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Will PGE okay charging batteries from grid with solar?

holeydonut

Supporting Member
Jun 27, 2020
1,820
1,190
East Bay NorCal
Huh that's pretty cool then... so PG&E does actually want people with batteries to "TOU Shift" if possible.
Battery storage for your home

But then those batteries wouldn't qualify for the clean energy federal tax credit. That is interesting then that Tesla won't allow a Powerwall sold without the ITC to do this. Maybe they're worried people will just hack the code and claim both the ITC and the TOU shifting benefit?
 

Ampster

Active Member
Oct 5, 2012
1,780
477
Kenwood, California
Maybe they're worried people will just hack the code and claim both the ITC and the TOU shifting benefit?
My guess is Tesla is giving their customers a presumption based on Tesla's policy and Tesla's marketing that often show the cost net of the ITC. . That will most likely be useful if the customer gets audited and have to prove they charged from solar. I would have to show logs for my hybrid system and fortunately that is easy to do because of the way my hybrid inverter keeps data.
 

h2ofun

Active Member
Aug 11, 2020
2,657
490
auburn, ca
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
totally agree which is why I am pushing the issue.
 

h2ofun

Active Member
Aug 11, 2020
2,657
490
auburn, ca
My guess is Tesla is giving their customers a presumption based on Tesla's policy and Tesla's marketing that often show the cost net of the ITC. . That will most likely be useful if the customer gets audited and have to prove they charged from solar. I would have to show logs for my hybrid system and fortunately that is easy to do because of the way my hybrid inverter keeps data.
With SGIP ER, there is no ITC. These maybe in the extreme minority, but they did enable this for the person in Arizona, so it can be done.
 

h2ofun

Active Member
Aug 11, 2020
2,657
490
auburn, ca
Huh that's pretty cool then... so PG&E does actually want people with batteries to "TOU Shift" if possible.
Battery storage for your home

But then those batteries wouldn't qualify for the clean energy federal tax credit. That is interesting then that Tesla won't allow a Powerwall sold without the ITC to do this. Maybe they're worried people will just hack the code and claim both the ITC and the TOU shifting benefit?
I was pretty shocked when I found that PGE page which totally supports grid and solar charging.

With SGIP ER, there is no ITC. These maybe the minority, but with this new program, my goal is to have them meet our needs, but not impact all the others. Been done in arizona, so it technically can be done.

What someone does on their taxes should be of no interest or concern to Tesla or anyone else. It is up to the IRS to deal with stuff like this.
 

holeydonut

Supporting Member
Jun 27, 2020
1,820
1,190
East Bay NorCal
Random question (asking for a friend), what's stopping someone from getting a AC/AC converter that is grid tied and hooking it up to the generation panel of a PV/ESS setup with a slightly higher voltage bump? Wouldn't the TEG view this as "generation" from solar and would just bank the energy back into the batteries as if it were clean energy coming in?

Of course there would be some conversion losses... but you know... for science.
 

wwhitney

Member
Nov 2, 2017
898
1,184
Berkeley, CA
You could totally add additional current through the solar CTs, and spoof the Gateway into thinking there is more solar production than there is. The system should respond by charging at a higher rate, and so you would be partially grid charging.

Cheers, Wayne
 
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Reactions: pilotSteve

h2ofun

Active Member
Aug 11, 2020
2,657
490
auburn, ca
You could totally add additional current through the solar CTs, and spoof the Gateway into thinking there is more solar production than there is. The system should respond by charging at a higher rate, and so you would be partially grid charging.

Cheers, Wayne
Interesting. I am aware of some folks who have make grid charging happen on the gateway. But, based on my research, it seems totally legal, and even encouraged by PG&E, to do this totally above board and legal. I am only doing this because I am using the SGIP Energy resiliency process, and fully understand the normal ITC batteries would not qualify.
 

Vines

Active Member
Jul 20, 2018
1,895
2,236
Silicon Valley, CA
One easy way that other users are doing to grid charge is to assign a set of Load CT's as PV CT's, and oriented backwards.

When this load is turned on, in addition to the load being powered, the batteries will charge from the grid at the same rate as the load is drawing.

This is not something Tesla wants you to do however.
 
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Reactions: BGbreeder

swedge

Member
May 12, 2020
81
66
Oakland, CA
Also, with regards to charging from the grid and "selling" the energy back to PG&E, I really don't understand the issue.
RK...

At least in my case, when PG&E gave me Permission To Operate my single PowerWall, they switched me to "complex billing". Each month they send a bill with the PG&E logo in blue but with no electric detail, just the $. They also send a separate b&w bill which has all of the extensive electric details, nothing but initials to maximize consumer befuddlement. However, these details include a calculation, based on a model, of how many solar kWh my system can possibly produce in that month, The number of kWh for which they credit me for putting onto the grid is limited to that amount. I gather this is what reassures PG&E that I don't charge from grid cheaply and then export to the grid at peak pricing.

Interestingly, they do not appear to check if my export occurs durning daylight hours, so it might still be possible to game the system.

In any case, PowerWall's are programmed not to export battery power to the grid.

SW
 
Last edited:

h2ofun

Active Member
Aug 11, 2020
2,657
490
auburn, ca
RK...

At least in my case, when PG&E gave me Permission To Operate my single PowerWall, they switched me to "complex billing". Each month they send a bill with the PG&E logo in blue but with no electric detail, just the $. They also send a separate b&w bill which has all of the extensive electric details, nothing but initials to maximize consumer befuddlement. However, these details include a calculation, based on a model, of how many solar kWh my system can possibly produce in that month, The number of kWh for which they credit me for putting onto the grid is limited to that amount. I gather this is what reassures PG&E that I don't charge from grid cheaply and then export to the grid at peak pricing.

Interestingly, they do not appear to check if my export occurs durning daylight hours, so it might still be possible to game the system.

In any case, PowerWall's are programmed not to export battery power to the grid.

SW
I know I have zero interest to try and game the system and send back power from the batteries. Glad to hear they cannot anyways.
 

Vines

Active Member
Jul 20, 2018
1,895
2,236
Silicon Valley, CA
One easy way that other users are doing to grid charge is to assign a set of Load CT's as PV CT's, and oriented backwards.

When this load is turned on, in addition to the load being powered, the batteries will charge from the grid at the same rate as the load is drawing.

This is not something Tesla wants you to do however.

Just to be clear I do not recommend the above.

The correct way to do what you want according to Tesla is to set those batteries up with no PV CT and no PV on the backup side.
 

getakey

Active Member
Jan 28, 2020
1,309
428
95762
However, these details include a calculation, based on a model, of how many solar kWh my system can possibly produce in that month, The number of kWh for which they credit me for putting onto the grid is limited to that amount.

This is the ~12 page B&W bill. Where is that calc? I'm interested in what they show for me
 

swedge

Member
May 12, 2020
81
66
Oakland, CA
This is the ~12 page B&W bill. Where is that calc? I'm interested in what they show for me
On my Dec bill, B&W page 3 (it may be on a different page on yours), the section is titled "Paired Storage: Maximum Export Estimation". They estimated -276 kWh for my 3.85 kW (DC) system. That works out to an average of 8.9 per day for 31 days. My actual highest DC production was 9.33 kWh on 12/23, so their estimate for AC is pretty close. (I find it interesting that happened so close to the 12/21 solstice, the shortest daylight of the year.) In any case, PW and the house used most of the production, so and PG&E shows only -18 was exported to the gird all month, so that is the "Generation Elegible For Credit" which PG&E used in several places on the rest of the (largely unintelligible) B&W bill.

SW
 
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swedge

Member
May 12, 2020
81
66
Oakland, CA
The correct way to do what you want according to Tesla is to set those batteries up with no PV CT and no PV on the backup side.

One problem with with this "solution" is that if the PV is on the grid side of the gateway, (i.e. the backup side), then PV will not be available to charge the PW or contribute to offset consumption during a grid outage. Or do I misunderstand Tesla's proposal.

It'd be OK for short outages, but it defeats the PW ability to use PV during blackouts.
 

getakey

Active Member
Jan 28, 2020
1,309
428
95762
On my Dec bill, B&W page 3 (it may be on a different page on yours), the section is titled "Paired Storage: Maximum Export Estimation". They estimated -276 kWh for my 3.85 kW (DC) system. That works out to an average of 8.9 per day for 31 days. My actual highest DC production was 9.33 kWh on 12/23, so their estimate for AC is pretty close. (I find it interesting that happened so close to the 12/21 solstice, the shortest daylight of the year.) In any case, PW and the house used most of the production, so and PG&E shows only -18 was exported to the gird all month, so that is the "Generation Elegible For Credit" which PG&E used in several places on the rest of the (largely unintelligible) B&W bill.

SW

Interesting. I have an NGOM so they know exactly what I'm generating. The section on my Bill is "Metered Export Calculation". It is on page 3. I did not notice it before
 

RKCRLR

Member
Apr 13, 2020
422
157
Garden Valley, CA
A step in the right direction would be for Tesla to allow us to charge from the grid as long we don't exceed the Maximum Export Estimation.
Charging from the grid isn't all panacea. You'll have increased NBCs, efficiency loss, and decreased powerwall life due to additional cycling. I'd let the solar recharge them if it was going to be available the next day. My main objective would be to be able to recharge them from the grid off-peak on cloudy days so I could run my home off the powerwalls during peak periods and to be better prepared for power outages.
 

aesculus

Still Trying to Figure This All Out
May 31, 2015
4,468
2,537
Northern California
And I would like to export my stored solar energy at anytime, not just when it was produced. The CAPUC says that is OK so we need to get Tesla to add it to the PW algorithm, right after they fix my MCU1. :D
 

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