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batteries vs generator

Discussion in 'Tesla Energy' started by h2ofun, Oct 30, 2020.

  1. jjrandorin

    jjrandorin Moderator, Model 3, Tesla Energy Forums

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    The missing parts that it appears you dont want to look at are:

    1. Everyone is different. Generators are a non starter for some. Personally, I would have never considered a generator, no matter the cost difference.
    2. Generator + Propane or Generator + gas is, by definition, a net negative. There is no scenario where that helps reduce costs even a little bit. Every dollar spent on that solution is just dollars spent on a backup solution.
    3. Battery storage to go with solar may or may not pay for itself (and if it does, the ROI is pretty long) but it can, in the right circumstances, reduce costs, so is NOT a net negative from a cost perspective like a generator is. Those "right circumstances" are a big delta between off peak and peak usage, like most in california have.
    4. No one beside you in this thread is talking about "100k install costs" for solar + powerwalls. Of course everyones install situation is different, but "most" are not going to have 400 amp service where they have to, because of infrastructure considerations, buy two different systems.
    5. Saying " no one needs to run everything during a poweroutage" may be right for you, and thats fine, but just because something is right for you, doesnt mean its right for everyone. I could easily say something like " No one needs 400 amp service in their home, who needs all that power?", which would be a somewhat ignorant statement, because even though "I" dont need that much power, its obvious some do.

    Summarizing / TL ; DR

    Everyones situation is different, and what works for one person doesnt have to work for everyone. Some have an issue with generators on principle and would never get one for one reason or another. Generators always cost money and do nothing to defray anything they cost to install, while battery storage can defray a little, some, or a lot of the install costs depending on a persons Utility costs. Neither likely "pays for itself" but 100% of a generator cost and usage is sunk cost for backup purposes, while some of a powerwalls costs can be recouped in the right circumstances.
     
    • Like x 6
  2. Dukeybootie

    Dukeybootie Member

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    I get ~45-50 kwh per day in the summer with my 20 panel system. Currently averaging 27 kwh daily. The 2 Powerwalls get fully recharged by 10am in the winter and 2pm in the summer (Powerwalls drained more in summer due to A/C use). So, no concerns with inability to recharge unless there are numerous consecutive hot cloudy summer days. I am actually looking into getting more panels and another Powerwall while the federal tax credit still exists. The wife just shakes her head but she gets her home improvement budget and I get mine, so that's that.
     
    • Like x 1
  3. getakey

    getakey Member

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    I am on PG&E TOU plan. I still have 2pm to 9pm Peak.


    I had solar before the batteries. My annual true up before batteries was between $50 and $100. However, I added a heat pump to replace dying AC/furnace after that true up. That is for 1/2 my house. Still have AC/furnace for the other 1/2 of house.

    In summer, the delta Peak to Off Peak rate for me is 25 cents. I think it maybe more this year. I can easily pull about 28kWh from the PWs during the summer. Thats about $7/day for about a solid 4 months. On hot days (>95), I hit my reserve before Peak ends, so I could pull more by lowering my reserve if I wanted to.

    In winter, delta is 17 cents. I don’t have data yet with the heat pump, but my estimate is at least 10kWh can be pulled from PWs during peak. I’ll also estimate 3 months of that which is $3./day

    Spring/summer is at least 6kWh from PW during Peak. I’ll use 17 cents to be conservative, but the summer to winter rate cross over is sometime during this time period. So I have ~$1/day for 5 months.

    Doing all the math, I'll save $1,146 per year. My net cost for 3 PWs was $16,560. Result is 14.5 year payback.


    However, in my situation, I made the decision to get a full backup after the PSPS events last year. I was either going to get a generator or PWs. I was not going to do nothing. Thus, I compared price of generator to PWs. I got one quote for generator that was actually more than the PWs. But, for this analysis, I’ll use the lower generator quote which was $6K less than PWs. Therefore my payback with PWs compared to generator is actually 6 years.


    The only thing that may make my benefit less is if the PW puts me in a negative True-up. Since I do not have data for winter with heat pump yet, I don’t know what the true up situation will be.


    Its like deciding which car to buy. I need a car. Like comparing ICE to EV. EV costs more, but since maintenance and per mile costs are less, I decide to buy EV which has lower cost of ownership after 5 years.


    There is no ROI with a generator.
     
    • Like x 2
  4. getakey

    getakey Member

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    see my post above
     
  5. h2ofun

    h2ofun Active Member

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    I understand all that and agree.

    I continue to wait for the data that supports folks telling me in a normal grid use, that batteries have a decent ROI. This is not out outages, or generator. It is folks saying in normal operation, they is a decent ROI. My data, as I posted, show with my solar, I will have a negative PGE bill. So, for me, and I would guess many others, for normal operation, solar is all one needs.

    Now, for power outages, yep, this is totally personal, IMO. But, to say batteries, which are only needed for a power outage, or even a generator has a decent ROI is, well, .. My generator was a life style decision my wife wanted to be able to flush our toilets since we have a pump. Did I totally over kill it with NO ROI. Yep, WIth the construction I had going on, it was a once in a life time opportunity. Now, I am trying to get the free batteries, since yep, they would be more quiet. But if I have
    Now, that is a fair ROI.

    For a power outage, ROI does not matter. But if I have a long one in the dead of winter like I have had before, with one being 4 days, no way would batteries be charged enough from the solar charging to run my mini split heat pumps.SO generator for me is best.

    So, I got the generator because of how my remodel was happening. Would not have made sense to do later. So since I have negative PGE with just my solar panels for the year, batteries would have an infinite payback for me. But if I can get for free, I love technology.
     
  6. getakey

    getakey Member

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    what is you consumption during winter? Pretty sure I can make at least 4 days in the Winter and I have a heat pump for half of the house
     
  7. jjrandorin

    jjrandorin Moderator, Model 3, Tesla Energy Forums

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    If @h2ofun has 400 amp service, and is telling us that he would have to install 2 separate systems because he could not put all his home loads on one 200 amp panel, then its likely that to meet his consumption numbers he would need a number of powerwalls that is fairly obsessive to even contemplate that.

    This is a situation where, for him, in his situation, I dont think it makes sense. In fact, I dont even think the free ones make sense, because what exactly is he backing up with 1 or even 2 free powerwalls, based on his consumption and stated home loads.
     
  8. h2ofun

    h2ofun Active Member

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    No idea yet. I just had installed 9 heats. But if I turned them all on, I would guess 10K per hour. So, this would drain batteries real fast if I wanted them all one. I have not turned on really yet but we have a 25 degree temp drop from thurs to friday so my time is coming. I am just lucky that from a day to day use, I have it looks like way more solar than I can use. If this turns out to be turn, I will be running the ac and heat a lot more. :) But until I get a year of data. I do love having the mini split heads since I am now 100% zoned and only have to run a very few worse cash for a while. Luckily wife likes house cold, but not hot.

    I did a load test and pulled like 41kwh for my entire house running.. That would hurt it steady state.
     
  9. getakey

    getakey Member

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    you have 9 mini-splits?
    full load is 41 kW, but not for an entire hour. Will be interested to see what you actual consumption is when it gets cold
     
  10. h2ofun

    h2ofun Active Member

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    I have a 5 thousand sq foot home. Yep, 9 mini splits.

    For my full load green button data for pge, I have an hour at 35.03 kwh. The 41 was worse case I saw on meter. Again, I lit up the house to see what it would do, but that is what I pulled.

    I would never use that much, I hope. I also hope to only turn a few heads on . Just depends who is living in the house. I am ready for any need since we have a number of older family members that may need to move in with us, especially during a power outage.
     
  11. getakey

    getakey Member

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    what does each mini consume? These are heat pumps - right?
    That seems crazy high
     
  12. h2ofun

    h2ofun Active Member

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    Again, this was everything in my house. I will be finding out shortly what just the mini splits use
     
  13. Zorg

    Zorg Active Member

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    I am fairly confident that my powerwalls won't pay for themselves, but I like the insurance they provide. And they're clean, quiet and don't take much space.

    OP keeps mentioning free PW. I thought that SGIP was done in CA. Not quite following.
     
  14. h2ofun

    h2ofun Active Member

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    Nope, tons of money left for the next few years in SGIP calif. Just gets released in phases. Mine is still in review. Hope to hear answer any day. The question I hope is just what quantity I can get for free.
     
  15. Zorg

    Zorg Active Member

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    What level of rebate are you expecting from SGIP?
     
  16. h2ofun

    h2ofun Active Member

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    Hoping for 100% free at 1000 per kwh
     
  17. jjrandorin

    jjrandorin Moderator, Model 3, Tesla Energy Forums

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    There are multiple SGIP programs, and but the only one that can provide rebates for a "free" powerwall or two are the equity and resiliency program. That program has specific restrictions you can google and look up, but obviously @h2ofun has already done that and believes he qualifies for it.
     
  18. h2ofun

    h2ofun Active Member

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    I know a number of folks who have qualified under those programs and have full approvals for free batteries. They are just now waiting to get them allocated from Tesla to their installer to be installed.
     
  19. jjrandorin

    jjrandorin Moderator, Model 3, Tesla Energy Forums

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    You just need to be very clear when posting here about SGIP and saying "there is plenty of money" because that program does not apply to "most" people in california. It does apply to quite a few, but its not "most", while the "regular" SGIP program applies to everyone in california if there is money for it (which in general is gone the second they release it) for less than 3 powerwalls, and also is down to 2k ish each or so).
     
    • Like x 1
  20. Zorg

    Zorg Active Member

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    Got it. Then, if the powerwalls are free, I really don't get the goal of this thread. It's a no brainer.
     

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