Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Will PGE okay charging batteries from grid with solar?

RKCRLR

Member
Apr 13, 2020
434
168
Garden Valley, CA
What I don't understand is why there would be opposition to selling energy back to the utilities as long as it is done in moderation (i.e., never have the utility owe you significant money at true-up and ignoring the ITC issue).
As long as utilities have their rate structure reflect when they really need the power back it seems like it would a win-win. They could create a specific rate structure for buying back the stored power similar to what they do for EV rates. And homeowners would have more cushion against power outages if they could recharge from the grid once they have provided power back to the utilities when they really need it.
 

Ampster

Active Member
Oct 5, 2012
1,780
477
Kenwood, California
NEM Paired Storage rules in the NEM and NEM2 tariffs specify that small systems without NGOM can only receive NEM credits for exports up to their estimated generation.
I now understand more clearly your earlier comment that implementing Virtual Power Plants will be a difficult regulatory issue.
Earlier on another thread, I was encouraged by the notion of the Connected Solutions program in Massachusetts coordinated by Tesla. A solution like that would help the grid.
 
Last edited:
  • Like
Reactions: BGbreeder

miimura

Well-Known Member
Aug 21, 2013
6,362
6,065
Los Altos, CA
I just looked at my PGE bill. See nothing like this. Now, since I have no batteries, I believe I have no paired storage, and am on TOU-c rate. Am I looking at the wrong place?
After Powerwall PTO your billing will change. The table shown is from the "black and white" bill that is only generated for Paired Storage customers. Normal Solar billing was integrated into the "Blue Bill" several years ago. My black and white bill for NEM-PS is usually about 14 letter size pages. With all the CCA billing details, most of it is nearly incomprehensible. There are a couple good tables like the one shown above. The True-Up History table below is also useful.

PG&E TrueUp History 2020-12.jpg
 
  • Like
Reactions: Ampster

miimura

Well-Known Member
Aug 21, 2013
6,362
6,065
Los Altos, CA
What I don't understand is why there would be opposition to selling energy back to the utilities as long as it is done in moderation (i.e., never have the utility owe you significant money at true-up and ignoring the ITC issue).
As long as utilities have their rate structure reflect when they really need the power back it seems like it would a win-win. They could create a specific rate structure for buying back the stored power similar to what they do for EV rates. And homeowners would have more cushion against power outages if they could recharge from the grid once they have provided power back to the utilities when they really need it.
The CPUC and PG&E really need to implement a Virtual Power Plant scheme so that we can be compensated directly for our grid support. I would think that even $1/kWh would be justifiable during Peak Demand Events.

I understand more clearly your earlier comment that implementing Virtual Power Plants will be a difficult regulatory issue.
Earlier on another thread, I was encouraged by the notion of the Connected Solutions program in Massachusetts coordinated by Tesla. A solution like that would help the grid.
Now that I think more about this, as long as you're only charging from solar, these export limitations would not really interfere with VPP demand response export. The customer would just have to have battery energy available from their solar charging to contribute to the grid. However, IMHO, merely getting Peak tariff credit is not enough. Either a seasonal capacity ($/kW) credit or a high per kWh credit (>$1/kWh) would be necessary.
 
  • Like
Reactions: arnolddeleon

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
After Powerwall PTO your billing will change. The table shown is from the "black and white" bill that is only generated for Paired Storage customers. Normal Solar billing was integrated into the "Blue Bill" several years ago. My black and white bill for NEM-PS is usually about 14 letter size pages. With all the CCA billing details, most of it is nearly incomprehensible. There are a couple good tables like the one shown above. The True-Up History table below is also useful.

View attachment 630312
so as just a solar customer now, there is no limit? Or I cannot see it.
 

miimura

Well-Known Member
Aug 21, 2013
6,362
6,065
Los Altos, CA
so as just a solar customer now, there is no limit? Or I cannot see it.
If you have no battery, there is no chance for you to "game the system" by charging from the grid during Off-Peak and getting credits during Peak. Your grid tied system will naturally export whatever your house is not using at the moment and you will get credits for everything you export.
 

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
If you have no battery, there is no chance for you to "game the system" by charging from the grid during Off-Peak and getting credits during Peak. Your grid tied system will naturally export whatever your house is not using at the moment and you will get credits for everything you export.
Yep, that is what has happened so far. I sure hope adding batteries does not eliminate this ability?

Even though I was trying to find the post from the person who posted he did lose credits since PGE implied he was gaming system. I assume he also had batteries, but cannot find his post

Want to know how they calculate since if adding batteries loses me money, maybe I would not do them?
 

miimura

Well-Known Member
Aug 21, 2013
6,362
6,065
Los Altos, CA
Yep, that is what has happened so far. I sure hope adding batteries does not eliminate this ability?

Even though I was trying to find the post from the person who posted he did lose credits since PGE implied he was gaming system. I assume he also had batteries, but cannot find his post

Want to know how they calculate since if adding batteries loses me money, maybe I would not do them?
You have nothing to worry about. The rules I quoted above are a backstop against people cheating. You will never run into these issues with Powerwalls because of how Tesla programs their operation. You can see from my tables above that the Powerwalls greatly decrease the amount of my solar export versus my estimated generation. This is because I am absorbing my solar generation to use during Peak when the solar is not outputting nearly as much.
 

arnolddeleon

Supporting Member
Jul 21, 2012
841
909
SF Bay Area
Yep, that is what has happened so far. I sure hope adding batteries does not eliminate this ability?

Even though I was trying to find the post from the person who posted he did lose credits since PGE implied he was gaming system. I assume he also had batteries, but cannot find his post

Want to know how they calculate since if adding batteries loses me money, maybe I would not do them?

I believe that's me. As @miimura noted, my case is slightly special, PG&E thinks my PV system is dramatically smaller than it actually is. They project production based on the size of the your PV system. In a battery situation where they don't have NGOM (net generation output meter) on the solar/generation PG&E doesn't know how your power was generated, it could easily have been from additional generator (e.g. non-permitted PV, a gas generator) or grid charging. This is why they have estimate your PV production as a proxy for the NGOM. The estimates seems pretty reasonable. I can't find the reference at the moment, but I believe they based in NREL data for the size of your PV system in your location. The only way you get in trouble is if you are "cheating" (e.g. selling in excess if your production) or as in my case where the records get screwed up.

PG&E used to require an NGOM for systems above a certain size. There is whole other thread on this being no longer the case.
 

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
I believe that's me. As @miimura noted, my case is slightly special, PG&E thinks my PV system is dramatically smaller than it actually is. They project production based on the size of the your PV system. In a battery situation where they don't have NGOM (net generation output meter) on the solar/generation PG&E doesn't know how your power was generated, it could easily have been from additional generator (e.g. non-permitted PV, a gas generator) or grid charging. This is why they have estimate your PV production as a proxy for the NGOM. The estimates seems pretty reasonable. I can't find the reference at the moment, but I believe they based in NREL data for the size of your PV system in your location. The only way you get in trouble is if you are "cheating" (e.g. selling in excess if your production) or as in my case where the records get screwed up.

PG&E used to require an NGOM for systems above a certain size. There is whole other thread on this being no longer the case.
Yep, I could not find your post!

So, did you put in the solar and batteries same time? If so, it was always messed up from the start. But what calculations do they use?
Size of the system they think you have times some number? I remember seeing your post where they limited you, so it is real. Just trying to make sure I do not miss something. I was able to over size my solar with permission since my electricity use was off the scale for the 12 month period in check. I maybe getting more batteries than most folks. Mainly because the way my house is wired it is like I have two homes.
 

arnolddeleon

Supporting Member
Jul 21, 2012
841
909
SF Bay Area
Yep, I could not find your post!

So, did you put in the solar and batteries same time? If so, it was always messed up from the start. But what calculations do they use?
Size of the system they think you have times some number? I remember seeing your post where they limited you, so it is real. Just trying to make sure I do not miss something. I was able to over size my solar with permission since my electricity use was off the scale for the 12 month period in check. I maybe getting more batteries than most folks. Mainly because the way my house is wired it is like I have two homes.

2002 10.9 kW solar, 2008 2.5 kW solar, 2018 2 Tesla Powerwalls. The error could have occurred as early as 2008 but it didn't matter then. I still haven't gotten anywhere with getting it fixed. I'm avoiding the issue by using "balanced", which allows me to self-consume more, instead of "cost savings" This turns out to align with my other goals anyway so currently a non-issue. I have an open solar and battery order with Tesla (it's an addiction). I'm hoping that will also fix things.

My understanding is they take the size of your PV system and use modeling data to predict how much energy it would produce. There are well known models (e.g. PVWatts Calculator) published that take PV system, efficiency data, location (lat/long) orientation and predict how the system will produce. So in my case they think I have only have 2.9 kW PV system.

In short, as long as PG&E has the correct size of your PV system I don't anticipate any problem exporting that total.
 

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
2002 10.9 kW solar, 2008 2.5 kW solar, 2018 2 Tesla Powerwalls. The error could have occurred as early as 2008 but it didn't matter then. I still haven't gotten anywhere with getting it fixed. I'm avoiding the issue by using "balanced", which allows me to self-consume more, instead of "cost savings" This turns out to align with my other goals anyway so currently a non-issue. I have an open solar and battery order with Tesla (it's an addiction). I'm hoping that will also fix things.

My understanding is they take the size of your PV system and use modeling data to predict how much energy it would produce. There are well known models (e.g. PVWatts Calculator) published that take PV system, efficiency data, location (lat/long) orientation and predict how the system will produce. So in my case they think I have only have 2.9 kW PV system.

In short, as long as PG&E has the correct size of your PV system I don't anticipate any problem exporting that total.
Just found my NEM2 form that was sent into PGE when I applied. It has my production usage with solar -20,000kwh per year so I should be fine. System solar estimate 21,466kwh per year and last 12 month usage 41,468Kwh in a year. So, I should be find. Guess I could double the size of my solar and still be okay :)
 

wwhitney

Member
Nov 2, 2017
906
1,193
Berkeley, CA
NEM Paired Storage rules in the NEM and NEM2 tariffs specify that small systems without NGOM can only receive NEM credits for exports up to their estimated generation.
Note that this wording, and the CPUC decision, do not prohibit time shifting of solar generation. So it is only Tesla that is prohibiting that by not offering the option on Powerwalls charged from solar.

Cheers, Wayne
 

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
I got this from the person who got tesla to enable grid charging



Your power company has to allow it first and foremost. SRP has it written into heir solar guidelines. Which was the only reason I got it approved.

If your using SRP they cannot deny you, I would simply call nd say that per your policy with your provider Tesla cannot legally prevent you from charging from the grid and solar. I had SRP reach out to tesla also which helped.



And then I get this from PGE website



Battery storage for your home



Potentially reduce your energy costs: If you are on a PG&E Time-of-Use rate or Home Charging rate, your battery can charge when electricity is cheaper and discharge for use in your home when electricity from the grid is more expensive.




Home battery storage systems are typically connected to both the grid and your home’s electric panel to perform two main functions:


  • Charging: you can store power generated by your home rooftop solar system — or from the grid when electricity prices are lower — to be used at a later time. If an outage is imminent due to a storm or shut off event, some storage providers are able to send a signal to your battery to fully charge before the outage, in preparation to provide backup power.
  • Discharging: you can use the energy stored by your battery to power your home when the price of electricity from the grid is more expensive, at night when your solar system isn’t producing (if you have solar), or during an outage when you need backup power.




So, how can I read this any other way than PGE supports grid charging?
 
  • Informative
Reactions: pilotSteve

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
only drawback is no 26% federal tax credit on powerwall then... but if your getting a grant, who cares then...
Yes, could care less about the ITC. So seems folks have been saying PGE does not allow. But their website page that I just linked sure seems to say they actively support this. Am I missing something?
 

holeydonut

Supporting Member
Jun 27, 2020
1,866
1,253
East Bay NorCal
I think you're mixing up the issue a bit. PG&E will allow a residential grid-tied Powerwall to charge from the grid only if:
1) Solar or other similar generation equipment is not part of the system
2) Emergency events (like a Stormwatch)

Otherwise, your Powerwalls should only be charged with the self generation equipment.


And, my understanding is at this time, PG&E will not allow a homeowner to export stored energy to the grid under any circumstance. There's an initiative to allow residential ESS to discharge to the grid if CAISO determines a possible energy shortfall, but that'll take years to roll out if ever.


PG&E may seem like they're supportive of what you want to do; but they're the ones that definitely do not homeowners being able to charge via grid or solar as a self-initiated decision. The PoCo doesn't want people to charge batteries when TOU rates are favorable to the customer, and then not use grid energy when TOU rates go up later in the day after sunset.

Also, homeowners with solar could see in the forecast that the next few days will be cloudy. So they could bank as much as possible beforehand and totally miss a day where the PoCo would rake in cash when the homeowner used a lot of grid energy due to lack of solar production.

The PoCo's simply don't want homeowners to have the freedom to do this type of arbitrage and planning. I don't think Tesla directly cares what you do. But Tesla knows they need the PoCo's on board or else their product wouldn't be approved for use with existing infrastructure.
 

h2ofun

Active Member
Aug 11, 2020
2,672
490
auburn, ca
I think you're mixing up the issue a bit. PG&E will allow a residential grid-tied Powerwall to charge from the grid only if:
1) Solar or other similar generation equipment is not part of the system
2) Emergency events (like a Stormwatch)

Otherwise, your Powerwalls should only be charged with the self generation equipment.


And, my understanding is at this time, PG&E will not allow a homeowner to export stored energy to the grid under any circumstance. There's an initiative to allow residential ESS to discharge to the grid if CAISO determines a possible energy shortfall, but that'll take years to roll out if ever.


PG&E may seem like they're supportive of what you want to do; but they're the ones that definitely do not homeowners being able to charge via grid or solar as a self-initiated decision. The PoCo doesn't want people to charge batteries when TOU rates are favorable to the customer, and then not use grid energy when TOU rates go up later in the day after sunset.

Also, homeowners with solar could see in the forecast that the next few days will be cloudy. So they could bank as much as possible beforehand and totally miss a day where the PoCo would rake in cash when the homeowner used a lot of grid energy due to lack of solar production.

The PoCo's simply don't want homeowners to have the freedom to do this type of arbitrage and planning. I don't think Tesla directly cares what you do. But Tesla knows they need the PoCo's on board or else their product wouldn't be approved for use with existing infrastructure.
who wants to export stored energy to the grid? I sure do not.

I guess I just read things differently


I worked with your sales person to put in for batteries under the SGIP ER program. Below are the requirements I could find in

the SGIP 2020 handbook V9



Section 5.2 Energy storage projects may be stand-alone or paired with generating systems and must be capable of

discharging fully at least once per day.



Residential energy storage projects,

whether stand-alone or paired, must comply with additional requirements specified in the Residential

Energy Storage Eligibility Affidavit designed to ensure that all residential energy storage systems

participating in the SGIP will be used for more than just back-up emergency purposes.


Section 5.2.5 Residential systems are required to discharge a minimum of 52 full discharges per year. A “full discharge”

is the equivalent of discharging the SGIP-incentivized energy capacity, whether it is during a single or

multiple discharges.57


57 Each discharge does not have to be a 100% depth of discharge, but the aggregate amount of discharges over the year must equate

to 104 full discharges. (residential is 52)



5.2.6 Paired with On-site Renewables

To be considered paired with and charging from on-site renewables, energy storage systems must either

be claiming the Investment Tax Credit (ITC) or, if not claiming the ITC, charge a minimum of 75% from the

on-site renewable generator.


So in summary from the SGIP handbook, it states the batteries can be charged from both the grid and solar. So nothing we need to ask SGIP

since I found all we need to know in their handbook. (Too bad they did not say all batteries have to be on one gateway ☹ )


SGIP then approved me for the batteries


Second piece of data is what does PG&E want and allow. This webpage from them makes it real clear


Battery storage for your home


Key points


Potentially reduce your energy costs: If you are on a PG&E Time-of-Use rate or Home Charging rate, your battery can charge when electricity is cheaper and discharge for use in your home when electricity from the grid is more expensive.



Home battery storage systems are typically connected to both the grid and your home’s electric panel to perform two main functions:



  • Charging: you can store power generated by your home rooftop solar system — or from the grid when electricity prices are lower — to be used at a later time. If an outage is imminent due to a storm or shut off event, some storage providers are able to send a signal to your battery to fully charge before the outage, in preparation to provide backup power.
  • Discharging: you can use the energy stored by your battery to power your home when the price of electricity from the grid is more expensive, at night when your solar system isn’t producing (if you have solar), or during an outage when you need backup power.
Please note: You do not need a home solar system to benefit from battery storage. A battery storage system can charge solely from PG&E’s grid to be used for backup power and to shift your use of grid energy to lower-price times of day. Pairing solar with your battery, however, can provide additional benefits, such as longer-lasting backup power and increased bill savings.



So from the direct PG&E site, as shown above, PG&E actively supports charging batteries from the grid when prices are low in the TOU rate, and then use the batteries when the TOU rate is high. Pretty black and white.
 
  • Like
Reactions: pilotSteve

Ampster

Active Member
Oct 5, 2012
1,780
477
Kenwood, California
PG&E may seem like they're supportive of what you want to do; but they're the ones that definitely do not homeowners being able to charge via grid or solar as a self-initiated decision.
Most of that restriction is based on Powerwall programming which is consistent with ITC rules. There may be wording in SGIP grants that i am unaware of. As a practical matter, once the power goes through your meter there is no methodology for PG&E to determine how you used it. I have a hybrid inverter and I could use the inverter or a separate battery charger to charge my batteries. I choose not to do that to preserve my Investment Tax Credit on my system.
I do agree with your statement that they are NOT supportive of these kind of initiatives but i also believe their authority does NOT extend behind the meter. I will maintain that position until the Joules come home.
 
  • Like
Reactions: BGbreeder

wwhitney

Member
Nov 2, 2017
906
1,193
Berkeley, CA
I think you're mixing up the issue a bit. PG&E will allow a residential grid-tied Powerwall to charge from the grid only if:
1) Solar or other similar generation equipment is not part of the system
2) Emergency events (like a Stormwatch)

Otherwise, your Powerwalls should only be charged with the self generation equipment.
I don't believe that's correct. Per the Interconnection Agreement I signed with PG&E for NEM with Paired Storage not more than 10kW, the only limitation on me is that (per year? per billing cycle?) for those billing intervals for which I am net exporter, the sum of those exports does not exceed their modeled PV production for your system. The only barrier to grid charging is Tesla's policy, which they have put in place to facilitate qualification for the ITC.

Cheers, Wayne
 

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