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Update: Charge PowerWall from Grid

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There have been a few prior threads about grid charging, something several of us want to do. The gist is that Tesla does not enable grid charging for US solar installations except during Storm Watch events. But that just might be changing....

At my request, my installer put me in touch with his account manager inside Tesla. We talked about Tesla enabling grid charging for my PowerWall (which he confirmed is against current Tesla policy) and also about changing that policy.

He said that he agrees that grid charging would be a good feature, that it is normal outside the US, and that it is under serious discussion inside of Tesla. He expects the policy will be changed within a few months. The policy dates back to when pretty much every installation took the Income Tax Credit, so Tesla chose to avoid confrontations with IRS or confusion among customers. The situation has changed in several ways, so Tesla is reconsidering.

So, if you are interested in being able to charge from the grid, please contact your installer and/or Tesla and request that grid charging be enabled. Let Tesla know that some of us really want this capability. The more they hear this, the more likely they will respond.

SW
 
There have been a few prior threads about grid charging, something several of us want to do. The gist is that Tesla does not enable grid charging for US solar installations except during Storm Watch events. But that just might be changing....

At my request, my installer put me in touch with his account manager inside Tesla. We talked about Tesla enabling grid charging for my PowerWall (which he confirmed is against current Tesla policy) and also about changing that policy.

He said that he agrees that grid charging would be a good feature, that it is normal outside the US, and that it is under serious discussion inside of Tesla. He expects the policy will be changed within a few months. The policy dates back to when pretty much every installation took the Income Tax Credit, so Tesla chose to avoid confrontations with IRS or confusion among customers. The situation has changed in several ways, so Tesla is reconsidering.

So, if you are interested in being able to charge from the grid, please contact your installer and/or Tesla and request that grid charging be enabled. Let Tesla know that some of us really want this capability. The more they hear this, the more likely they will respond.

SW
I went through all of this with Tesla a year ago. Keep us informed but I am not holding my breathe
 
I went through all of this with Tesla a year ago.
ITC requrirement expires 5 years after claimed. In 2020, SGIP equity resiliency budget dropped $600 million on storage, i.e. 40,000 PowerWalls, potentially with no ITC benefit. All I'm saying is that it may be time to try again. Not for immediate approval, but to move Tesla's corporate attitude just a bit.

The political atmosphere is also ripe. Storage with grid and solar charging is the solution to the problem which NEM3 is proposing to solve - by killing all solar. With grid charging, solar or not, a PowerWall customer can completely avoid drawing from the grid during peak demand periods. I do.

The graph below lays out CPUC's justification for NEM3 in their "White Paper". The central idea is that solar does not keep folks off the grid during peak demand times. Maybe so, but batteries do. Tesla's solar is now sold only with PowerWall, and other storage systems (Enphase and LG) do support grid charging. So, gird charging is a win for battery owners, dramatically reduces costs for utilities (and thus for their non-sola customers as well), and sells Tesla and other's batteries. A win, win, win, win deal which even Tesla can not ignore.

So pester them again, please. This is about raising Tesla internal awareness.
 
It shouldn't be Tesla's responsibility to control whether or not individual taxpayers are doing their taxes correctly. That should be the responsibility of the individual.

What I'm curious about is how would a person deal with a situation where the ITC was used for only part of the storage. I had 2 Powerwalls installed without using the ITC. If I install a 3rd Powerwall and claim the ITC for it would I be allowed to charge my Powerwalls to 2/3rds of their capacity from the grid?
 
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There have been a few prior threads about grid charging, something several of us want to do. The gist is that Tesla does not enable grid charging for US solar installations except during Storm Watch events. But that just might be changing....

At my request, my installer put me in touch with his account manager inside Tesla. We talked about Tesla enabling grid charging for my PowerWall (which he confirmed is against current Tesla policy) and also about changing that policy.

He said that he agrees that grid charging would be a good feature, that it is normal outside the US, and that it is under serious discussion inside of Tesla. He expects the policy will be changed within a few months. The policy dates back to when pretty much every installation took the Income Tax Credit, so Tesla chose to avoid confrontations with IRS or confusion among customers. The situation has changed in several ways, so Tesla is reconsidering.

So, if you are interested in being able to charge from the grid, please contact your installer and/or Tesla and request that grid charging be enabled. Let Tesla know that some of us really want this capability. The more they hear this, the more likely they will respond.

SW
What is your motivation for wanting to do this? If you think that it will add additional savings, how are you calculating those savings because I am skeptical that there is much improvement even with the EV2-A rate plan that you are on.
 
Yes, I've never understood the logic of not wanting someone to charge storage during low demand periods and discharging it during high demand periods (other than lost utility profits).
Assuming that you are replying to my prior post I don't think that it is that simple, or at least it isn't with solar NEM rules.

The Powerwalls are being recharged in the early morning hours at the EV2-A Off-Peak rate of $0.2448, but then that same rate applies until 3:00pm so any excess solar is also credited at that same low rate which makes it mostly a wash except for the NBC charges. The OP also has a small amount, 3.65kW, of solar with two Powerwalls and is extremely likely to be a net kWh consumer which means that the generation charges on the imports (which are now higher) will be charged at true-up even if total credit is negative. If you are a net generator (both $$ and kWh) then the credit gets higher which is zero'ed out at true-up, but you imported more so your NBCs went up and that will cost you if the NBCs are more than your MDCs.

If the solar can't recharge the Powerwalls enough by 3:00pm to get through the higher Part-Peak and Peak periods from 3:00pm-12:00am then get a full charge from the grid to top them off should be cost effective.

If you are net generator (kWh) then this would

This is why I asked the OP what calculations they may have done. Maybe this is a win, but if it is I think it is a marginal win. For a non-solar account then it would definitely be a win.
 
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Assuming that you are replying to my prior post I don't think that it is that simple, or at least it isn't with solar NEM rules.

The Powerwalls are being recharged in the early morning hours at the EV2-A Off-Peak rate of $0.2448, but then that same rate applies until 3:00pm so any excess solar is also credited at that same low rate which makes it mostly a wash except for the NBC charges. The OP also has a small amount, 3.65kW, of solar with two Powerwalls and is extremely likely to be a net kWh consumer which means that the generation charges on the imports (which are now higher) will be charged at true-up even if total credit is negative. If you are a net generator (both $$ and kWh) then the credit gets higher which is zero'ed out at true-up, but you imported more so your NBCs went up and that will cost you if the NBCs are more than your MDCs.

If the solar can't recharge the Powerwalls enough by 3:00pm to get through the higher Part-Peak and Peak periods from 3:00pm-12:00am then get a full charge from the grid to top them off should be cost effective.

If you are net generator (kWh) then this would

This is why I asked the OP what calculations they may have done. Maybe this is a win, but if it is I think it is a marginal win. For a non-solar account then it would definitely be a win.
I wasn't responding to your post but more of a general statement regarding arbitrage.
If the utilities structured their rates to truly reflect their costs then it one should be allowed to charge their storage during low rate periods and feed their power back to the grid during high demand periods when it costs the utilities more for power. I'm not saying that someone should get paid what the utilities charge for power received but they should establish a payment rate consistent with what power costs from other sources. And I realize that there may be no incentive to send stored power back to the utilities under this scenario but the problem is the whole rate structure is artificial.
 
What is your motivation for wanting to do this?
You do ask an interesting question.

The flippant answer is that it saves me money and it saves PG&E money, and hence it saves our neighbors money too. Eliminating my share of peak period consumption is a good thing for everybody.

But your question does raise the issue of how much does it save.

The economics of battery storage have always been sketchy, and the savings from my time shifting would not economically justify a PowerWall. But SGIP paid for ours, so any savings represents an infinite ROI, as well as actual cash savings.

A couple of other details: I am grandfathered on NEM1, so have no NBCs. Also we have only one PowerWall which is adequate to get us through PSPS extended outages, at least during summer and fall months when those tend to happen.

Here is a rough cut at the economics. My reserve is set to 20%, and our partial and peak period consumption takes 50 - 80% of a full PW charge, or roughly half of my average daily consumption of around 15kWh. On average, off-peak costs $0.18 less than partial and peak. This means that time shifting saves me around $500 per year. (15 kWh * 365 * 50% * $0.18/kWh) This will really help offset charging our Model Y at home. Short sunlight and cloudy winter weather make it hard to charge this much on many days, cutting into my savings.

What is harder to know is how much does grid charging actually save. Having grid charged a lot last winter, it might be possible to calculate my exact savings, but I'm not sure I have the data I'd need. I'll think about this.
 
The flippant answer is that it saves me money and it saves PG&E money, and hence it saves our neighbors money too. Eliminating my share of peak period consumption is a good thing for everybody.

Just so I understand your situation; how may days last year did you experience where your solar was unable to charge your batteries to carry you through the peak time(s)? Will you really see much benefit grid-charging your Powerwalls?

Speaking of my own experience, I have a rinky dink solar array compared to most posting here on TMC (6.7 kWp AC). During the Spring and Summer, there was only one single day where I had to take 2 kWh from the Grid during the EV2A shoulder+peak time (3pm to midnight). So, there was no day in the Summer where grid-charging would have done me a large amount of good.

In the Winter, there were a few days where it was raining/cloudy. My home heating is from natural gas, so I don't have "peak time" to worry about for heating the home. But there weren't really that many days where grid-charging would have helped me out much. Maybe 30 calendar days in November to January was I dipping into peak and shoulder rates. So yeah, having grid-charging available in the winter would be awesome. But unfortunately winter-time peak-management isn't helping PG&E or the grid much.

Don't get me wrong, I'd love to grid-charge during the Winter on those 30 days. And if it isn't obvious by now I hate PG&E. But I don't really see a case that the grid benefits from me grid-charging Powerwalls in the Winter.

However, if your heating was electric, grid-charging in the winter would be super-beneficial assuming your solar array isn't the size of 6 football fields like h2ofun.
 
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one should be allowed to charge their storage during low rate periods and feed their power back to the grid during high demand periods
That is a bit off topic. Dumping stored power onto the grid is forbidden by utility interconnection rules and NEM tariffs, and not allowed by PowerWall or other consumer storage systems.

There are, as you propose, companies which do grid scale storage under tariffs as you describe. A large such plant was installed at Moss Landing on Montery Bay, and more going in around the world.

What you say about the present rate structure being artificial is true. But again a bit off topic. Large users subsidize smaller users. The old tiered plans charged high prices when you used more, letting air conditioning owners help pay for electric for those without. I think the point was to enable everyone to get connected, which is evidently a very good idea. Rural electrification was a huge goal, as universal high speed internet is today.

Grid charging a solar connected PowerWall allows one to stay off the grid during peak periods regardless of solar production limitations.
 
You do ask an interesting question.

The flippant answer is that it saves me money and it saves PG&E money, and hence it saves our neighbors money too. Eliminating my share of peak period consumption is a good thing for everybody.

But your question does raise the issue of how much does it save.

The economics of battery storage have always been sketchy, and the savings from my time shifting would not economically justify a PowerWall. But SGIP paid for ours, so any savings represents an infinite ROI, as well as actual cash savings.

A couple of other details: I am grandfathered on NEM1, so have no NBCs. Also we have only one PowerWall which is adequate to get us through PSPS extended outages, at least during summer and fall months when those tend to happen.

Here is a rough cut at the economics. My reserve is set to 20%, and our partial and peak period consumption takes 50 - 80% of a full PW charge, or roughly half of my average daily consumption of around 15kWh. On average, off-peak costs $0.18 less than partial and peak. This means that time shifting saves me around $500 per year. (15 kWh * 365 * 50% * $0.18/kWh) This will really help offset charging our Model Y at home. Short sunlight and cloudy winter weather make it hard to charge this much on many days, cutting into my savings.

What is harder to know is how much does grid charging actually save. Having grid charged a lot last winter, it might be possible to calculate my exact savings, but I'm not sure I have the data I'd need. I'll think about this.
One Powerwall makes more sense with a 3.65kW of solar, I was reading your signature has have two PWs instead of one PW2. One place to start is with your last true-up:
  • What was the final cumulated charge/credit amount?
  • What was the total imported kWh?
  • What was the total exported kWh?
  • What was the balance due after your monthly MDC were subtracted?
 
That is a bit off topic. Dumping stored power onto the grid is forbidden by utility interconnection rules and NEM tariffs, and not allowed by PowerWall or other consumer storage systems.
This isn't an abnsolute, but it is strongly discouraged by PG&E and SDG&E with IOUs in other states actively encourage time shifting exports. Even with PG&E this isn't forbidden, but it is restricted by limiting the amount of exports allowed to the estimated amount that the solar array can produce during the billing period. Then there was the recent Tesla Virtual Power Plant, VPP, beta in 2021 in which you could opt-in to allowing Tesla/PG&E to force exporting from your Powerwall.
 
how may days last year did you experience where your solar was unable to charge your batteries to carry you through the peak time(s)
Oh! You just brought out the importance of getting Tesla to support grid charging!

It needs to be automatic so you don't have to watch the weather to know if you need to grid charge or not.

The answer to your question is that I don't know how many days I din't have enough solar. What I did was grid charge every night after midnight so our PW was full every morning. All our solar when to the grid, and the PW ran the house every day from 3 to midnight, our peak times. We are on NEM1, so there is no NBC penalty for the round trip, only the same few% loss in the PW itself.

I wrote little script to set PW reserve at 100% at night, and 20% in the morning. But a better implementation might let solar charge and only supplement when the charge state requires faster charging to get to 100% before the rates rise.

Anyway, when grid charging is in the software, one does not need to pay attention. When it is not in software, it requires daily decisions, assuming one knows how to do it at all.

Tesla enabling grid charging would solve both problems.

If you are wondering how much I actually saved, as I said, I don't know. But it was under $500 for sure. Maybe $100. I may be able to figure an exact number if you need it.

I tried to post CPUC's chart of costs and solar production. But even during winter, peak periods require more generation be online than off peak. They claim their average cost is like 6X higher during peak, winter and summer. Essentially most of their costs come during only a few hours each day. So staying off grid during winter is still valuable. To put it another way using PG&E rates as a proxy for their costs, EV2-A is currently on their winter pricing at 25¢ off-peak and 41¢ to 43¢ peak. Summertime peak is 56¢. So, winter peak is bad, but not as bad a summer. Night time is baseline power, plenty of excess with most of the air-conditioning and industrial use shut down.
 
I did a reconciliation on my last true-up and one of the things I calculated was the incremental cost of Winter Part-Peak and Peak energy that was not covered by my Powerwalls time shifting my solar. In the end, I could save almost $200 by grid charging during Off-Peak and avoiding Part-Peak and Peak charges in the Winter. At the time I was calculating it, I was considering buying some hardware to DIY a battery grid tied inverter to supplement my Powerwalls. For that case, it wasn't worthwhile. However, if I could grid charge my Powerwalls, I would certainly avail myself of that feature after my 5 year ITC requirement runs out. Tax year 2023 is clear! LFG!

Grid Charge Estimate.jpg
 
What I did was grid charge every night after midnight so our PW was full every morning. All our solar when to the grid, and the PW ran the house every day from 3 to midnight, our peak times. We are on NEM1, so there is no NBC penalty for the round trip, only the same few% loss in the PW itself.


I'm confused... I thought you wanted to grid charge but couldn't? How did you grid charge a solar-paired Powerwall every night and have 100% full Powerwall by sun up?
 
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I'm confused... I thought you wanted to grid charge but couldn't? How did you grid charge a solar-paired Powerwall every night and have 100% full Powerwall by sun up?

No, that user can grid charge by changing the setup in the installer options. If this discussion starts going that direction, however, I am going to lock the thread. I am answering so that @swedge doesnt feel compelled to answer that, and I am also directing discussion away from that.
 
No, that user can grid charge by changing the setup in the installer options. If this discussion starts going that direction, however, I am going to lock the thread. I am answering so that @swedge doesnt feel compelled to answer that, and I am also directing discussion away from that.
Since tesla sees EVERYTHING that happens in the GW, losing warranty is not worth it to me!!!
 
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