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Question about Powerwall 2 setting

Discussion in 'Tesla Energy' started by llngoc, Jul 25, 2018.

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  1. llngoc

    llngoc Member

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    I am about to have my PW2 installed tomorrow and I would like to see how to get the following setting to maximize my energy cost/use.

    Some background. I have a 5.5kW solar array (not Tesla) and is putting in a 4 PW2 unit (52kwh?). Since I have EVs, my peak power rate is from 4-9 pm. My goal is to charge only from solar since I want to take advantage of the federal tax credit and discharge during the 4-9 pm peak period only. Also, I would like to discharge to only 60% so I can have the rest of the battery as backup.

    Is this possible with the current software?

    TIA
     
  2. cwied

    cwied Member

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    Yes, this is the normal setup for an installation in the US with solar. You would set to time-based control with a backup reserve of 60%. In the US, Powerwalls installed with solar are programmed only to charge from solar to preserve eligibility for the tax credit.
     
  3. Shygar

    Shygar Member

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    Do you have enough solar to charge four powerwalls? I guess if you plan on keeping them at no less than 60% then it should be ok. I would set it to backup only for the first couple of days until your powerwalls are full, then switch it to advanced time control. Just make sure you can see the option for advanced time control after they install it because it's a setting that has to be done separately by the Tesla team behind the scenes. Otherwise you would only see backup and self powered mode, not the advanced time controls.
     
  4. llngoc

    llngoc Member

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    Good idea. I will let it stay in Backup mode for a few days.
     
  5. commasign

    commasign Tesla Superfan

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    5.5kW seems a little small for 4 Powerwalls unless you’re only using the Powerwalls for backup. Tesla’s online estimator suggests 20kW solar as a match for 4 Powerwalls. So you might have a mismatch. How many kWh do you use per day and how much does your solar PV system produce (best and worst case)?
     
  6. llngoc

    llngoc Member

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    I know I went a little overboard but my goal is for whole house backup and I would have needed 3 PWs anyway so I figured out the incremental cost of the 4th one is not too bad and went with 4 in the end.

    My plan is to charge it up during weekend offpeak hours as much as possible and do my best during the weekday with the partial peak charging.

     
  7. commasign

    commasign Tesla Superfan

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    Ah, understood. Double check to make sure they'll allow you to enable grid charging. On my setup (solar + Powerwalls), grid charging is disabled.
     
  8. llngoc

    llngoc Member

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    I am okay for solar charging even if it is slow. My array generates about 36-40kwh per day and if I dump it all into the PWs during the weekends, I should be fine. I planned to set to discharge to 50-60% and whatever saving I get from the TOU time shift, I will be happy since my main goal is the backup.

    As long as I can be sure that I am charged 100% from solar, I will be fine as I do want to take advantage of the tax credit.

     
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  9. llngoc

    llngoc Member

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    Just checked my typical summer usage and it seems like I sent around 12kwH back to PG&E during shoulder period and for the rest of the peak period, I consumed about 12kwH so I should be able to load shift for the summer. Winter will be a completely different story but I will probably use a lot less during winter's peak hour since the AC will not be running.

    Come to think of it. Two PWs probably could have been enough but well...

     

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