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Charge PW at night when it's cheap and use stored energy during the day?

Discussion in 'Tesla Energy' started by RyanDe, Jun 15, 2018.

  1. RyanDe

    RyanDe Member

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    Is this possible? Our local utility offers $0.024 power after 7pm until 12am but $0.096 during peak. Trying to figure out if we use a PW to only pay the $0.024 or not.
     
  2. zanary

    zanary Member

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    Yes. That feature is called Time of Use Load Shifting or what Tesla calls Time-Based Controi. In my case, I use two Powerwall to purchase electricity from PG&E from 11pm and 7am at $0.13/kw and use it when the price is $0.47/kw. Works perfectly for me.

    you'll need to work with Tesla to determine how many Powerwall you need at your house depending on your panel. In my case, I have a kitchen range on a 50 amp breaker, so I need two Powerwalls, because each Powerwall can only support 30amp. I do have a 3rd one coming, so that way I can allocate two of them for Time-Based Control, and keep the third one's capacity reserved for a power failure.
     
    • Helpful x 1
  3. cwied

    cwied Member

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    #3 cwied, Jun 15, 2018
    Last edited: Jun 15, 2018
    One caveat that might not be obvious: if you have solar, you can't do this. Powerwalls installed alongside a solar system will (currently) only charge from solar so that they meet the requirements of the federal tax credit.
     
    • Disagree x 1
  4. MP3Mike

    MP3Mike Well-Known Member

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    Do they actually let you do that, or would you have to have a second system/energy gateway to support that?
     
  5. cwied

    cwied Member

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    Not literally, but if you set your backup reserve to 33% it would have the same effect.
     
  6. RyanDe

    RyanDe Member

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    I’d probably need two then, that makes the payback really long. I wish my house was located for solar as that seems like the batter alternative.
     
  7. Electroman

    Electroman Active Member

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    Mine is even better. $0.14 during day and $0 at night. Yes free at night.

    I called our utility to find out if it’s okay to charge batteries at night and then use that durIng day. They don’t seem to have any problem with that. My consumption during day is around $1500 kWh per month during peak summer months and so I am guessing I need quite a few PW. And also perhaps as additional panels and an extra phase ? My panels are maxed out now.

    The problem is though there is 6+month waiting period for PW.
     
  8. NuShrike

    NuShrike Member

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    You can ask your installer to install the battery as "standalone" instead of "paired" storage. Then, you can freely charge from the grid as you're not taking the federal-credit rebate.

    Wayne (wwhitney), in the forum, is doing that. His problem is now how to get TBC working when you DO have on-site solar, but the PW isn't officially installed/paired with solar support ...

    I've also asked my installer to do this, with approval confirmation from SGIP, and independent approval confirmation from SGIP via my my installer.
     
    • Informative x 1
  9. cwied

    cwied Member

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    Ah, interesting. I saw that he was asking them to do that, but I didn't know they had actually done it. As I understand it, TBC without solar should be similar to TBC with solar except it doesn't have the two modes: https://www.tesla.com/support/energy/own/powerwall/modes-of-operationwithpowerwallwithoutsolar

    The other interesting question is if the "standalone" Powerwalls can be convinced to charge from solar when the grid is down.
     
  10. wwhitney

    wwhitney Member

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    I'm looking into having the Powerwalls configured as standalone, even though I have solar, but I haven't actually asked Tesla about it yet. NuShrike, what did Tesla tell you, and when is your install? [Sorry if you've mentioned already in another thread.]

    Cheers, Wayne
     
    • Informative x 1
    • Like x 1
  11. NuShrike

    NuShrike Member

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    Hey Wayne, I'm installing via third-party installer as it was a tiny-premium to go with them vs doing the SGIP dev myself. I'm was supposed to install by June, but looks like Tesla's battery inventory is still depleted.

    I did ask my installer whom confirmed with SGIP: as long as the final ICF says standalone, that's the only document that matters in defining what's installed.

    As for TBC issues, I think at worse I'll just stay with self-consumption, with a calculated reserve (after doing a few annual simulations via SAM). That should allow night-time charging, and proper daytime discharge.

    At best, play with the APIs to programmatically do what TBC isn't doing. IFTTT would've been nice here.
     
  12. CA-Gbm84

    CA-Gbm84 Member

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    There is no such thing as self-consumption with a stand-alone Powerwall
    - Powerwall will have solar meters disabled, so there is no 'visibility' to charge or discharge in relation to production
    - You will only charge from the grid at a set rate and discharge to home load based on peak times
     
    • Informative x 1
  13. dutchinchicago

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    This federal tax credit only applies when you install the batteries at the same time as solar panels right?

    If that is the case I really hope that they allow a mixed mode. I want to top up the batteries at night using cheap power and during the day store any tempory excess solar capacity from my existing solar installation and self-consume up till a base reserve to cover power outages.

    This is what I had always assumed they would be doing. Do you think this will be possible at some point?
     
  14. cwied

    cwied Member

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    No, you can claim the ITC even if you install the batteries with a pre-existing solar system. I suspect that's why the modes with solar are implemented the way they are.
     

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