The real answer is it doesn't. There are other threads going into more detail, but the short of it is the IRS, in a private letter ruling - https://www.irs.gov/pub/irs-wd/201809003.pdf (which officially means it does not establish precedent,) stated that PWs could claim the credit, but only because the taxpayers stated that 100% of stored energy came from the sun. The IRS went into some detail to note that Congress had used a 50% rule elsewhere but omitted it here, so 100% was the rule. This means that potentially any use of storm watch could actually invalidate the credit. I think the assumption is that because it is generally expected to be a very minimal amount (though folks in CA fire country may not feel that way after this year) and is intended to assist with emergency conditions, it is probably something that can slide (and the customer is largely not in control of when it happens.)
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Can Powerwall be charged from grid in backup-only mode?
- Thread starter Dboy
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CrazyRabbit
Active Member
EMF
Member
@wjgjr - That was an incredibly useful piece of information. I now understand why the system is set up so that it cannot charge from the grid if connected to solar, and still be eligible for the federal tax credit. And yes, @CrazyRabbit, I now understand the federal tax credit is only available because the Powerewall is part of a "solar electric property expenditure." All good information.
I also found the very useful thread here, which describes the restrictions imposed by the California Public Utility Commission (PUC):
How to charge powerwalls from grid with solar
The current implementation by Tesla is apparently more restrictive than it has to be to meet these requirements (but needed if you want the federal tax credit).
Unfortunately, these factors limit the utility and cost effectiveness of the Powerwall and residential energy storage, in general. I'm not trying to game the system for profit here, I'm just trying to minimize my use of fossil energy. As noted in this thread and in the one referenced above, there is abundant renewable energy during non-peak daylight hours here in California, even in the winter when my system is completely shaded. During Peak hours, we have to augment those sources with fossil fuel (methane, coal) power. If I could shift my consumption to those off-Peak hours by charging the Powerwalls from the grid at those times and then using that stored energy during Peak hours, I could help to even the overall load (reducing the cost to the power company as well as my own cost) while using more renewable energy. I would also have a reliable backup system in the event of inevitable power outages. That would make residential energy storage a more practical option. Oh well....
Thanks for all your help!
I also found the very useful thread here, which describes the restrictions imposed by the California Public Utility Commission (PUC):
How to charge powerwalls from grid with solar
The current implementation by Tesla is apparently more restrictive than it has to be to meet these requirements (but needed if you want the federal tax credit).
Unfortunately, these factors limit the utility and cost effectiveness of the Powerwall and residential energy storage, in general. I'm not trying to game the system for profit here, I'm just trying to minimize my use of fossil energy. As noted in this thread and in the one referenced above, there is abundant renewable energy during non-peak daylight hours here in California, even in the winter when my system is completely shaded. During Peak hours, we have to augment those sources with fossil fuel (methane, coal) power. If I could shift my consumption to those off-Peak hours by charging the Powerwalls from the grid at those times and then using that stored energy during Peak hours, I could help to even the overall load (reducing the cost to the power company as well as my own cost) while using more renewable energy. I would also have a reliable backup system in the event of inevitable power outages. That would make residential energy storage a more practical option. Oh well....
Thanks for all your help!
Hopefully Tesla will start doing a better job of offering more options to consumers - I think they are currently rigid because it is much easier for them, since there are not only federal ITC implications but utility rules involved. It seems some utilities don't really care how you use your PWs (and the example of the person in the US who got Tesla to unlock their PW got their utility to put in writing they were fine with it) while other utilities have very strict rules about how PWs can interact with the grid.
But, with the ITC currently scheduled to go away in just over a year and people getting 5 years into their solar+PW installs (which seems to be the point at which you could re-purpose or scrap your system without having to pay back the credit,) I think the demand for more flexibility in PW charging and/or discharging is going to grow.
But, with the ITC currently scheduled to go away in just over a year and people getting 5 years into their solar+PW installs (which seems to be the point at which you could re-purpose or scrap your system without having to pay back the credit,) I think the demand for more flexibility in PW charging and/or discharging is going to grow.
We have solar and Powerwalls and they allow us to minimize our use of fossil energy. Since the weather is clear often (too often?) here in California you can go for long stretches without using any power from the grid. The 2 Powerwalls we have are enough to carry us through the night and the day's solar is enough to power the house and recharge the powerwalls.
aesculus
Still Trying to Figure This All Out
You cannot really buy 100% solar just by paying more unless there is a dedicated distribution line from the solar farm to your house. It may make you feel good, but if you are on a utility grid, your electricity can come from any generation source on that grid
aesculus
Still Trying to Figure This All Out
True. But this is just an accounting issue anyway so the claim can hold up. The user was basically paying someone to produce solar energy and he was taking only that much power from the grid. So on paper he was buying pure solar power.
As a side note: I once found a company that claimed they could track every electrical charge from source to sink.
True. But this is just an accounting issue anyway so the claim can hold up. The user was basically paying someone to produce solar energy and he was taking only that much power from the grid. So on paper he was buying pure solar power.
As a side note: I once found a company that claimed they could track every electrical charge from source to sink.
On paper only and certainly not at night. and, what if more people sign up for that than the solar farm produces?. Utility just pockets extra profits
I would not think that last part is true - at least in MD. I don't think they can over-sell, as it is competitive suppliers who offer this, and they are obligated to deliver the amount of power that matches what they have sold. (I think most offer renewables, not just solar, which addresses solar at night, but I honestly do not know if they can meet their obligations by providing X amount of power over a day or longer timeframes.)
It is certainly true that it is a paper exercise in the sense that all the power is commingled, and I would also guess that unsold renewables are just sold into the utility at the standard wholesale rate. But, if enough people express interest, it would force building more renewables in order to capture more of that market, so it is not meaningless. I can't say how effective it is compared to other options for transitioning to renewables (including everything from the federal incentives to state REC programs to outright mandates) but it is a way for consumers to direct their utility generation expenses to suppliers who provide green power.
At least in MD, they sell in terms of percent "renewables", so a cloudy day may be offset by other options. And my guess is that if necessary, they make it up by over-supplying the market on other days (and may pay some penalties to the utilities they shorted for those days.) Just like with home solar, there are obviously limits to this, and there will be a need for storage solutions, like batteries or pumped storage, but it is still a tool. Also, there are third-party companies that certify these suppliers are actually providing what is promised, and you can make sure to sign up with a company that is properly certified.
RKCRLR
Active Member
So it appears that is is not a PG&E requirement to disallow charging PowerWalls from the grid if you have solar, it is a Tesla requirement.
I had asked the PG&E solar department about this. They said I needed to contact the SGIP department. I emailed the SGIP department and asked:
"Is it a PG&E requirement that I'm not allowed to charge my Powerwalls from the grid if I have solar generation?"
SGIP answered:
"Thanks for reaching out to us. You may charge your battery from the grid."
I had asked the PG&E solar department about this. They said I needed to contact the SGIP department. I emailed the SGIP department and asked:
"Is it a PG&E requirement that I'm not allowed to charge my Powerwalls from the grid if I have solar generation?"
SGIP answered:
"Thanks for reaching out to us. You may charge your battery from the grid."
Merrill
Merrill
I remember the comment, just because someone from the IRS told you something, does not make them right.
RKCRLR
Active Member
I would suggest attempting to get PGE to send you something on their company letterhead stating that, "Yes, you can charge from the grid while connected to PGE and also setup with net metering solar".
If that is what they told you "yes" to, then they should be willing to send it to you in writing. if they do that (I doubt they will, but if they do), then you take that document and ask tesla to enable it for you.
Failing that, tesla isnt going to enable grid charging for you while you are connected to solar, regardless of what you got in an email.