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Will economics of new Tesla PowerWall product will work for you?

Discussion in 'Tesla Energy' started by Zzzz..., May 1, 2015.

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  1. Zzzz...

    Zzzz... Member

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    Will economics of new Tesla PowerWall product will work for you? 10 kW/h battery pack cost $3500, inverter cost $1000 and installation $500.

    How fast such $5k system pay for itself, assuming it stores 10kW/h buying them at cheapest(night) rate and lower your consumption during peak rate by 10 kW/h.
     
  2. santana338

    santana338 Member

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    Nope. If I didn't already have a propane whole-house generator I would think about it. It would be less expensive. It would also be a gateway to adding solar. If I already had solar and no generator, I'd be all over it.
     
  3. ChadS

    ChadS Petroleum is for sissies

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    I'm sure there are plenty of places it will work. But not here. Our electric rates are the same 24 hours per day, so no advantage to taking electricity at cheap times. I have solar, but my utility does net metering so there's no advantage to using it myself or saving it for later. There's no economic incentive for me to get one.

    It's not likely to work that well for backup either, because our whole house (including heat) is electric. Most power outages are in the winter when my panels generate almost nothing, so one of these won't last very long. Several of them might, but then the cost looks prohibitive.

    I could get one as a UPS or something. No, wait, if my heat pump is working one probably won't provide enough power. I still want to see more details about how it would hook in to my solar system, if it can switch over to power everything automatically, etc.
     
  4. Joel

    Joel Active Member

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    Where did you get the $1,000 number for the inverter?
     
  5. Merrill

    Merrill Active Member

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    I do not know but if you have solar you already have an inverter, my issue is more very specific to my system and the fact that I'm on a TOU system on solar and it rewards me during peak hours, 12pm to 6pm by a credit at the high per kW charge back to my monthly bill. With the Powerwall you are storing that energy and probably not getting the advantage of that credit, so still need to study this.
     
  6. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    Won't work for me: we've already got solar panels, but our utility provides net metering so no rate shaving possibilities, and the backup capability of one Tesla Energy home unit is barely enough to cover our baseline usage for a few hours.
     
  7. djp

    djp Roadster 2.0 VIN939

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    I figure it would save a max of $200 per year given the 8.5 cent difference in peak / off-peak rates in Toronto. Not all that compelling in the city, but it would be interesting for an off-grid cabin in the woods.
     
  8. Zzzz...

    Zzzz... Member

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    For example retail prices per W for solar invertes are somewhere in between $0.33 and $0.614 PV Insights

    So for 2KW inverter we are looking at $660-$1228 range. But battery inverter might need to be bidirectional, this might cost more. But $1000 looks like reasonable optimistic assumption.
     
  9. Joel

    Joel Active Member

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    Sounds good to me. I have an 11 kW solar array. I believe in solar, and viewed it as an investment in the future, so I never paid attention to the cost of my inverters. Would the system require an inverted per Power Wall?

    What everyone Should consider is: if you expand (or add) solar to the battery purchase, it will be eligible for th 30% tax credit. So; I'm considering expanding my solar array and adding 5 to 9 batteries to take advantage of the 30% Federal Tax credit.
     
  10. eco5280

    eco5280 Member

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    This is going to sound odd, but I'm frustrated that my electricity is too cheap to make solar feasible. I pay about $0.13 / kWh and there's no on-peak off-peak nonsense. I've gotten a few quotes and doing a 10 kW system would be $30k, about a 13 year break even point. I'd definitely add the PowerWall if/when I do it, and I'm MR. GREEN and really want to do it, but argh, it's not fiscally smart for me.
     
  11. omgwtfbyobbq

    omgwtfbyobbq Member

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    If it'll last a decade at 1 cycle/day, probably. Especially if it would qualify for a 30% tax credit with a PV panel install.
     
  12. dgpcolorado

    dgpcolorado Member

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    No, not for me. I'm on a flat rate plan (13.77¢/kWh) but even with a TOU plan the difference between peak and off-peak is tiny here. I also have grid-tied solar panels (2170 watts) that provided 104% of the electricity I used to fuel my car (a LEAF) and run my house last year. So, I pay only the $16 service charge each month. My rural power co-op is also very reliable and outages are infrequent and brief, so there would be little benefit in having a battery as a backup for outages.

    These batteries seem best for those with large differences in TOU rates or for remote off-grid applications (we have a lot of off-grid solar in my rural mountain area).
     
  13. Matias

    Matias Active Member

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    #13 Matias, May 2, 2015
    Last edited: May 2, 2015
    Our peak vs off peak electricity price difference is about 5 (euro) sents. So maximum possible saving is 7kwh × 5 cents/ kwh x365 = 128 euros/year.

    So it will never pay itself with peak shaving.
     
  14. CalDreamin

    CalDreamin Member

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    I posted some estimates here for a homeowner on PG&E's EV rate plan who integrates a Powerwall into their solar PV system.
     
  15. woof

    woof Model S #P683 Blue 85 kWh

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    Doesn't work for me either. With 1:1 pricing on net metering with no TOU plan, the only gain would be as a whole house power conditioner/UPS. In that mode I'd need a lot of battery, and a complete redesign of the existing panels to allow for emergency power and prevent grid back feed. That, combined with the fact the Solar panels/inverters are SolarCity's and not mine, means no Powerwall for me.
     
  16. wk057

    wk057 Senior Tinkerer

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    You've fallen into the trap. The 10kWh version is not for daily cycling.

    Elon, I love you... but the PowerWall isn't that great...... yet.
     
  17. Papafox

    Papafox Active Member

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    #17 Papafox, May 2, 2015
    Last edited: May 2, 2015
    OK, here's my plan...
    One 7kwh pack plus inverter plus install = approx $5000 financed over six years with 3% after tax interest (using my home equity LOC) = $76/mo. cash cost/mo.
    Shifting 7kwh of energy from prime to best rate at 11.5 cents/kwh savings= 0.81/day savings x 30 days = $24.30/mo savings, thus neg cashflow of $76-$24.30 = $51.70/mo neg cash flow for years 1-6 and then positive cashflow from system for remaining life of battery. Break even point after those first six years would be an additional 12 years if battery lasted that long...
    BUT
    For less than $52/mo. I have found a way to use my substantial bank of PV panels as backup power during times of grid power outage. I will be working from home on my computer, and so the reliability and the ability to work in times of power failures will easily compensate me for that $52/mo. charge. I see the Tesla powerwall as more of a buffer that allows me to take advantage of my substantial PV output when the grid is down. In other words, I'm running my home with a fair amount of electricity when the sun is out and the PVs can produce more than is needed. The 7kwh battery is used to enable the daytime flow of electricity from PV panels to home uses during the daytime and to carry me through the night. Most likely I would add another 7kwh battery to the mix.

    Hawaii has the country's highest percentage of homes producing power from PVs, but nearly all of these homes have no ability to continue normal electrical operations when the grid is down. The Tesla home battery allows off grid normal operations of my home during daylight hours, which is worth quite a bit more to me than the tiny monthly cost. I might even go for the 10kwh battery and not worry about load shifting, the ability to maintain my household electricity functioning when the grid is down is the most important reason for getting one or two of these batteries.

    Today two of my neighbors were talking about adding the Tesla home battery so that they too could take advantage of their PVs while the grid is down. In the words of Elon Musk, batteries are "the missing piece". The utility provided to existing PV owners for the cost is very attractive. My name is on the list for early install. Can't wait.
     
  18. Robert.Boston

    Robert.Boston Model S VIN P01536

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  19. CalDreamin

    CalDreamin Member

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    I'm guessing that the 7 kWh and 10 kWh Powerwalls have the same battery, but the DoD is limited on the 7 kWh version to extend battery life.
     
  20. MSEV

    MSEV Member

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    Doesn't work for me (Omaha, Nebraska, USA). 5kW PVs, low cost electricity (about 11 cents), net metering (wholesale, about 4 cents to me) but I don't often produce enough (monthly basis). If I add 6 more kW PVs, up to my max roof space, then it might be worth it because I might have a number of months with excess power. Also there is the problem of the utilites don't allow me to use PVs during power interuption, but they interuptions are infrequent and very short usually.
     

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