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Charge powerwall from grid and solar?

I am hoping to have my site survey done soon. What is not clear to me at the moment is whether I can charge the battery from both the Grid and excess solar? I have a small solar panel that does not have enough overcapacity to fully charge the powerwall. Can I top it up at night from the grid?

Is this may be different in different regions depending on what your utility company allows?

Paul in Chicago.
 
I don't believe that Tesla allows any US customers to charge from the grid. The justification is that eligibility for the Federal tax credit requires charging from a renewable source only. Some people on this board were trying to get around this by not claiming the credit, but I haven't heard any success stories of being able to convince Tesla to change the configuration to allow grid charging.
 
Actually, the ITC applies to Powerwalls even if added to an existing solar installation. See https://www.nrel.gov/docs/fy18osti/70384.pdf

In particular:
NREL assumes that energy storage added to an existing renewable energy system would be eligible for the same benefit as a new system (see graphic above), based on a precedent set by a 2012 private-letter ruling5 that allowed a wind farm owner to add energy storage to an existing wind farm and claim the tax benefit. The PV and energy storage would need to be in close proximity and under common ownership (the same taxpayer).
 
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Reactions: Dave EV

KSilver2000

Active Member
Dec 23, 2017
1,368
2,438
CA
There is no Federal tax credit when you buy powerwalls as an add on to an existing solar installation.

False. The only way to get FITC for a PW is if you install it with an already existing PV system or concurrently with a new PV system. You don’t get the FITC if you install without any PV system as you’ll be charging from the grid then. The PW must charge 100% from PV (so size accordingly) to get FITC.
And regarding the PW, Tesla programs it so that the PW will only charge from PV if you have one. Cannot charge from both grid and PV as you wish to take advantage of TOU rate differences.
 
In my case, I purchased two Powerwalls back in 2017. No PV, just Powerwall,. You don't get ITC for just Powerwall. I was able to charge the Powerwall from grid in this case.

In 2018, I purchased PV from Tesla, and did get the ITC Tax Credit, and the Powerwall would not charge from grid.
In 2019, I added a third Powerwall, and this Powerwall acts just like the original one, will not charge from grid. The reason is that someone said that ITC has a 5 year life, so regardless of how many Powerwall I get after the fact, the 5 year for ITC still applies, which means I won't be able to charge the Powerwall from the grid for those 5 years...
 
My question about all this is who flips the switch to allow grid charging and how? Is it my installer or Tesla? Can i do it myself somehow?

Such a shame not to be able to suck up some of that nuclear baseload in my backyard and then power the house from it all day while I send solar to the grid. *sigh*. My plan would save GHGs and my money and do a favor for the grid but, noooo Tesla won’t allow it? Madness. Needs to change. Who do I talk to there? Lol. I’m serious, this is pretty indefensible for them to do. Regardless of the federal tax credit. That’s between the customer and the government.
 
My question about all this is who flips the switch to allow grid charging and how? Is it my installer or Tesla? Can i do it myself somehow?

Such a shame not to be able to suck up some of that nuclear baseload in my backyard and then power the house from it all day while I send solar to the grid. *sigh*. My plan would save GHGs and my money and do a favor for the grid but, noooo Tesla won’t allow it? Madness. Needs to change. Who do I talk to there? Lol. I’m serious, this is pretty indefensible for them to do. Regardless of the federal tax credit. That’s between the customer and the government.

normally there need to be a severe condition to allow you to charge from the grid if you have PV. National Weather Service severe alerts along with power company outages also are used for Tesla to turn on the Storm Watch feature.

Unfortunately the feds do limit charging from grid if you own PV when you apply for the ITC 30% credit. The power companies force Tesla to comply with this, and I believe the power companies can get data from Tesla for compliance checks.

I wish you the best to try and get the ruling changed. I wish it was different.
 

bkp_duke

Well-Known Member
May 15, 2016
6,591
28,226
San Diego, CA
There is no Federal tax credit when you buy powerwalls as an add on to an existing solar installation.

Is that really the only reason why they disabled that feature? That is a huge shame.

SO not true. You can deduct the 30% ITC if it is paired with an existing solar system. I did, and my CPA verified that this is correct.

Regarding charging from the grid when you have PV installed - Tesla LOCKS the firmware on these so that it will not charge from the grid in this circumstance. You must charge from PV.

As others pointed out, the rare exception is StormWatch, but again that is rare.

Also, no one has "tricked" the system to bypass the charge from PV requirement, so if you are looking for a work-around, there is not one.
 
I don't believe that Tesla allows any US customers to charge from the grid. The justification is that eligibility for the Federal tax credit requires charging from a renewable source only. Some people on this board were trying to get around this by not claiming the credit, but I haven't heard any success stories of being able to convince Tesla to change the configuration to allow grid charging.
My electricity from the grid is from renewable sources. Anyone with a similar setup able to get their Powerwall charged from the grid?

Choose to upgrade to GreenPrime, SVCE’s 100% renewable generation service, and be at the forefront of our community’s commitment to a clean energy future. GreenPrime is generated from 100% renewable, carbon-free sources, primarily from solar and wind farms in California and on the western grid.​
 
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jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
6,559
4,467
Northern California
My electricity from the grid is from renewable sources. Anyone with a similar setup able to get their Powerwall charged from the grid?

Choose to upgrade to GreenPrime, SVCE’s 100% renewable generation service, and be at the forefront of our community’s commitment to a clean energy future. GreenPrime is generated from 100% renewable, carbon-free sources, primarily from solar and wind farms in California and on the western grid.​
My guess is the company selling you the power is already getting tax credits and other subsidies,so you would not be eligible. If you become a producer by installing solar/wind at your home you can get the credit.
 
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Here’s a twist on that question. Can you ‘nest’ one Powerwall and Gateway within another Powerwall and Gateway?

I have a Powerwall and Gateway set to charge from the grid during off-peak (8 am to 4 pm when solar PV excess can be a regional problem) and then power critical house loads on-peak (4 pm to 9 pm when the PV is gone but air conditioning demand is still present). This is under California’s SGIP program. No power back to the grid. Works like a charm daily with about 1/2 to 2/3 of Powerwall capacity (and during power interruptions, like this infernally hot weekend in Los Angeles).

I do have some PV panels currently grid-tied upstream of the Gateway and Powerwall. These shut off if the main grid goes down. Could a second Gateway and Powerwall be installed at the main panel with the PV rewired to charge the second Powerwall? The second Gateway will only see the total house load (which includes the first Gateway and Powerwall). The second Powerwall would be set to Self-powered Mode with a high reserve (I don’t have space for enough PV to fully recharge a Powerwall in one day).

Would it work as I envision? Would an authorized installer agree to such a configuration? Thank you for any thoughts.
 

gpez

Member
Apr 25, 2019
794
658
USA
Would it work as I envision? Would an authorized installer agree to such a configuration? Thank you for any thoughts.

IANA electrician or authorized installer, my layperson answers are "probably" and "probably not".

Theoretically you could have an unlimited number of microgrids nested inside of each other so you could likely have Powerwalls "behind" each other. The app likely doesn't support this configuration and you'd want them controlled separately anyway so if you were able to do it you'd need two Tesla accounts.

Even though I think it's possible I'm not sure that a) Tesla would allow it or b) an installer would want to do it. Both are likely solvable if you had enough $ to throw at it.

I'd probably ask why go through the trouble rather than getting more Powerwalls and moving them to the solar side? You'd need to have enough Powerwalls for the whole house to support it off-grid anyway, at that point you're just duplicating systems. I'm not familiar with SGIP so if that's the reason I'd love to learn more.
 
Would it work as I envision?
If you have two separate Gateways, each with their own CT sensors, and there is any load being measured by both Powerwalls, unusual behavior could result. Depending on how you have each Gateway configured, they could both decide to offset the same load at the same time, so you'd be net exporting from the Powerwalls.

If you segregate your loads between the two Gateways, this problem is avoided, but that introduces other inefficiencies. For example one Powerwall might be at reserve and not offsetting load its programming tells it it wants to offset, while the other Powerwall is more highly charged and could be used to offset that load.

If your goal is just to keep the solar active during a power outage, you could move the existing solar behind the Gateway. How are the CTs currently located to measure your load, and does it measure your solar generation? [A one line diagram of all wiring would be helpful.]

Most likely the solar could be moved behind the Gateway without causing any other change in behavior. You'd just have the solar active during a power outage. Powerwall behavior during an outage does not, to my knowledge, depend on any of the CT inputs, so everything would just work during an outage, with the usual caveats.

Oh, and how did you end up with a Powerwall configured for grid charging while also having solar? Did you install the solar after the Powerwall?

Cheers, Wayne
 

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