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Years to breakeven..? PA Solar worth it?

Discussion in 'Tesla Energy' started by SabrToothSqrl, Feb 20, 2021.

  1. SabrToothSqrl

    SabrToothSqrl Active Member

    Joined:
    Dec 5, 2014
    Messages:
    3,613
    Location:
    PA
    Trying to do some math, and thinking out-loud; I've run the numbers a few times, and haven't yet found solar to be financially advantageous in PA.

    Tesla says I need a 16.32 kW system. $33,000 (plus 9k rebates).

    Over the last 3 years I average: 2,400 kWh/month. (No anticipated changes coming up). (Would love a hot tub).

    Here in PA, zip 17339, we have fairly cheap power.
    ALL IN (not just generation) over the last 3 years: $0.1025 / kWh

    I switch generation companies religiously to get the cheapest power.

    Anyway, in my zip code with not ideal sunshine and cheap power... is the payback really 10 years?

    Price After Incentives $23,185.

    Google says: 1,445 hours of usable sunlight per year x 16.32 = 23,582.4 kWh/year. 1,965/month.
    After Solar: 435 kWh/month from grid/average.

    1965 / 2400 kWh = 80% solar powered house.

    Grid Power: $2,952 / year
    Solar Offset: $2,361.6 / year

    $23,185 / $2,361 = about 10 years

    Of course this doesn't account for missed opportunity costs of the $23($32) upfront costs.
    I can do better than their 5% loan if I wanted to as well.

    So after 10 years, when the panels are "paid for by the reduced electric bill", I just have a super cheap electric bill for life then, at the property.

    Am I missing anything? 10 years seems reasonable for ROI for something for the house. Although it's a long time...

    At 10 years, saving $2,361/year starts, so 10 years of that is $23,610. 20 year panels.
     
  2. arnolddeleon

    arnolddeleon Supporting Member

    Joined:
    Jul 21, 2012
    Messages:
    637
    Location:
    SF Bay Area
    One of the ways I like looking at this is to calculate my per kWh cost with solar over whatever period I deemed as its lifetime (include cost of money, maintenance). You can think of solar as just prepaying for a bucket (with some uncertainty) of electrons. Rough numbers say solar is below $0.10/kWh. Given your low energy costs, 10 years to break even is not surprising. If you are modeling opportunity costs then you should also be modeling how energy prices are likely to change.
     
  3. DrSmile

    DrSmile Member

    Joined:
    Nov 7, 2018
    Messages:
    215
    Location:
    Northern NJ
    My electricity costs are twice yours, and I get SRECs which halves the payback period, and I calculate about 3.5 years payback with a slightly smaller system, so your calculations seem quite accurate to me.

    I would add that the Tesla estimates are typically conservative and you may want to check PVWatts for more accurate yearly production.
     
  4. Laketime

    Laketime Member

    Joined:
    Dec 13, 2020
    Messages:
    110
    Location:
    LI NY
    Are you likely to stay in the house for those 10 years? If so then I would look at is from a finance point of view. There are very few places where you can put your money and earn 10% tax free every year (which is essentially what you are getting).
     
  5. wwhitney

    wwhitney Member

    Joined:
    Nov 2, 2017
    Messages:
    731
    Location:
    Berkeley, CA
    Don't forget the personal utility of avoiding the unpriced externalities caused by using grid power. The utility (as in utility function) payback time should be less than the dollar payback time.

    Cheers, Wayne
     
  6. sorka

    sorka Well-Known Member

    Joined:
    Feb 28, 2015
    Messages:
    7,588
    Location:
    Merced, CA
    8.16 KW + 3 Powerwalls. I'm PG&E on EV-2A. My ROI payback is 6.8 years assuming I don't have any weeks long inverter failures in the middle of the summer. The interesting thing is that adding the powerwalls didn't increase the payback time hardly at due to the offset of eliminating 100% peak usage.
     
  7. smaster553

    smaster553 Member

    Joined:
    Feb 5, 2021
    Messages:
    46
    Location:
    New Jersey
    My numbers are as under:

    Historical Usage: 14800 kWh / year
    Installed Capacity: 14.28 kW
    Cost to install: $21,500 after rebate
    Cost of funds: 3.5% (HELOC) hopefully stays around here
    Cost of Electricity: 13.5c net
    TREC: $1470 / year (hoping I generate 16 mW)

    With these numbers I calculated years to payback at around 6-7 years. I will never put HELOC in any earnings investment as I want to keep my home.

    I think with these numbers my ROI is 16% and cost of funds is 3.5% so net 12.5% (tax free)
     

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