SDGE - Adding Battery After NEM2 Deadline, TOU, other various, etc.

[albert436]

I have seen this topic mentioned in passing a few times here, but thought I would start a thread on it.

The question is, if you add a battery later on, after the NEM2 April 14 deadline has passed, will you get kicked out of your NEM2 status?

I may give SDGE a call tomorrow if I get a chance, but it is Sunday now and I wanted to get this down while I think of it.

I was looking at the TOU charts for SDGE. Since TOU1 has more off-peak hours, I wonder why do some people (presumably) pick TOU2 ?

There is an interesting thread here about hybrid systems and getting the battery to charge and discharge at optimal times. Is that a frequent problem? How smart are these batteries? Does it depend on the inverter you choose, and are some brands better than others?

On another note, I seem to have lost the ability to PM with other people on this site. Has that function gone away, or has my ability to do that been removed?

[J.P.M.]

I have seen this topic mentioned in passing a few times here, but thought I would start a thread on it.

The question is, if you add a battery later on, after the NEM2 April 14 deadline has passed, will you get kicked out of your NEM2 status?

I may give SDGE a call tomorrow if I get a chance, but it is Sunday now and I wanted to get this down while I think of it.

I was looking at the TOU charts for SDGE. Since TOU1 has more off-peak hours, I wonder why do some people (presumably) pick TOU2 ?

There is an interesting thread here about hybrid systems and getting the battery to charge and discharge at optimal times. Is that a frequent problem? How smart are these batteries? Does it depend on the inverter you choose, and are some brands better than others?

On another note, I seem to have lost the ability to PM with other people on this site. Has that function gone away, or has my ability to do that been removed?

1.) I haven't sought or seen an answer to your battery question yet. You'd be doing all us CA users a favor by getting an answer to the adding batteries vs. getting kicked of NEM 2.0 question from the horse's mouth.

2.) PM's were disabled some years ago.

3.) If you're speaking of schedules TOU-DR1 and TOU-DR2, some users - those with PV systems - may find it more cost effective to use TOU-DR2 because they will get a better rate on generation from 2-4 P.M., particularly if they have little to no use for the super off-peak rate of TOU-DR1.
Note that both schedules are sort of hybrid TOU/Tiered rate schedules. That may be helpful, particularly for some low usage customers.

There's 2 side to rates, what you get billed for and what you get paid for.
You gotta' run the numbers for all the schedules you're considering.
I thought that most PV system owners used schedule DR-SES, although I believe users can choose any rate schedule.
Given the way the system is run there are no hard answers, just educated dart throws.
Spreadsheets with 8,760 rows help improve the aim.

[albert436]

1.) I haven't sought or seen an answer to your battery question yet. You'd be doing all us CA users a favor by getting an answer to the adding batteries vs. getting kicked of NEM 2.0 question from the horse's mouth.

2.) PM's were disabled some years ago.

3.) If you're speaking of schedules TOU-DR1 and TOU-DR2, some users - those with PV systems - may find it more cost effective to use TOU-DR2 because they will get a better rate on generation from 2-4 P.M., particularly if they have little to no use for the super off-peak rate of TOU-DR1.
Note that both schedules are sort of hybrid TOU/Tiered rate schedules. That may be helpful, particularly for some low usage customers.

There's 2 side to rates, what you get billed for and what you get paid for.
You gotta' run the numbers for all the schedules you're considering.
I thought that most PV system owners used schedule DR-SES, although I believe users can choose any rate schedule.
Given the way the system is run there are no hard answers, just educated dart throws.
Spreadsheets with 8,760 rows help improve the aim.

Thanks JP, the solar guy I'm dealing has responded to me about the batteries, and said it doesn't change anything, but I'm with you in terms of getting it from the horse's mouth.

Yes I was wondering about that and it did occur to me that the peak etc rates might also apply to what you get paid back for generating electricity.

About the batteries, the guy who did my brother's place up in northern California, he was all for the but he said they were ~$20,000. I said I thought they were more in the range of $8-12k but he scoffed even at the Teslas for $16-18K. However, looking online, though I don't see any "retail" vendors, I do see LG batteries reputed to start around $8K. There in another Chinese brand that starts around $4-6K. So that subject has got me a little stumped and I hope to get some more info on that.

I posted some replies to the guys who were having some challenges with getting their batteries to charge and discharge at appropriate times, to ask how their situations resolved. And yes they were talking TOU and spreadsheets and special programs and I don't know what all. As I said, interesting but a bit over my head at this point.

I shall report back on my findings. . .



P.S. So how much do the various batteries cost ? ? ? How much Kwh capacity do I need to keep my TV, computer, and mini split running for on peak hours?

[J.P.M.]

P.S. So how much do the various batteries cost ? ? ? How much Kwh capacity do I need to keep my TV, computer, and mini split running for on peak hours?

The answer to your question starts with the SDG & E green button data, a kill-a-watt meter and an estimate of your future use patterns.

[albert436]

Screenshot_20230212-234400.png

The answer to your question starts with the SDG & E green button data, a kill-a-watt meter and an estimate of your future use patterns.

Good point, I should get a killawatt meter !!!

BTW, from solarrights.org, lets see if I can attach a screenshot.

Edit: Link https://solarrights.org/faqnem3/

[OCJ]

Batteries are awesome, but expensive. So it's going to depend on your goal if it's worth it or not.

If you get a Powerwall, the least expensive way is with a Tesla solar system, otherwise it's 30%+ more expensive. Plus, there is other hardware involved. Like with a Powerwall, I believe you also have to add a Gateway, then you'll need some rewiring for backup loads, and non-backup loads if you're not doing whole house backup.

They do allow you to run in Self-Powered mode, as well as Time-Based Control. Self-Powered is exactly what it sounds like, it uses the least amount from the grid possible. In the summer and fall, if everything is sized right, you can get away with less than 1 kWh from the grid, and the excess going as credits.

Time-Based Control offsets On-Peak. Every cycle degrades your battery, so Time-Based Control attempts to optimize by offsetting only when it's "worth it."

In terms of what you save, think about it this way, let's say it 7pm-9pm and you save 13 kWh with your battery, that's $0.83 x 13 = $10.79 saved. Then you have to recharge it next day, so the cost is 14 kWh (not 100% efficient) at $0.52 if it's a weekday, $0.36 if it's a weekend. That's either $7.28 or $5.08 "cost", with you pocketing the $3.51 or $5.71 as a credit.

If you're a net overproducer, you'll never make your money back, but if you're a net consumer, depending on how much, you may eventually make your money back. Now installed with a Tesla system, after tax credit, it's about $7,500 so you can do the math on that one.

[albert436]

Batteries are awesome, but expensive. So it's going to depend on your goal if it's worth it or not.

If you get a Powerwall, the least expensive way is with a Tesla solar system, otherwise it's 30%+ more expensive. Plus, there is other hardware involved. Like with a Powerwall, I believe you also have to add a Gateway, then you'll need some rewiring for backup loads, and non-backup loads if you're not doing whole house backup.

They do allow you to run in Self-Powered mode, as well as Time-Based Control. Self-Powered is exactly what it sounds like, it uses the least amount from the grid possible. In the summer and fall, if everything is sized right, you can get away with less than 1 kWh from the grid, and the excess going as credits.

Time-Based Control offsets On-Peak. Every cycle degrades your battery, so Time-Based Control attempts to optimize by offsetting only when it's "worth it."

In terms of what you save, think about it this way, let's say it 7pm-9pm and you save 13 kWh with your battery, that's $0.83 x 13 = $10.79 saved. Then you have to recharge it next day, so the cost is 14 kWh (not 100% efficient) at $0.52 if it's a weekday, $0.36 if it's a weekend. That's either $7.28 or $5.08 "cost", with you pocketing the $3.51 or $5.71 as a credit.

If you're a net overproducer, you'll never make your money back, but if you're a net consumer, depending on how much, you may eventually make your money back. Now installed with a Tesla system, after tax credit, it's about $7,500 so you can do the math on that one.

That is some food for thought. But can't your Tesla Powerwall charge up from your solar panels? Or must it be charged from the grid? Or are you inferring "opportunity cost" ie. that you are not using your battery while it is charging back up the next day ?

The Self-Powered and Time-Based controls sound quite useful. My thinking was to use the battery to tide me through the 4pm to 9pm peak hours. Someone here posted a while back about their battery discharging to the grid, I don't see any advantage to that. But I think they were trying to adjust their settings to prevent that. Now if that is already built in to easy controls on the PW then that's all to the good.

So, if I understand, a Powerwall is basically a battery from Tesla. And you are saying that the Tesla PW will be already set up to work with a Tesla system, thereby avoiding some other costs associated with using a PW with another solar company's panels ?

I don't really understand about backup, non-backup, whole house backup. Also not sure what counts as a cycle, is it any discharge and recharge, or is it just when it discharges down to a certain amount? But good to have something that minimizes the impact of that.

Well it is something to think about. My neighbor mentioned something about a friend doing solar and finding that the Tesla panels were less costly, which surprised me. I have always had the impression that Tesla stuff was premium priced (???)

Well thanks, interesting points you make.

[OCJ]

That is some food for thought. But can't your Tesla Powerwall charge up from your solar panels? Or must it be charged from the grid? Or are you inferring "opportunity cost" ie. that you are not using your battery while it is charging back up the next day ?

The Self-Powered and Time-Based controls sound quite useful. My thinking was to use the battery to tide me through the 4pm to 9pm peak hours. Someone here posted a while back about their battery discharging to the grid, I don't see any advantage to that. But I think they were trying to adjust their settings to prevent that. Now if that is already built in to easy controls on the PW then that's all to the good.

So, if I understand, a Powerwall is basically a battery from Tesla. And you are saying that the Tesla PW will be already set up to work with a Tesla system, thereby avoiding some other costs associated with using a PW with another solar company's panels ?

I don't really understand about backup, non-backup, whole house backup. Also not sure what counts as a cycle, is it any discharge and recharge, or is it just when it discharges down to a certain amount? But good to have something that minimizes the impact of that.

Well it is something to think about. My neighbor mentioned something about a friend doing solar and finding that the Tesla panels were less costly, which surprised me. I have always had the impression that Tesla stuff was premium priced (???)

Well thanks, interesting points you make.

I do charge my Powerwall from solar only. Since I took the ITC in its old version I can only charge from solar for 5 years. That may have changed but I haven't looked into it. Not only that, but that option is not enabled for me anyway. The only time I ever charge from grid is during Stormwatch. So yes it's sort of the "opportunity cost", because if that excess solar wasn't going into your battery, it would be going to the grid for 1:1 credits. Really it's just load shifting.

And yes there is another option to dump all to grid at On-Peak, but I don't have that option enabled either.

You can take a look through here to see how the Powerwall works with the Gateway: https://www.tesla.com/sites/default/...ion_Manual.pdf.

For my install, my old MSP now has a single 125A branch breaker. Power goes and comes from that breaker to the Gateway 2. In the event of a grid outage, the Gateway shuts off your export to the grid because now my mains goes through it. From there it goes to my new backup panel. All my house loads were relocated there, including my 50A EV plug, 2 electric stoves, and AC. Also hooked into it is the Powerwall+, which is the Powerwall 2 + inverter. So the panels go directly to the Powerwall+, then from there to a 50A breaker in the backup panel.

Since there are CTs on the supply terminals and CTs in the inverter and Powerwall, the Gateway can direct the Powerwall to charge or discharge on coordination with my solar and house loads. Also, in the event of going off grid, it will coordinate throttling the panels to adjust to my house load so my panels will operate in a power outage.

My panels were $2.50 / watt and the Powerwall+ bundled was $10.5k.

Some people have bad experiences with Tesla solar, some have good experiences. I found the Irvine team to be professional and capable.

[albert436]

I do charge my Powerwall from solar only. Since I took the ITC in its old version I can only charge from solar for 5 years. That may have changed but I haven't looked into it. Not only that, but that option is not enabled for me anyway. The only time I ever charge from grid is during Stormwatch. So yes it's sort of the "opportunity cost", because if that excess solar wasn't going into your battery, it would be going to the grid for 1:1 credits. Really it's just load shifting.

And yes there is another option to dump all to grid at On-Peak, but I don't have that option enabled either.

You can take a look through here to see how the Powerwall works with the Gateway: https://www.tesla.com/sites/default/...ion_Manual.pdf.

For my install, my old MSP now has a single 125A branch breaker. Power goes and comes from that breaker to the Gateway 2. In the event of a grid outage, the Gateway shuts off your export to the grid because now my mains goes through it. From there it goes to my new backup panel. All my house loads were relocated there, including my 50A EV plug, 2 electric stoves, and AC. Also hooked into it is the Powerwall+, which is the Powerwall 2 + inverter. So the panels go directly to the Powerwall+, then from there to a 50A breaker in the backup panel.

Since there are CTs on the supply terminals and CTs in the inverter and Powerwall, the Gateway can direct the Powerwall to charge or discharge on coordination with my solar and house loads. Also, in the event of going off grid, it will coordinate throttling the panels to adjust to my house load so my panels will operate in a power outage.

My panels were $2.50 / watt and the Powerwall+ bundled was $10.5k.

Some people have bad experiences with Tesla solar, some have good experiences. I found the Irvine team to be professional and capable.

Amazing though I wonder what your quote would be if you got it in today's market.

Can you clarify something for me? Does Tesla have its own installation company? Or does it only license to certain installers? I am not quite clear on that. Or do you just go to their website? Someone mentioned walking into a Tesla dealer/shop, does that mean where they sell Tesla cars?

Probably these sound like dumb questions, but, you know.

[J.P.M.]

In terms of what you save, think about it this way, let's say it 7pm-9pm and you save 13 kWh with your battery, that's $0.83 x 13 = $10.79 saved. Then you have to recharge it next day, so the cost is 14 kWh (not 100% efficient) at $0.52 if it's a weekday, $0.36 if it's a weekend. That's either $7.28 or $5.08 "cost", with you pocketing the $3.51 or $5.71 as a credit.

Which SDG & E rate schedule are you using ?

Whatever schedule it is, those are summer rates in force 06/01 - 10/31, 153 days. The rest of the year the on peak to off peak differential is much less. For DR-SES for example the winter on peak to off peak rate differential is currently $0.49617/kWh - $0.43243/kWh = $0.06374/kWh.

My understanding is the Tesla Powerwall 2 has a useable capacity of 13.5 kWh and a round trip efficiency of 90%. That leaves a cycle output capacity of (13.5*.90) = 12.2 useable kWh per powerwall unit.

Now, for some back of the envelope musing, let's say you start out in the A.M at sunrise on a summer morning and go through your day and meet all your daily power needs with your array and then some plus cram an additional 13.5 kWh into your Tesla powerwall 2, all before peak rate time on a weekday.
Start out by knowing that stored energy will be less than the amount you'll need to put into it by *(1-half of a round trip efficiency penalty) = 1-.05 = 0.95kWh per kWh output from a PV system to the battery with efficiency losses. That means it will be worth less in the battery than when it went in due to efficiency losses.
So, at the instant peak time begins (at 1600 hrs. P.D.T.) you have full 13.5 kWh in a battery (that you had to input 14.21 kWh of PV to obtain) and that power cost you (13.5 kWh/0.95) * *0.52/kWh = $7.39 or $7.39/13.5 = $0.5474/kWh cost for what's currently stored in the battery.

Once peak time starts, you start drawing power from the battery. You will be offsetting power you would otherwise buy at (again, your rate numbers) $0.83/kWh. However, that rate needs to be adjusted because it too needs to also account for the other half of the round trip efficiency loss - the other half of the 10% loss.
So, the power now has a (bill offset) when delivered to a load of $0.83/kWh*.95 = $0.7885/kWh.

That leaves a savings of $0.7885 - $0.5474 = $0.24136/stored kWh for the SDG & E summer rate season.

Still using your numbers, a Tesla battery that can yield 13. 5 kWh *.9 = 12.15 kWh to do work and sells installed, after 30% tax credit for, say, $7,500 will have a price per available stored kWh of $7,500/12.15 kWh = $617.28/stored kWh.
That means that at summer rates, and if the PV system manages to generate enough every day to have 12.15 kWh into storage, using the moron method of initial cost/annual savings to gauge /guess payback on a project, a breakeven of ($617.28/kWh stored capacity) /[(153 days/yr.)*($.24136/kWh differential)] = 16.71 years, that # to be reduced by any and all winter savings to be achieved at what are quite a bit lower rate differentials, some of them quite small as noted above.

Every climate and system is different but I'd SWAG that the winter rate differentials, while helping, won't reduce that moron payback by more than 3 or 4 years. As for how sunny it gets around here, that 1530days of summer full utilization might be optimistic. I'm in zip 92026 and in 10 1/2 years here my system has generated 84,161 k

[albert436]

Which SDG & E rate schedule are you using ?

Whatever schedule it is, those are summer rates in force 06/01 - 10/31, 153 days. The rest of the year the on peak to off peak differential is much less. For DR-SES for example the winter on peak to off peak rate differential is currently $0.49617/kWh - $0.43243/kWh = $0.06374/kWh.

My understanding is the Tesla Powerwall 2 has a useable capacity of 13.5 kWh and a round trip efficiency of 90%. That leaves a cycle output capacity of (13.5*.90) = 12.2 useable kWh per powerwall unit.

Now, for some back of the envelope musing, let's say you start out in the A.M at sunrise on a summer morning and go through your day and meet all your daily power needs with your array and then some plus cram an additional 13.5 kWh into your Tesla powerwall 2, all before peak rate time on a weekday.
Start out by knowing that stored energy will be less than the amount you'll need to put into it by *(1-half of a round trip efficiency penalty) = 1-.05 = 0.95kWh per kWh output from a PV system to the battery with efficiency losses. That means it will be worth less in the battery than when it went in due to efficiency losses.
So, at the instant peak time begins (at 1600 hrs. P.D.T.) you have full 13.5 kWh in a battery (that you had to input 14.21 kWh of PV to obtain) and that power cost you (13.5 kWh/0.95) * *0.52/kWh = $7.39 or $7.39/13.5 = $0.5474/kWh cost for what's currently stored in the battery.

Once peak time starts, you start drawing power from the battery. You will be offsetting power you would otherwise buy at (again, your rate numbers) $0.83/kWh. However, that rate needs to be adjusted because it too needs to also account for the other half of the round trip efficiency loss - the other half of the 10% loss.
So, the power now has a (bill offset) when delivered to a load of $0.83/kWh*.95 = $0.7885/kWh.

That leaves a savings of $0.7885 - $0.5474 = $0.24136/stored kWh for the SDG & E summer rate season.

Still using your numbers, a Tesla battery that can yield 13. 5 kWh *.9 = 12.15 kWh to do work and sells installed, after 30% tax credit for, say, $7,500 will have a price per available stored kWh of $7,500/12.15 kWh = $617.28/stored kWh.
That means that at summer rates, and if the PV system manages to generate enough every day to have 12.15 kWh into storage, using the moron method of initial cost/annual savings to gauge /guess payback on a project, a breakeven of ($617.28/kWh stored capacity) /[(153 days/yr.)*($.24136/kWh differential)] = 16.71 years, that # to be reduced by any and all winter savings to be achieved at what are quite a bit lower rate differentials, some of them quite small as noted above.

Every climate and system is different but I'd SWAG that the winter rate differentials, while helping, won't reduce that moron payback by more than 3 or 4 years. As for how sunny it gets around here, that 1530days of summer full utilization might be optimistic. I'm in zip 92026 and in 10 1/2 years here my system has generated 84,161 k

Hey JP, I am just a teense confused.

Are we to assume that his battery discharges to the recommended level, say 20% every night from 4p-9p peak hours, and that matches his peak hours usage?

I don't get how you figured out the cost of the electricity he put into the battery. He is charging the battery only with excess PV production? So how is the 54cents figured in to it? It is not "opportunity cost", right?

As I say, I think I followed most but not all of your back of envelope figures.

[Ampster]

My take on the question of whether a battery installation after April 14th would knock you into NEM 3.0, is that the odds are good that it will not. This is based on anecdotal information from various sources including other forums and critical analysis of NEM 3.0. Also there is nothing about a battery installation that requires an IOU approval. It does require a building permit but since the battery typically does not sell or export to the grid it is not subject to a Net Energy Metering agreement. Two exceptions to that would be if you wanted SGIP funds or if you wanted to join a Virtual Power Plant.

My own risk assessment is that with a battery properly sized and programmed the downside cost of being forced into NEM 3.0 would be minimal, since the pricing of NEM 3.0 economically favors batteries. Even though it may seem wise to ask one of the IOUs about that question, I am not sure I would put much faith in the answer I received even it it was in writing. It is a risk I have taken by installing a battery without seeking permission from PG&E. To me the upside benefits far outweigh the downside risks.

I should add that my DIY cost was significantly less than the commercially available options in the marketplace. That could change the risk model for others. It may depend on where you are standing.

[albert436]

My take on the question of whether a battery installation after April 14th would knock you into NEM 3.0, is that the odds are good that it will not. This is based on anecdotal information from various sources including other forums and critical analysis of NEM 3.0. Also there is nothing about a battery installation that requires an IOU approval. It does require a building permit but since the battery typically does not sell or export to the grid it is not subject to a Net Energy Metering agreement. Two exceptions to that would be if you wanted SGIP funds or if you wanted to join a Virtual Power Plant.

My own risk assessment is that with a battery properly sized and programmed the downside cost of being forced into NEM 3.0 would be minimal, since the pricing of NEM 3.0 economically favors batteries. Even though it may seem wise to ask one of the IOUs about that question, I am not sure I would put much faith in the answer I received even it it was in writing. It is a risk I have taken by installing a battery without seeking permission from PG&E. To me the upside benefits far outweigh the downside risks.

I should add that my DIY cost was significantly less than the commercially available options in the marketplace. That could change the risk model for others. It may depend on where you are standing.

I presume your battery is set up so that it neither draws from nor sends back electricity to the grid? Because I think I read that if you charge your battery from the grid, then you can't get credit from sending power back to the grid. Then to review, your solar charges your battery and send electricity to your house. But if the grid goes down, then the solar will only charge your battery and will not directly send electricity to the house. And you will be isolated from grid during the blackout?

Thanks.

[OCJ]

The answer is right here in the decision: https://docs.cpuc.ca.gov/PublishedDo.../500043682.PDF

Page 169 of the PDF, page 166 of the decision.

[Ampster]

I presume your battery is set up so that it neither draws from nor sends back electricity to the grid? Because I think I read that if you charge your battery from the grid, then you can't get credit from sending power back to the grid. Then to review, your solar charges your battery and send electricity to your house. But if the grid goes down, then the solar will only charge your battery and will not directly send electricity to the house. And you will be isolated from grid during the blackout?
:

My hybrid inverter controls everything and is very flexible. I could draw from the grid and actually send battery energy to the grid. The latter would violate my NEM agreement because that hybrid is not listed in my NEM agreement. There is not limit as far as charging from the grid with my IOU since once the power comes through the meter I am free to do whatever I wish as long as it is legal. The limitation is that to take the Investment Tax Credit, the battery needs to be charged from solar. I keep logs in the event that I would be audited in the future.