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Sell me on the Powerwall

Discussion in 'Energy, Environment, and Policy' started by Racerx22b, Jun 12, 2017.

  1. Racerx22b

    Racerx22b Member

    Joined:
    Nov 17, 2014
    Messages:
    550
    Location:
    West Palm Beach, FL
    My utility company (Florida Power and Light) does not technically buy back electric (at least not at retail pricing) but they do credit me 11months of the year for any overage.

    I have an 11.69kw solar array and my bill goes from $20-$100/month. Any extra power made from Jan-Nov gets traded back and forth evenly as credit on my bill (no actual money is provided to me). So if I made 20kWh extra this month and used 20kWh the following month I would essentially own nothing. It gets balanced out each month and then at the end of December anything extra I have leftover (which I wouldn't have) would be bought back from me at wholesale pricing. They would send me a check. I think it's like 3 cents a kW.

    Since any extra power I use goes into a credit status from month to month would having a power wall actually save me any money? The only advantage I can see is having battery backup. It would seem logical that any solar power we generate that charges the battery in the power wall would take away from the power we send back to the grid. This would essentially be a wash. If it took 10kWh to charge the batter back up that would be 10kWh less power going back to FPL. Right?

    I think I would need to buy at least 2 Powerwalls to run my house as well so it would be pricey. We have 200amp service and our panel is maxed out. We only have one 50amp circuit to charge both our Teslas.

    I am sure I used some wrong terminology in this posting but I think I gave enough for you to understand the heart of my question.
     
  2. malcolm

    malcolm Active Member

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    It hinges on the wholesale rate that you get paid vs the domestic rate you are charged. Yes 20kWh balances 20kWh, but the money will be different.

    Does that difference make it cost effective to time shift electricity from the day into evening domestic use or from the day into overnight vehicle charging?
     
  3. miimura

    miimura Active Member

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    Location:
    Los Altos, CA
    It also depends on whether you have Time of Use metering. My solar earns me differing amounts of credit ($/kWh) depending on when it goes into the grid. You should look at the threads in the Tesla Motors - Tesla Energy sub-forum for more information about the PowerWall.
     
  4. TheTalkingMule

    TheTalkingMule Active Member

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    Location:
    Philadelphia, PA
    It sounds to me like you have normal net metering that is "squared" once a year and you're paid wholesale on that extra overage(that you likely never have). If that's the case then there's no much need for a Powerwall as of yet, the grid is acting as your battery(and helping your neighbors).

    Net metering will go away eventually, but until it does you're fine. 10 years from now, everyone is FL will just sell their electricity on an open market. "Solar electricity" will be cheap since there will be far far far more of it than peak demand requires. When that happens you'll want a cheap battery to hold onto that supply and use it at night.

    * I'm not an expert
     
    • Informative x 2
  5. Racerx22b

    Racerx22b Member

    Joined:
    Nov 17, 2014
    Messages:
    550
    Location:
    West Palm Beach, FL
    This is basically how I understood it but I am not an expert so I figured I would ask. 2 non experts with same outlook to me confirms we are on the right path. Thanks for your input.
     
    • Like x 1

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