won't support grid export or load shifting.

upload_2021-2-23_18-11-26.png
 

holeydonut

Supporting Member
Jun 27, 2020
1,275
769
East Bay NorCal
When I installed my solar, I have to change the 200 amp breaker in the grid panel to a 125 amp breaker.


Lol what... so your house was NEC-calc'd to need 200A before solar, but after solar all your loads could fit under a 125A? Or did you get rid of some gear?

PS, how the heck did you use 40,000 kWh in a year with 125A service?
 
Last edited:

MJ_CA_2019

Member
Aug 19, 2020
111
26
Central CA
What confuses me is that so many people on this forum have 3x or more Powerwalls providing whole-home backup on a property with over 125A of loads. So why isn't PG&E going out of their way to say to all these other home owners "your home loads can't exceed 125A because your PV+ESS can export 100A?"

This is my setup. (photo taken before the conduit installed between the PowerWalls and the Load Center.)

The large panel on the left is the Load Center.
It has:
3 20A double pole breakers for my 3 strings of PV (microinverters)
1 15A double pole breaker for the Sunpower PV monitoring box (which is mounted above)
3 30A double pole breakers for the 3 PowerWall 2
Lighter Grey box is the Tesla backup gateway.

Large panel on the right has all my home loads.
The gray box above it contains all the extra length of the spliced lines that were brought from my Main Service Panel which is opposite all of this.
Box marked "Lumin" is the Lumin SmartControl Center. This allows for 12 breaker spaces to be configured for load shedding in a variety of ways 1) Grid outage 2) Time Based 3) Manual control. I have this because my contract with my installer included installing soft starts on my A/C units but they couldn't find an HVAC contractor to warranty it. They instead ate the cost of installing the Lumin so my larger A/C cannot run while the grid is out. (Smaller one for upstairs was fine on LRA)

My main service panel has no breakers inside it (other than the 200A service disconnect).
The MSP feeds through the wall but I don't know the term for the item.
It plugs into the bus bar and takes up two spaces to get the A and B leg. Has similar same sized wire as the service lines coming into the MSP.
Hope that makes sense.



IMG_4122.JPG
 
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h2ofun

Active Member
Aug 11, 2020
2,137
332
auburn, ca
Lol what... so your house was NEC-calc'd to need 200A before solar, but after solar all your loads could fit under a 125A? Or did you get rid of some gear?

PS, how the heck did you use 40,000 kWh in a year with 125A service?
I have 400 amp service, split to two sub panels.
 

holeydonut

Supporting Member
Jun 27, 2020
1,275
769
East Bay NorCal
Large panel on the right has all my home loads.
The gray box above it contains all the extra length of the spliced lines that were brought from my Main Service Panel which is opposite all of this.
Box marked "Lumin" is the Lumin SmartControl Center. This allows for 12 breaker spaces to be configured for load shedding in a variety of ways 1) Grid outage 2) Time Based 3) Manual control.
View attachment 639488


Yeah; so imagine if PG&E told you that the entire max allowed loads in that Square D Home loads panel + Lumin panel got de-scaled to 125A. PG&E was going to require a 125A be placed over the top of all my home loads. Because when the utility were operating, they really felt that the home could draw full load from the utility while the batteries+PV were exporting at full as well. I get the feeling your setup solves for that contingency in a smarter way than what I experienced back in November 2020.

I think (my thinking is very wrong very often) is that typically a seasoned designer would push back against PG&E to come up with a solution that doesn't just outright de-rate the home. There are solutions to the 120 percent rule when it comes to ESS + Solar, and I feel most of the people on TMC had personnel on their implementation team that solved problems for them instead of dumping problems on the homeowner.

PS, your solution is pretty cool IMO... how does Lumin learn whether or not your utility grid is operational? Is there a sensor running from the Lumin to your MSP?
 

MJ_CA_2019

Member
Aug 19, 2020
111
26
Central CA
PS, your solution is pretty cool IMO... how does Lumin learn whether or not your utility grid is operational? Is there a sensor running from the Lumin to your MSP?

I agree i was fortunate to have a design team that worked hard for what I wanted. I was adamant about having whole home backup.
When I replace my A/C units they will for sure meet the whole house requirement.
The Lumin has grid voltage detection wires that go to the MSP to determine if the grid is out or not.
 

fresnoboy

Member
Sep 13, 2017
108
33
94064
I agree i was fortunate to have a design team that worked hard for what I wanted. I was adamant about having whole home backup.
When I replace my A/C units they will for sure meet the whole house requirement.
The Lumin has grid voltage detection wires that go to the MSP to determine if the grid is out or not.

I wanted to go do a whole-house powerwall installation at our new home, and had a 400A feed as well. Because of the issues with having to do split feeds it ended up being too complicated. I would up going with a generator backup instead. We did wire in a bunch of cabling for a future installation though. I wish they would make a gateway that supported a 400A feed and integrated generator support. Maybe for Powerwall III... :)
 

h2ofun

Active Member
Aug 11, 2020
2,137
332
auburn, ca
Lol what... so your house was NEC-calc'd to need 200A before solar, but after solar all your loads could fit under a 125A? Or did you get rid of some gear?

PS, how the heck did you use 40,000 kWh in a year with 125A service?
At the time I used all that power, my house had 2 200 amp breakers. Trust me, I had to adjust stuff to not pop breakers. I was having 2K electricity bills in the dead of winter running 10 space heaters.
 

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