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Powerwall and off peak electric

Discussion in 'Tesla Energy' started by Periokid, Mar 31, 2017.

  1. Periokid

    Periokid Member

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    Is this a feasible scenario?

    Get a Powerwall, change my electric service to time of use, run off battery during the day and charge powerwall and tesla at night.

    Financially, I wonder if this makes any sense.

    Electric rates where I live are very high.

    I currently have rate 180. Thinking of 188. See photos.
     

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  2. Ampster

    Ampster Member

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    Run the numbers. You have a $0.46 differential in summer but only a $0.16 rate differential in the winter. I didn't do a Powerwall but found a 15kWhr battery with a separate inverter and put it together for $6000. It still had a 15 year payback and my rate differentials are $035 in summer and $0.25 in the winter. I found I could only shiift 6kWhr a day and my losses were a lot more than with a PoweWall. It is a hobby for me and the extra benefit is I have battery backup.
     
  3. doubleohwhat

    doubleohwhat Supporting Member

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    What battery and inverter did you go with?
     
  4. Ampster

    Ampster Member

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    I have a 4kW Outback Radian inverter with a Mate3 interface that gives me a cloud based way to change my load shifting. Initially I used a Lithium ion pack from a VW that I had converted to electric (a cumbersome V2H). I am now using a salvaged Nissan Leaf pack that I reconfigured to run at 60 volts.
     
  5. montreid

    montreid Member

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    Yeah, a standalone system designed solely for arbitrage is not economically feasible with the extended ROI, even under ideal circumstances --netmetering, hi TOU differential, shifting relatively large amounts of energy (15kw is a decent clip even over 5 hours--especially on a Leaf battery!),

    That is why investing in separate components really doesn't make sense. If you have a PV array already and paid for inverter for that purpose, then the costs are dramatically lower. Extend that further, and if you have an EV that's parked at home in the evenings after work (or a 2nd EV sitting at home during peak generation hours) - viola. Virtual powerwall with your EV.

    Of course Tesla doesn't like that since it doesn't sell Powerwalls. That's why solaredge hasn't (the inverter that's packaged with powerwalls) hasn't opened up their inverters for this nor Tesla or any other invested energy/battery company (Nissan and BMW) opened up their cars to do this . It'll have to come from a nonEnergy car company like Honda/GM/Kia to push this or 3rd party solution -- Ampster looking at you! :)
     
  6. Ampster

    Ampster Member

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    That is not what I told my wife and I'm sticking to that story. LOL Of course "economically feasible" depends on one's own internal cost of funds. Mine is low and for a hobby to have a 15 year payback I am happy. Besides it gave me a free backup. Or I paid $1000 for a 8 hour backup and have a 12 year return on investment. In addition I am somewhat immune to shifts in the TOU rate periods and in California that may have some risk mitigation payback. No, not for everyone but neither is a Tesla.
     
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  7. montreid

    montreid Member

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    Took a look at the radian; nice to see tech has evolved from the old battery backup days; the radian is able to be programmed to sense loads and grid tied to draw at specific levels...so I presume that means you can program to fully discharge at whatever peak and fully charge at super off peak hours to completely full advantage of arbitrage.

    Definitely agree on the TOU shifts coming in 2019. Luckily we're grandfathered into old netmetering schedules for at least until 2022.

    I totally agree on the point is also to have backup generation (and justify another $1000 savings from that ROI.) The final step is to hack the programming of the EVs to allow for the plug in and play nicely with our PV Solar. Just waiting for a time to leverage all that stored energy.
     
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  8. Ampster

    Ampster Member

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    I don't fully discharge because I want to have a reserve in case there is a blackout. I set the grid use timer to drop the grid in the afternoons and get me to 8pm when I roll off peak rates. I use a separate timer to turn on a separate charger controlled by the BMS.
     
  9. doubleohwhat

    doubleohwhat Supporting Member

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    I'm investigating using a Radian with a salvaged pack instead of getting powerwalls. Do you have an info you can point me to? I'm looking at the Radian GS4048A.
     
  10. Ampster

    Ampster Member

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  11. doubleohwhat

    doubleohwhat Supporting Member

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    Much appreciated.
     

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