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advice needed on budgeting for solar panels, charging

Discussion in 'Model S: Battery & Charging' started by wrysys, Sep 20, 2016.

  1. wrysys

    wrysys Member

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    #1 wrysys, Sep 20, 2016
    Last edited: Sep 20, 2016
    I'm considering a tesla s85 cpo. I have solar panels but realized I would need to almost double my panel output per month to fuel 100% of my car's commute . the estimate for my commute is 30 kwh per day using the EV trip planner. So per month consumption would be 600 kwh. I have PG&E and want to know how others have figured out their solar/rate plans:
    1) How did you budget the solar panels and do you charge every day? Or do you rely on outside chargers/superchargers?
    2) Which rate plan do you use? Seems EVA time of use is the most popular with charging late at night. We have been frugal and only run about 300-400 kwh per month consumption currently (no EV) and our current solar output covers it with a surplus at E1 pricing. I am not excited about having to order more panels and want to know how others dealt with it.
    3) Is the ev trip planner accurate? The numbers are very different from what Tesla advertises would be my charging requirements. Have others based their charging needs/solar needs based on this site?

    Thanks!
     
  2. AndreSF

    AndreSF Member

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    How large is your solar setup? And how long is your commute (based on numbers you posted, is it ~85 - 90 miles per day)?
     
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  3. Lloyd

    Lloyd Active Member

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    I would not stress about it. Get the car, see how much your car puts you over your production for a couple of months and then you can better plan on how much more solar you need. Consider going on EV rate plan.

    http://www.pge.com/tariffs/tm2/pdf/ELEC_SCHEDS_EV.pdf
     
  4. JPP

    JPP Active Member

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    I would sort of separate the 2 concepts. Yes, get on the EV-A plan. Charge your Tesla at night at the lowest rate (about $0.10/kW). See how it goes during the day as your peak rate will be high and the solar charging curve does not align with PG&Es rate plan time-of-use 'shift'. Get some data and then decide.
     
  5. brucet999

    brucet999 Active Member

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    If PG&E is like Edison, they won't allow you to increase your solar array capacity above what you are billed for in the previous 12 months. Edison does allow you to appeal after your application has been denied and then, and only then, can you submit evidence that you now have an EV that is projected to use X amount of power annually. Remember that you will consume up to 15% more from your AC electrical source than the car uses from its battery, due to line losses and in AC to DC conversion.
     
  6. No2DinosaurFuel

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    well you have the weekends and assuming you don't drive during those times, you can recoup some of the KWh then.

    Also keep in mind, you can always become more efficient for your house like turning off lights and other appliances when not needed. This helps gets you the few extra KWh.
     
  7. rxlawdude

    rxlawdude Member

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    Don't forget those pesky winter months where output is maybe 25% of summer peak output.
     
  8. davewill

    davewill Member

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    The nice thing about having an electric car is that it makes the TOU plans pretty much a no-brainer for a solar user so as long as you can defer your charging. I'm in about the same place you are, but my bill is the minimum since the bulk of my use is during the midnight to 5AM super-off-peak hours.
     
  9. JCL123

    JCL123 Member

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    Hello, I am getting my 60D in about a week.

    I have 24 300W panels, in real-world use I have seen them hit 6kW peak, and I have hit 1.2MWh in one month. My entire house is LED, and it is only 2 years old, and I have done allot to conserve. Right now I can go the whole year with no electric bill, using my credit from the summer to get through the winter, with a slight extra maybe. I have 12 months to use any credits I get.

    I own my panels rather than lease, so I could add some, but I don't have that much room left on my roof. And my inverter is 7.2kW max I think, so too many more and I would need a bigger one. Although I may need to replace it anyway if I get batteries.

    I expect the car to put me over and that I will have a small electric bill again. But, I am not unhappy about this, because I would actually rather use all of what I am generating, it is worth more to me to use it than what I get back from net metering. If it really got high and/or electric rates went up, I could see adding panels, but I am happy to wait and see.

    I am considering power wall also, but I don't have enough info on it really yet.

    I can report back as things progress.

    JCL
     
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  10. rxlawdude

    rxlawdude Member

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    @JCL, you probably don't have the awful "tiered use" plans that we see in California. The more you use, the higher the per kWh rate (till it approaches $.32/kWh in Tier 3). Even with your home at net zero consumption, if you drive 100 miles a day, you're looking at up to 950kWh per month just from the Tesla. Again, in California most of that 950kWh would be at the highest rates. Assuming you pay about $.10/kWh with no progressively costly tiers, you're looking at about $95/mo to operate your Tesla. Still FAR FAR cheaper than an ICE vehicle.

    Your system and mine are almost identical, but mine are the 275W panels with a 6kW inverter.

    California residents will have another chance to get a submeter and pay the EV rate ($.13/kWh off peak) when Phase II of the pilot program resumes in November. However, I'm now looking at changing to time of use (TOU), which has that same or slightly lower off-peak rate.

    Sorry for the California-centric rant.
     
  11. ran349

    ran349 Member

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    If you have solar panels and an electric car, the most important thing is to go on time of use (TOA), where the electric rate will be much lower when you charge your car at night.
     
  12. SageBrush

    SageBrush Active Member

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    If you do not want to put up more solar panels, I gather your question is how to finagle the lowest utility bill?

    Review your offered plans and model your consumption over a year.
     
  13. Dwdnjck

    Dwdnjck Member

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    If you are charging your car at night with a 10 cent TOU rate, you are paying less than 4 cents a mile, or $4 per 100 miles. I wouldn't lose to much sleep over it.
     
  14. JCL123

    JCL123 Member

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    No worries, I have lived in CA in the past, but I will spare you. Massachusetts has plenty of problems to worry about.

    Ouch, those tiered rates sound bad. There is talk of the regular rates getting up to about $.23/kWh, because of "natural gas lines that are too small" of all things. The difference between the day and evening / off peak rates is small, like a few pennies per kWh, but I guess every little bit helps.

    I don't use my car to commute, honestly it's mostly on the weekends. I probably drive 8,000 miles / year. So I am not expecting a huge electric bill from EV usage. I might even fit under my production, but probably that is overly hopeful.

    On the plus side, you probably have allot more sun and higher production than I do.

    I was lucky to get my 300W LG panels, the solar guy called me one day a few weeks before my install, and said "hey, wanna get these, they have like 30 left in the warehouse", so I grabbed them.

    JCL
     
  15. JCL123

    JCL123 Member

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    At least for now the difference is tiny, and you have to sign up for it. But there is talk of this changing soon.

    JCL
     
  16. PtG62901

    PtG62901 Member

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    Predictions are panels prices are going to fall next year, maybe as much as 30%.
     
  17. wrysys

    wrysys Member

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    in PGE land TOU EVA peak rates are .44 /kwh in summer, .24/kwh near peak. Those of you with someone at home needing AC, has there been a problem with the utility bills? the .44 gives me pause. Can run the dryer and other appliances at night but at 4x night time use I wonder if there is not much advantage to TOU unless one drives a certain amount. Has anyone had experience or modeled this?
     
  18. AndreSF

    AndreSF Member

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    Shouldn't your solar power generation offset this though? No A/C experience myself (no need for A/C in SFO), but I have a co-worker (lives in Dublin, CA) with Leaf, 4.7Kw solar system and wife's home biz. He is quite happy with his system and has considerable excess power generated each month.
     
  19. patrick40363

    patrick40363 Member

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    You need to generate credits during the summer to offset the tier rates you get hit with. Add as many panels as you can.
     
  20. SageBrush

    SageBrush Active Member

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    OP, your consumption and generation patterns are different than everybody else. Learn the tiers, plans, and then spend some time with a pencil and paper.
     
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