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Thinking to Add more Solar to Offset Charging but...

Discussion in 'Model 3: Battery & Charging' started by Glamisduner, Jul 14, 2018.

  1. Glamisduner

    Glamisduner Member

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    #1 Glamisduner, Jul 14, 2018
    Last edited: Jul 14, 2018
    Its expensive. I could use some help on my estimates.
    I have a 1400 sqft house.
    Currently I have a 7kw solar system built in 2014 and my power bill last year was $1040 for the whole year current usage estimate of around 4000kw + my solar loan of $250 a month ($4040). I am NEM1 California so I am grandfathered in for another 16 years to stick with the tiered plan which means whatever power I produce I either use or get a 1:1 credit for. Tier 1 is $.27 per kw Tier2 is $.47 summer
    $.23 / .40 winter.
    Baseline limit is pretty low but the idea is that I want to stay in tier 1.

    This year I added a chevy volt at the end of march. It gets me roughly 40 miles a day on electric off it's 10kw battery (it's actually 16.5 kWh lithium-ion but I believe only 10.4 or so is usable?). My Commute is 82 miles.

    Efficiencies aside I would need twice that much power to get to work and back in all electric. So I am estimating 25kw of power a day for my commute. Or using tesla math 70kw/310 = x/82 = 18.5 kw to commute to work and back assuming I'm not using heater or AC driving 50 or what have you. I think 25kw is a better number to use.

    So thats 261 days a year. = 6525kw for cummuting.
    +
    104 Weekends and I will assume I drive 1/2 as much (I probably really drive more but whatever).
    so 13kw*104 = 1352kw

    Total estimated usage is (7877kw) per year. Round this up to 8000kw.

    Solar company is suggesting I add 4.6kw system which for me should produce around 5,756kw (seems lower than I need so I will follow up with them).

    Current electric bill cost is estimated to be $80 a month and cost after adding the system will be $11 but cost of adding the system will be $93

    $93-11 = $82 for the loan, which includes my tax credit paid into the loan. :( So it's more expensive to add more solar than to just pay my electric bill. However once I add in the model 3, that will be another 8000kw per year in power, most of which will be at a tier 2 rate. Or the cost of $.40 (using winter rate since some will still be in tier 1) = $3200 per year say $3000 for estimation purposes + the $1040 I already pay so $4040 a year for power for the tesla (yes this is more than gas).

    Where as if I add the system it will compensate for the car. So my cost would be around the same as now maybe $1200 per year for power (it will go up a bit) and $1116 for the loan. or $2316.

    I'd save around $1700 - $1800 per year if I add solar?

    Now there's TONS of estimation and rounding here but the whole situation is VERY hard to be accurate about. WAY too many variables.


    This is assuming I put more panels up without permits to stay in NEM1. If I go to NEM2 and have to pay TOU, my system would be undersized and I would end up paying more money.

    I don't even know how to calculate switching to TOU as it just introduces a gazillion more variables.
     
  2. Glamisduner

    Glamisduner Member

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    cant edit so TLDR:
    Cost of power per year is currently $4040.
    Estimated cost of charging the telsa is $3000.
    New Total power cost is around $7000

    Cost of power per year with adding solar and a 20 year solar loan adds around $1200-$1400
    Solar loan saves me about $1500 a year for power, but I have a 15 year loan :(.
    New total cost of power is around $5500 a year.
     
  3. TT97

    TT97 Member

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    Have you checked the TOU rates? As you are producing (selling) power during peak hours and you would be using the most power during off peak to charge the vehicles, in many places the TOU rate would be cheaper.
     
  4. Glamisduner

    Glamisduner Member

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    #4 Glamisduner, Jul 15, 2018
    Last edited: Jul 15, 2018
    SDG&E.JPG
    EV TOU here is
    $0.53773 peak, 0.28602 off peak, 0.22793 super off peak summer
    0.2479, 0.23885, 0.22879 winter.

    Peak hours are 4-9:00 when your not producing much, so you typically need to produce 115-125% of your total usage to compensate for TOU. This would at double the cost for the solar install and I don't have enough space on my roof for that anyways.

    You would save on charging the tesla at night, but running the AC when it's over 100 degrees would cost double. Of course if you don't have pets or people at home I'd be ok just running the AC after 7:00 or so, so as to not get dinged too bad, or just work till 7:00 or 8:00, but that's not the case for me.

    I'm thinking of the install as just another cost into the car. Good thing I didn't opt for the P model, an extra 18k to make charging affordable is no joke. I did know I would need to do something though, so thats on my and my poor decision to go EV in San Diego, and own an all electric house!

    So if the car get's 40 miles off 10kw, it's pretty comparable to paying $5.4 dollars for a gallon of gas/diesel in a car that can do 40mpg (my dad's e-250 for example) if charged in during peak hours (not typically the case but damn!). depending on how you want to calculate that. I mean technically I would be getting power for the car cheaper on TOU, but it just makes it so you pay more for power in other areas.

    However, since the car uses to much power it might be worth switching to EV TOU. It's extremely complicated and hard to calculate though :(
     
  5. ucmndd

    ucmndd Member

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    Based on the rates you posted above I assume you're SDGE. Those "super off peak" rates are high... here up north in PGE territory they're about half of that which makes the leap to TOU more cut and dry.

    Have you looked at the new EV-TOU-5 plan SDGE just announced? You pay a $16/mo "service fee" but it drops your super off peak rate all the way to 0.09/kwh. Might be worth it given your relatively high driving.

    Electric Vehicle Plans | San Diego Gas & Electric

    If you're gonna spend a lot of time up in the tier 2+ pricing range on your current plan, I think you'll find the economics of TOU start to work in your favor pretty quickly.
     
    • Helpful x 3
  6. Glamisduner

    Glamisduner Member

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    I had not heard of that one yet, thanks for the link. So our monthly usage is currently around 1300 kwh. That would nearly double the rate for the power I use in the daytime of course we get credited while producing, but drastically cheapen the amount I would spend charging the car. Interesting.

    I don't see the EV plans showing as available under my account, so I will have to call them monday and see if they can give me an estimate. Maybe I can tell them to just double current the nighttime usage rates, but I don't know if they actually have access to this information or just rely on their computers to relay the data.
     
  7. Kimo

    Kimo Member

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    Hmm, interesting, are you panels facing north? Running the nrel pvwatts tool (PVWatts Calculator) generaling 5.7kwh from a 4.6kw system would mean you panels are facing primarily north vs. the suggest south / west / east direction. If you panels are facing the recommend south (180 degree), a 4.6kw system, using standard panels, with 14% loss, and 20 degree tilt, should give you a kwh output range of 7,327 to 7,671 kWh. (I selected your city as the location.) But even with a E or W direction, you are still in the 6.5+kwh output on that type of system.

    What is your yearly kwh output of your current 7kw system? (Have you cleaned your panels recently to get any dust / dirt off?)
     
  8. Glamisduner

    Glamisduner Member

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    #8 Glamisduner, Jul 21, 2018
    Last edited: Jul 21, 2018
    My panels are facing west.
    Today (perfect day for solar) I peaked at 6Kw production 2kw on the 2.5kw inverter and 4kw on the 5kw inverter.

    Getting up early tomorrow to spray off the panels I haven't done that in a long time, but I doubt it will make much difference.

    I have been reading that you can typically loan inverters to 125% and I only have 6.9kw of panels. I'm thinking the cheapest upgrade will be to get up on the roof and add more panels myself.

    Trouble is, that I have no idea what I'm doing. I'm not sure how many can be in series together, but I guess 2 or 3, and then you put them into a distribution block (might require a new block) and that's it? I hate working on the roof though, the only place that sucks more in the summer is the attic :p
     
  9. Kimo

    Kimo Member

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    I wish I could be more help on the how aspect of adding additional panels to a system. You may want to jump over to the energy part of the forum, I am sure there are a few folks who could give you some guidance. (It is called Tesla Energy, but I see lots of discussions about Solar in general.)
     
  10. Piney999

    Piney999 Member

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    You definitely want to jump over to the energy section of the forum. There are some really smart folks lurking over there. NWDIVER is a forum member who really knows his stuff, and hangs out over there.
     
    • Like x 1
  11. ninpb

    ninpb Member

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    I'd be careful about disqualifying yourself from NEM1. Do you know if increasing without permit, notifying utlity is grounds for that?
     
  12. Glamisduner

    Glamisduner Member

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    If you get a permit they also disqualify you and that's a sure thing :p

    I'm pretty sure I will be switching to EV-TOU-5 when it becomes available. It provides $.09 Kwh from midnight to 6AM with a $16 a month additional service fee.
     
  13. Sandiegodoug

    Sandiegodoug Member

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    Sdge said I could increase system by 10%
    And still remain in nem 1. My system was installed before I had any ev’s, now I have 2 Tesla’s . I was going to add 3 more panels but this year got 2x500 bill credit so now I’m thinking not adding any, but also don’t want to miss out on fed tax credit. My installer also said when he increases systems, sdge never checks as long as you use the power.
     
    • Like x 1
  14. forkee

    forkee Member

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    just browsing the threads and came upon yours....

    here's my 2c....

    what you're paying for electricity even with solar is bonkers!

    I suggest moving to a TOU rate and getting a Tesla Powerwall. This is what I did.

    With the powerwall you can bank your energy at a lower rate after switching to TOU (usually in the morning) and then use same energy in the afternoon to bypass the higher rated times (you can set powerwall to only discharge during high peak times). This is most beneficial during summer when running the AC almost continuously. TOU also offers benefit of "super off peak" times at night. This is perfect for scheduling car charging, especially when super off peak rates are lower than the cheapest tiered rate. Also, after the powerwall is all juiced up, solar energy goes back to the grid (just like usual) but if you're on TOU, now it goes back at the same peak rate! It goes perfect with solar because that is when the panels are generating the most energy.

    Ultimately, most of my usage is on super off peak rates AND most of it gets offset by energy I generated at peak rates. For example, if i sent my electrical company (SCE) 100kwh of energy at peak times, it can offset 400kwh of energy I used during super off peak (or around 200kwh of regular off peak). The powerwall cost me about 8 grand total, but I did get 5800 back from SCE so it wasn't too big a hole in my wallet. If your electric company has similar incentives, this would be your best bet and far more affordable. You would also have electricity in the event of a blackout. My ANNUAL electricity bill stays around $200, and that's with A/C going nonstop during summer and the christmas lights blaring all december, lol. i have a 5kw system on a 1600 sq ft house.

    Anyways, I'll stop promoting now....but if you do decide on doing the same, use my referral code yah? ;)
     
    • Informative x 1
  15. Sandiegodoug

    Sandiegodoug Member

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    With an 11% increase coming January and now they are going to court to have us pay the 357 million for 2007 fires, not sure how any one without solar will manage bill in sdge’s territory.
     
    • Like x 1
  16. ceekz

    ceekz Member

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    We installed solar (Solar City) with the plan to generate about half the power used by our household two years ago, with an eye for future expansion. With the pending arrival of a Model 3, I checked into adding to array for more generation plus a Powerwall to charge off the grid at night. Tesla Solar said it would require an install of another complete system with separate meter and new agreement with our local provider. This pretty much took the option off my plate. The need for a totally new system was not included in the original installation discussion although growth was. glamisduner, are you able to add to your system or would it require a second meter?
     
  17. MorrisonHiker

    MorrisonHiker S 90D 2018.32.4

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    Do you already have two meters or just one? We just had solar installed by Tesla Energy and we'll have two meters once the utility comes out to install them. One is production only and one is production and consumption. I know someone else got solar installed a couple years ago and he didn't get the production meter installed. They just have the one meter that measures production and consumption.

    Maybe TE just meant that you'd need a production meter installed?
     
  18. Nocturnal

    Nocturnal Member

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    I'd be curious to know why he thought that. Your existing meter likely has a generation and delivery channel. Not sure why adding more solar capacity would change anything, unless messing with your existing system would be too difficult.
     
  19. Glamisduner

    Glamisduner Member

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    #19 Glamisduner, Aug 24, 2018
    Last edited: Aug 24, 2018
    I can't use a tesla power wall as it is a DC system. I'd have to go with a different brand that would work with AC inverters (that's what I was told anyways). However even though you have to overproduce and buy back power at a higher rate, it's still cheaper to add more panels than add a power wall. The power wall give your a backup source in case of an outage, but is not the best solution for lowering your bill. (or so I am told).

    I have decided against adding more panel until after I get a good year of usage on the charts to see where I stand with the TOU plan. I'm already paying a $240 a month HEL for the original 32 panel install. Also I'd be buying more efficient panels and putting them on less efficient portions of the roof. Home is only 1400 Sqft.

    I was up on the roof washing panels last month. I found 3 panels that need to be replaced (they are still producing but had fissures in them).
    [​IMG]2018-07-25_01-51-27 by glamisduner, on Flickr

    [​IMG]2018-07-24_11-55-14 by glamisduner, on Flickr
     
  20. Sandiegodoug

    Sandiegodoug Member

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    Emphase makes an ac battery system that pairs with micro converters. I was told that if your in nem 1, better to add panels until we are forced onto time of use by sdge. Your allowed 10%. So I would add 4.
     
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