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PowerWall Without Solar?

HankLloydRight

No Roads
Jan 18, 2014
12,899
10,910
Connecticut
Now I’m thinking of adding four more panels on the small side roof sections for 30 panels total to absolutely maximize the solar potential.
 
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swedge

Member
May 12, 2020
67
53
Oakland, CA
Absolutely. Free (so referral, or equity and resilliency) makes a ton of sense. Does that plan also help with solar?
SGIP has incentives for renewable generation and energy storage systems. Fuel cells, bio-gas, wind turbines, and batteries are examples. Not solar, though, as far as I know. Feel free to google it, however be warned - the "handbook" for the program is over a hundred pages of jargon.
 

swedge

Member
May 12, 2020
67
53
Oakland, CA
Great, thanks Brett for that explanation.
I agree, good explanation Brett!

Hank, I think you answered my original question, that PW with no solar can charge off the grid in a Time-Based mode, though I gather you have not actually tried this. I do wonder when it would charge, probably as soon as off-peak period starts.

Here is a strange idea: What would happen if you don't take the income tax credit on the batteries, and connect them as if you had no solar, perhaps by tying the solar in on the grid side of the Gateway. Running PWs in the Time-Based Cost Saving mode, they'd charge from the grid off peak, and discharge to the house during peak times. One disadvantage would be that PWs would not keep your solar alive during an extended outage, but they would back you up for as long as they can.

But one thing is clear from this discussion: each owner is in a different boat. Rate plans, net metering rules, usage patterns, location, roof orientation, shade from neighbor's trees, all these vary, and each affects what options are best.
 

HankLloydRight

No Roads
Jan 18, 2014
12,899
10,910
Connecticut
Here is a strange idea: What would happen if you don't take the income tax credit on the batteries...

Since I'm not paying for either battery (they were referral program awards), I'm not claiming the ITC on them, only the solar install.

But even still, to do what you propose would require an electrician to re-wire the PWs into a non-supported configuration, so I don't know how the Tesla integration/app would work in that case.

But it does raise another interesting question. What if I had one PW only charge from solar, and the other PW only charge from the grid? That would be the best of both worlds*, but I'm pretty sure Tesla would not engineer nor install it that way.


* PW1 would likely fully charge to 100% from solar from dawn to 12pm, and PW2 would charge to 100% from grid during the same time period. That way, I'd have 27kWh to use during the peak 8 hours (plus what solar delivers) with the remainder to use up the rest of the day/evening. Repeat. I'll have to ask Tesla if the can engineer it that way.
 

BrettS

Active Member
Mar 28, 2017
2,109
2,512
Orlando, FL
You can certainly ask, but I think the chance of tesla doing something like that are 0%. One of the big problems is that in a system with multiple powerwalls the powerwalls are not individually controllable. They just appear as one large virtual powerwall with a bigger battery. The only way to get individual control would be to have each powerwall as part of a totally separate system with it’s own gateway (TEG). But that would mean that you would either need to divide up your circuits and put some circuits behind one TEG and other circuits behind the other TEG or somehow cascade the TEGs (which I don’t believe is a supported configuration at all).

Additionally, either way, this would then result in you having two single powerwalls instead of having a pair of powerwalls and that would come with with all of the limitations of a single powerwall install... you would be looking at a partial home backup solution and you would be unable to backup any larger (more than 30A) circuits.

And even with all the technical limitations aside, it’s my understanding that Tesla simply refuses to allow a powerwall that is installed on a site with solar to charge from the grid at all, whether the tax credit is claimed or not.
 
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jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,216
9,063
Riverside Co. CA
Thanks. Just to confirm, it is technically possible to charge the powerwalls from the grid and/or solar as needed, say in other countries?

Other countries do this, yes. It is certainly not a technical limitation, because we charge from the grid as well during tesla triggered stormwatch mode, so its not a "wiring" thing. Its a policy thing. One person here managed to get tesla to allow grid charging with solar by getting his utility to give him a letter on their on letterhead that it was specifically allowed.

I forget what state they were in, though. nevertheless, its really not done here whether you take the tax credit or not, and I would consider any request to charge from the grid at customer triggering (ie non stormwatch) pretty much a dead end if that person has solar / pv.
 

HankLloydRight

No Roads
Jan 18, 2014
12,899
10,910
Connecticut
. One person here managed to get tesla to allow grid charging with solar by getting his utility to give him a letter on their on letterhead that it was specifically allowed.

I'll definitely pursue the letter from the power company avenue. Thank you.

350.png
 

wjgjr

Active Member
May 11, 2020
1,168
912
Silver Spring, MD
Other countries do this, yes. It is certainly not a technical limitation, because we charge from the grid as well during tesla triggered stormwatch mode, so its not a "wiring" thing. Its a policy thing. One person here managed to get tesla to allow grid charging with solar by getting his utility to give him a letter on their on letterhead that it was specifically allowed.

I forget what state they were in, though. nevertheless, its really not done here whether you take the tax credit or not, and I would consider any request to charge from the grid at customer triggering (ie non stormwatch) pretty much a dead end if that person has solar / pv.
It is going to be interesting to see if and how this might change over the next several years as more batteries are deployed, more people roll off the 5-year ITC lock on non-solar charging, and the ITC potentially goes away for new installs. I understand utilities are often opposed to it, but using batteries to provide additional time-shifting of loads makes a lot of sense for reducing peak demand and I could see states doing more to require utilities to incentivize customers to charge batteries overnight and then discharge them during (typically evening) peak times.
 
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jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,216
9,063
Riverside Co. CA
I'll definitely pursue the letter from the power company avenue. Thank you.

350.png


Lol! I am going from memory, but I believe it was a person in Arizona, whose utility company specifically allowed charging from the grid while connected to solar or something. It was in the utility companies information I believe. They went back and forth with tesla and finally got it turned on, but there was only that one instance that I am aware of. it was posted here in this section though, so maybe you could find the discussion if you dig for it here somewhere.
 
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HankLloydRight

No Roads
Jan 18, 2014
12,899
10,910
Connecticut
Here at my new house, I need to replace three aging thermostats. My elect utility has deeply discounted Nest E thermostats for $69/each (limit: 3). I ordered three. In addition, they offered an additional $25 off EACH unit (net cost $44/each) to join their power reduction plan during peak usage times, where they will announce and automatically turn down my thermostats to reduce the overall load on the grid. I can manually override this turn-down if I want to.

Given this (and other peak power reduction incentives) I can't see why they would be opposed to grid-charging batteries off-peak for on-peak usage.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,216
9,063
Riverside Co. CA
It is going to be interesting to see if and how this might change over the next several years as more batteries are deployed, more people roll off the 5-year ITC lock on non-solar charging, and the ITC potentially goes away for new installs. I understand utilities are often opposed to it, but using batteries to provide additional time-shifting of loads makes a lot of sense for reducing peak demand and I could see states doing more to require utilities to incentivize customers to charge batteries overnight and then discharge them during (typically evening) peak times.

I get the load shifting, but what likely does not make sense to them is everyone saying to them (utility) "hey utility, I want to buy this widget from you at 10 cents in the middle of the night, hold onto it for 15 hours, then sell this same widget back to you for 40 cents at 4pm, and I want to buy the widgets in bulk. You are ok with that, right?"

In effect, people wanting to charge the powerwall from the grid during a cheap / off peak rate, then either discharge the powerwall into the utility at peak rates (effectively selling it to the utility for more than they bought it) or selling their solar power to the utility at peak rates while they use the cheap power "they bought from the utility", doesnt make much sense financially.

The utilities want to encourage self consumption, not encourage people to become mini utilities and try to actually make money off selling their power. Thus the "store your OWN power and self consume it during peak rates, dont try to sell it to me at peak rates", dance of the utilities changing peak times from 12-8 in california (prime solar generation time) to 4-9 or 5-8 (when they can assure themselves that solar generation is winding down).

Its going to be interesting to see how this shakes out, for sure, but it doesnt make sense for any business to sell you something for a dime, then buy it back from you for 20 cents to 50 cents (depending on utility) basically the same day and perform those transactions in bulk, losing 10 cents to 40 cents on each widget (kWh).
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,216
9,063
Riverside Co. CA
Here at my new house, I need to replace three aging thermostats. My elect utility has deeply discounted Nest E thermostats for $69/each (limit: 3). I ordered three. In addition, they offered an additional $25 off EACH unit (net cost $44/each) to join their power reduction plan during peak usage times, where they will announce and automatically turn down my thermostats to reduce the overall load on the grid. I can manually override this turn-down if I want to.

Given this (and other peak power reduction incentives) I can't see why they would be opposed to grid-charging batteries off-peak for on-peak usage.

They will reduce your home load by turning off your thermostat, that is not the same thing as you selling them power for 2 times to 4 times more than you just bought it from them for. its my opinion that the reason "without solar" you can charge from the grid, is that you have to discharge the powerwall into your home during peak times to avoid them (so are not attempting to sell them power at more than you bought it for).

Without solar (or some other power generation onsite that is non utility) you have to consume your own power during peak, which is what they want.. reducing your load on the utility, not selling them power for more than you bought it for. WITH solar, if you charge off peak, you would be using your powerwall on peak... AND selling them power for more than you bought it for, which they do not want for obvious reasons.
 

wjgjr

Active Member
May 11, 2020
1,168
912
Silver Spring, MD
Here at my new house, I need to replace three aging thermostats. My elect utility has deeply discounted Nest E thermostats for $69/each (limit: 3). I ordered three. In addition, they offered an additional $25 off EACH unit (net cost $44/each) to join their power reduction plan during peak usage times, where they will announce and automatically turn down my thermostats to reduce the overall load on the grid. I can manually override this turn-down if I want to.

Given this (and other peak power reduction incentives) I can't see why they would be opposed to grid-charging batteries off-peak for on-peak usage.
Even if your utility is not concerned about the money side (assuming TOU rates, a utility obviously loses money with such a scheme) I'm guessing there is still a concern about control. I don't know if your utility is the one (or like the one) somebody else in CT mentioned that has the program to discharge batteries during peak times to manage the load, but that program seems to be a very defined one in that it happens automatically based on specific criteria.

At least here in MD, it seems pretty clear that most of the "green" programs the utilities offer really come from mandates from the PSC and are offset by higher charges elsewhere (since the profit margins are regulated/reviewed along with rate changes proposed by the utilities.) The utilities themselves are not particularly interested in things being green, so much as how it affects the bottom line. (Even their reputation probably isn't a major concern given they are legal monopolies, at least on the transmission/distribution side.) That is why I said in a prior post that I think a lot of these changes will need to be initiated by states/state regulators who can require utilities to structure their rates and rules to incentivize greener technologies.
 

HankLloydRight

No Roads
Jan 18, 2014
12,899
10,910
Connecticut
I see your point, but it's not selling it back to them at the peak rates for significanly more than what I paid for it. It's only denying the utility the delta between the on-peak and off-peak rates. They're doing everything they can do get people to use less peak power. I don't see this as any different.

Also, here in CT when I sold my last house with solar, I ended up with a small net credit of kWh from net-metering. The regular residential rate for power at that time was $0.19/kWh. They 'bought back' that net metering credit at $0.03/kWh to close out my account. This is a regulated rate by ISO New England (oversees/regulates all New England utilities).
 

BrettS

Active Member
Mar 28, 2017
2,109
2,512
Orlando, FL
he load shifting, but what likely does not make sense to them is everyone saying to them (utility) "hey utility, I want to buy this widget from you at 10 cents in the middle of the night, hold onto it for 15 hours, then sell this same widget back to you for 40 cents at 4pm, and I want to buy the widgets in bulk. You are ok with that, right?"

The question is, how much is it costing the utility to make the widgets and how much profit are they making on it? It you think purely in terms of load shifting, you are asking to buy the widget at 10 cents at 3AM when it’s cheaper to make the widget so the utility makes their 3 cent profit. Then you are going to not buy the same widget at 3PM when it costs 40 cents. But it costs more to make the widgets at 3PM, so the utility would have only made the same 3 cents on that widget anyway. You’re still buying one widget and the utility is still making their 3 cents, it’s just a matter of buying the widget when it is cheapest.

I can see how the utility would be against arbitrage, but just load shifting isn’t so bad for the utility.
 

wjgjr

Active Member
May 11, 2020
1,168
912
Silver Spring, MD
I get the load shifting, but what likely does not make sense to them is everyone saying to them (utility) "hey utility, I want to buy this widget from you at 10 cents in the middle of the night, hold onto it for 15 hours, then sell this same widget back to you for 40 cents at 4pm, and I want to buy the widgets in bulk. You are ok with that, right?"

In effect, people wanting to charge the powerwall from the grid during a cheap / off peak rate, then either discharge the powerwall into the utility at peak rates (effectively selling it to the utility for more than they bought it) or selling their solar power to the utility at peak rates while they use the cheap power "they bought from the utility", doesnt make much sense financially.

The utilities want to encourage self consumption, not encourage people to become mini utilities and try to actually make money off selling their power. Thus the "store your OWN power and self consume it during peak rates, dont try to sell it to me at peak rates", dance of the utilities changing peak times from 12-8 in california (prime solar generation time) to 4-9 or 5-8 (when they can assure themselves that solar generation is winding down).

Its going to be interesting to see how this shakes out, for sure, but it doesnt make sense for any business to sell you something for a dime, then buy it back from you for 20 cents to 50 cents (depending on utility) basically the same day and perform those transactions in bulk, losing 10 cents to 40 cents on each widget (kWh).

I agree that this is an issue, particularly as the number of people with batteries increases. However, in some ways, it is really no different from the ongoing discussions regarding net metering in CA and elsewhere. Whether I have energy imported into the grid to a battery (that I bought overnight at a rate giving the utility its normal profit) or generated by solar, there is an opportunity to sell it to the utility at some later point.

The real issue is what should this rate be. It is clear that full net metering does not make sense as the long-term answer. However, there may still be a price point where the customer makes some money time shifting and the utility gets power at a lower rate than they would by turning on peaker plants. Additionally, reducing/avoiding these plants creates a public good by reducing pollution (assuming the peakers are the worst polluters.) For the consumer, the additional benefit is having access to backup power if needed, while the utility does not need to spend capital on so many of its own battery farms. Obviously, finding the right way to balance all of this is a challenge, but I think it should be possible, recognizing that at some future time there could come a point where incentives disappear because the battery capacity is sufficient to eliminate the peaks entirely.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,216
9,063
Riverside Co. CA
I see your point, but it's not selling it back to them at the peak rates for significanly more than what I paid for it. It's only denying the utility the delta between the on-peak and off-peak rates. They're doing everything they can do get people to use less peak power. I don't see this as any different.

Also, here in CT when I sold my last house with solar, I ended up with a small net credit of kWh from net-metering. The regular residential rate for power at that time was $0.19/kWh. They 'bought back' that net metering credit at $0.03/kWh to close out my account. This is a regulated rate by ISO New England (oversees/regulates all New England utilities).

it actually is selling to them for more than you paid, though, if you want to either discharge power you bought from them at off peak rates during peak times back to them, or, discharge ALL your solar to the utility, because you can run your home off batteries you filled by buying from them at cheap rates.

In both cases you are buying from them at off peak rates, then selling to them (getting a credit for) peak energy. From a business perspective it doesnt make any sense. What does make sense, is each individual home owner self consuming their OWN power, reducing the need to either build more power plants, or re start power plants etc.

Without solar, buying power at cheap rates and discharging INTO YOUR HOME during peak rates (reducing load on the utility) makes sense to both the home owner and them.

With solar, filling your batteries, as well as running your home with your OWN power (not bought from them at all) makes sense in reducing your load, and running your home during peak times with that same power you generated during the peak by discharging your battery into your home makes sense. They likely dont like buying power at peak rates at all (even solar) which is why, in california at least, peak times were changed to 4pm to 9pm or 5pm to 8pm.

I expect as more solar gets installed around the country, more utilities will follow suit and change peak time to 4pm to 9pm to ensure they are not buying much power at peak rates. Powerwalls will make sense to time shift ones own power. I dont think many utilities will sign up to allow someone to buy at 10 cents in the middle of the night, and sell back to them at 40 cents during peak, which is what people are asking for.

Oh @HankLloydRight you might be able to get grid charging if you agree not to export ANY energy at all. I think Hawaii is like that, some of our hawaii members could confirm. That also avoids the problem I was talking about. If you are not allowed to export any energy at all, the utility doesnt have to worry about you trying to sell them the widget for 30 cents when you bought it from them 10 hours ago for 10 cents, It would be just you self consuming your own energy + any you need from them, and in that case they likely will allow you grid charging.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,216
9,063
Riverside Co. CA
Its an interesting discussion, for sure, and its kind of nice to have it without a lot of the angst that generally goes along with this discussion. Its not like I am advocating for utilities (lol) I dont work for one or anything.

At some point, I feel like net metering will go away but the Utilities will incentivize battery + powerwall. In effect, "You self consume as much of your own power as you can generate, dont export to us, but we will give you incentives to make as much of your own power as you can, reducing load on our services".

I feel we are headed that way, but not sure how long it will take to get there.
 

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