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Tesla Powerwall 2 installation (does it make sense?)

Discussion in 'Tesla Energy' started by gtrplyr1, Aug 30, 2017.

  1. gtrplyr1

    gtrplyr1 Member

    Joined:
    Aug 30, 2017
    Messages:
    7
    Location:
    Burbank CA
    Hi all,

    Tesla shareholder ..... love the company and it's products.

    I'm currently waiting patiently for my Model 3 reservation ... meanwhile we just built a new house and I'm in the process of installing solar. Even though I had a few companies come out to bid my intention was and is to go with Tesla Energy .... so we are in the middle of the process right now , with any luck it will be installed and up within 4 weeks.

    I live in Southern CA and the installation of the solar panels is a no brainer ... I'll basically be paying the same amount to my financing company that would normally go to my electric company and after 10 years I'll own the system. What is a bit of a struggle to justify right now is the addition of Powerwalls. My local utility company will simply "bank" my excess energy and then apply it straight to any usage from the grid so it's not like they will be paying me a fraction of what they sell energy to me for. I find it hard to believe that this won't change sometime in the future as more people adopt this technology but for now they are acting like a gigantic power wall. This power company does not change pricing for peak hours ... instead they have a tiered system so once again there seems to be little benefit in having a power wall that can provide energy during "peak times" as we don't really have them .... once again ... yet.

    So the only advantage is during blackouts .... I've lived in this city 20 years and can not remember when we had a "blackout" .... it's incredibly stable around here. Now ... I live in earthquake country and if we were to suffer a bad quake assuming the house wasn't damaged and they happen to shut off power for an extended period I would be good but that is a lot of "ifs".

    I'm a sucker for tech and the idea of those power walls seems really cool ... and there is a pretty good rebate in the state of CA right now which will not last .... but what am I missing ? Does adding the power walls make any sense ?

    As much as I love tech .... in 5 years when the electric company changes it's pricing methods I would imagine we would have a significantly improved battery available .... probably cheaper and way more efficient than what would be in my house.

    Would love to get the opinion of any of you who have installed these or thought about installing them.

    Regards,

    Gtrplyr1
     
  2. Tam

    Tam Active Member

    Joined:
    Nov 25, 2012
    Messages:
    2,869
    Location:
    Visalia, CA
    In profitability terms, if you can do Time-of-Use arbitrage then it makes sense: charge free from your solar and sells during the peak time if possible. Or you can charge during the cheapest time and sell during the peak time.

    If not, just use the grid as if it's your "battery".

    Beyond that there's a public environmental profit: you have an option to help the grid out when it's stressed and need extra boost. It's profitable for utilities and neighbors but not particularly for you (I think that's the same way as some people spend time, energy and money to save the dolphins...)
     
  3. SoundDaTrumpet

    Joined:
    Jun 22, 2017
    Messages:
    73
    Location:
    Bay Area, California
    There are other threads addressing your question from this past week.

    Help requested: To Powerwall not to powerwall w/ solar PV

    The next one is exhaustive, "Powerwall waiting list" but covers many topics and probably should be split and reorganized (electrical stuff, actual installations, third party installers, fed tax credits, state incentives from California, demand response platforms, and lately performance data monitoring / user interfaces). Grant it this particular thread are buyers who already made up their mind. Hence reason for your post. The granddaddy of all threads:

    Powerwall 2 "waiting list"

    I hope this helps.
     
  4. bkp_duke

    bkp_duke Member

    Joined:
    May 15, 2016
    Messages:
    874
    Location:
    San Diego, CA
    The TOU shifting is just theoretical at this time. Per someone in the main PW thread, this is not currently something you can force the system to do.


    Regarding the OP's original questions - I'm SoCal and have solar, and have two PWs on order. I've gone through the same back and forth as you and the ONLY way it makes any financial sense is if I get in on the SGIP rebate to cut the installed cost of the systems down. Otherwise, the PWs will never pay for themselves, not before the batteries in them die.
     
  5. SoundDaTrumpet

    Joined:
    Jun 22, 2017
    Messages:
    73
    Location:
    Bay Area, California
    It sounds like there are some limitations to what the Tesla software can do for TOU shifting. On a personal note, I examined my excess solar production from smart meter data, and figured out I could shift that power into evening usage. Based upon 12 months historical data, I can rate arbitrage only about ~$200 of credits annually. This assumes hand-on tweaking of the Tesla app % of battery reserve setting each month to maximize rate arbitrage using renewable energy (in self powered mode). The downside with my approach is that if I am not home for he day, I can potentially charge my car with solar which I don't want because that's like unhelpful rate arbitrage. That would be too much wear and tear on the battery to charge my EV for zero monetary benefit.

    There is a lot of variables that figure into whether or not PW will pay for themselves. Need to have Fed Tax ITC and CA SGIP (Step 2 or better) in play. Installation costs need to be at the absolute lowest: (a) no panel upgrades, (b) no concrete work, (c) no hidden conduit, and (d) shopped for the lowest bidder. If demand response programs get integrated with the Tesla app, that'll be icing on the cake.
     
    • Like x 1
  6. miimura

    miimura Active Member

    Joined:
    Aug 21, 2013
    Messages:
    2,115
    Location:
    Los Altos, CA
    I have thought about how to make an accurate estimation of my arbitrage potential based on the existing Self Powered Mode in the PowerWall. However, in order to do it with any accuracy, I have to extract my solar production from Enphase Enlighten during only the Peak rate period. I haven't figured out how to do that. Then I can add that to my SmartMeter data to know my household usage during that period. The kWh consumed during those hours during the whole year would be the limit of my arbitrage. My previous estimate was based on the ability for force discharge a fixed number of kWh every day during Peak hours.

    I also want the ability to disallow PowerWall discharge during Off-Peak hours 11pm-7am if the grid is healthy. I don't want the negative arbitrage and efficiency loss of charging my cars from the PowerWall(s) when grid electricity is cheap. My solar is small, so I don't have any to spare.
     
  7. SoundDaTrumpet

    Joined:
    Jun 22, 2017
    Messages:
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    Location:
    Bay Area, California
    Have you tried subtracting solar production modeled from NREL's PVWatts Calculator from your Smartmeter data? Predicted solar minus actual grid consumption should be close enough for you.

    I estimated my rate arbitrage taking excess when Smart Data went negative from 7AM-2PM (ignoring the daylight savings discrepancies in spring and fall) applied everyday (more conservative calculation) and summed it up for 6 months then multiplied by the rate delta ~20cents. Repeated it for winter 6 months at ~12 cents delta. That amount would be best case scenario. Most rate arbitrage comes from the summer due to rates and more sun. With the app, 50% reserve would be optimal to obtain the goal of discharging until 9PM, and using 9PM-11PM as a soft crossover point to go back on grid power.
     

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