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Tesla PowerWall thoughts...

Discussion in 'Australia & New Zealand' started by GregHudson, Oct 28, 2015.

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  1. GregHudson

    GregHudson Member

    Joined:
    Apr 2, 2015
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    Location:
    Australia
    This is a subject dear to my heart, even though I haven't got my Tesla yet...
    I only have a 2Kw solar array (biggest I could fit on the roof) all North facing, with no shadowing, located in Melbourne. (Av 5 hours sun/day)
    I also managed to get the PFIT (Premium Feed In Tariff) on the very last day it was available, which locks me in to a healthy minimum of 66c/Kwh for exports up to the year 2025.
    Unfortunately, we are moving soon, and it will transfer to the new owner :-(
    If I was staying, I have been thinking about how to balance the power generated, exported, used during peak, and used during off peak.
    Average usage is around 500 to 750w per hour (24/7) - I have heaps of computers & stuff running...
    Battery storage would be the logical choice (i.e. Tesla PowerWall, or even better, the Tesla itself) but, with or without, it becomes a careful balancing act.
    Basically, I need a battery to charge up after 11pm, then supply power from 7am (peak start) until the sun can generate enough to start exporting, at which time the battery should be disconnected so I'm not putting my valuable 66c exports into the battery. Late afternoon (when the solar output drops), the battery then needs to power the house until 11pm when off-peak rate cuts in, then start filling the battery once more, starting the whole process over again. This would be the preferred option... Has anyone else made similar considerations ?
     
  2. ZTrekus

    ZTrekus Member

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    Location:
    Sydney, NSW
    Not sure of all the legal niceties, but I think you might invalidate your feed-in tariff once you have a battery installed (ie, the conditions might require you to be only solar no battery).

    Otherwise an unscrupulous person could feed the battery up at night and discharge it at the feed-in tariff rate - making someone or other go completely psycho as you make a killing!

    ---

    You can of course feed the battery at off-peak and discharge it during peak hours - which is what it is designed to do. But feed-in tariffs are a deal breaker I would think.
     
  3. moemoke

    moemoke Member

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    Oct 10, 2014
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    Location:
    Moe, Victoria, Australia
    I've been thinking about this recently as we have much the same system as you with the PFIT and would love to go semi off grid so rather than replace our
    existing inverter etc I was wondering how we could setup some more panels than feed straight into battery storage to run the house and the existing system
    just feeding into the grid at 66c/kwh, if the battery did discharge to much by bad weather etc I could flick a switch which would but us back onto the grid.
    We use around 7kwh/day in summer and about 11kwh/day in winter so I'd think 2 or 3 Tesla powerwalls would be all that's needed plus the new panels and inverter etc.
     
  4. paulp

    paulp Member

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    Location:
    Adelaide, Australia
    If you are being paid 66c to generate power, battery storage makes no financial sense. Use the grid as your battery as it will leave you financially better than powerwall.
     
  5. Dborn

    Dborn Confirmed

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    Aug 26, 2011
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    Location:
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    But what if you are half and half? 3 kW on NSW 60 c fit and 3 on 7c. Mind you, we lose the 60c next year, but not sure when. Will probably go the battery route then.
     
  6. paulp

    paulp Member

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    Location:
    Adelaide, Australia
    The battery solution starts to make sense at 7c, but its still financially questionable due to the relatively short life. They are likely to do a full cycle every day.
     

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