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  • is my project economically viable ?

    I've started at least two other threads seeking information about equipment for my DIY project, and people keep warning me of the likelihood that my project is not economically viable. So I'm starting this thread to discuss that subject.

    I plan to build a ground-mounted grid-tied system of approximately 5kw. I plan to do all the work myself. I've done quite a bit of carpentry and house wiring (and I am an electrical engineer); my county allows DIY, including electrical work, subject to inspection. I will build a simple wooden structure and use rails from someone like IronRidge for mounting (the structure will be used as semi-dry storage for trash cans, garden tools, etc).

    Using PVWatts, with these assumptions: DC size 4.8kw, standard panels with open-rack mounting, all system losses default except shading is 30% (for total losses of 38%), tilt of 30 degrees and azimuth of 172 degrees (slightly sub-optimal, at a cost of about 1/3 of one percent of production), I get 5044 kwh per year. The biggest question mark in this analysis is the figure for shading loss; this is the figure derived by a big installer, who gave me a quote with a guaranteed output using that number); also, I have the ownership and the ability to cut down problem trees.

    I'm estimating the cost as follows:
    $3145 for 15 Canadian 320 watt panels from (delivered from A1 Solar Store)
    $683 for 15 Tigo TS4-R-O optimizers(delivered from altestore)
    $1186 for SMA inverter (delivered from Renvu)
    $750 materials for structure
    $750 mounting rails and hardware ($50 per panel)
    $1000 miscellaneous supplies (mostly electrical)
    $200 permits
    $250 engineering seal for structure
    ... for a total of $7964, or about $5600 after the federal tax credit.

    So the bottom line is $1.10 construction cost per annual kwh of generation.

    I'm on a time-of-day rate, with net metering, paying about $0.30/kwh during peak (6-10am winter, 1-6pm summer) and about $0.05/kwh otherwise. In fact, my output will first be credited against my peak usage, and the remainder credited against my off-peak usage; all excess production will be credited at the off-peak rate. I calculate a return of about $368 per year. For a payoff slightly less than 14 years (ignoring the time value of money, and the increase in my house's value). Also, our rural coop will get improved metering equipment in "a few years", at which time excess production during peak hours will be credited at the peak rate.
    Last edited by RShackleford; 11-03-2019, 09:33 PM.

  • #2
    Do you have the discipline to restrict your usage during TOU hours, to have effective credit ? Some TOU plans extend till 8 or 9 pm, well past dark.

    What plans will you be offered when you change from "now" to Solar ?

    Having heavy loads like dishwashing and laundry happen in the "off" hours will help your payback, but the same efforts will help with your plain billing.

    Since there is the issue of shading, shade generally renders panels useless. if you expect ANY shade from 10am - 2pm standard time, you should rethink the site or remove the offending trees
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment


    • #3
      Originally posted by RShackleford View Post
      For a payoff slightly more than 10 years (ignoring the time value of money, and the increase in my house's value).
      That sounds like it's borderline economically viable to me.
      If it were much worse I'd probably not.
      I'd probably want to have 1 source for the modules and inverter and such rather than 3.

      Comment


      • #4
        Originally posted by foo1bar View Post
        That sounds like it's borderline economically viable to me.
        If it were much worse I'd probably not.
        I made a math error (and edited OP); it's actually more like 14 years.


        Comment


        • #5
          When the coop starts crediting peak-hour production at peak rate, things look a bit brighter. Since solar noon here is about 1:15pm in the summer, and peak hours are 1-6pm on weekdays, I'm gonna assume 36% of summer production is during peak (half of production for 5/7 of the days). In winter, solar noon is 12:15pm and peak hours are 6-10am, so I'll assume none of the production is at peak. If I additonally assume production is split evenly between summer and winter, that means 18% of production is peak (summer peak rate of 33 cents). So my average kwh is worth about 10 cents, or about $500/year, so back close to a 10 year payoff.

          Comment


          • #6
            Originally posted by Mike90250 View Post
            Do you have the discipline to restrict your usage during TOU hours, to have effective credit ? Some TOU plans extend till 8 or 9 pm, well past dark.

            What plans will you be offered when you change from "now" to Solar ?
            Same plan as now, except for net metering. I've been living with the same peak plan for some years now and it works well. Very little activity 6-10am in summer. Like to sleep cold, so keep house chilling overnight, and it remains comfy during 1-6pm summer peak. Water heater is on a timer.



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            • #7
              Originally posted by foo1bar View Post
              I'd probably want to have 1 source for the modules and inverter and such rather than 3.
              Why ?


              Comment


              • #8
                Originally posted by RShackleford View Post
                When the coop starts crediting peak-hour production at peak rate, things look a bit brighter ... so back close to a 10 year payoff.
                So at some indeterminate time in the future, I may get to that 10 year payoff rate. Not so great.

                So, I think it boils down to the issue of whether or not the panels add value to the house. Lots of likely-biased articles (solar vendors etc) say they do. This article seems even-handed though: http://money.com/money/5642057/home-value-solar-panels/ . And this gov't study actually includes my area, and suggests it'd add at least double the value of my estimated cost: https://emp.lbl.gov/sites/default/fi...nl-1002778.pdf


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                • #9
                  "I'd probably want to have 1 source for the modules and inverter and such rather than 3."
                  Originally posted by RShackleford View Post
                  Why ?
                  "One throat to choke"

                  When/if there's a problem, it isn't "well my stuff is perfect, it must be what you bought from the other guy"

                  Comment


                  • #10
                    Originally posted by RShackleford View Post
                    ............ I think it boils down to the issue of whether or not the panels add value to the house. Lots of likely-biased articles (solar vendors etc) say they do.......
                    It only adds value if the Buyer is educated enough to understand it can benefit them. Who's going to educate the buyer ? I had to educate my sales agent, after he sold my house for MY asking, he put panels on his own house.
                    I had a well thought out GT system in Los Angeles, which nearly zeroed out my bill, and had copies of the bills before and after to prove it. $0 vs $150 (in 2003 dollars)

                    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                    solar: http://tinyurl.com/LMR-Solar
                    gen: http://tinyurl.com/LMR-Lister

                    Comment


                    • #11
                      Originally posted by Mike90250 View Post

                      It only adds value if the Buyer is educated enough to understand it can benefit them. Who's going to educate the buyer ? I had to educate my sales agent, after he sold my house for MY asking, he put panels on his own house.
                      I had a well thought out GT system in Los Angeles, which nearly zeroed out my bill, and had copies of the bills before and after to prove it. $0 vs $150 (in 2003 dollars)
                      Or, as I've seen more often on a local level, and similar to a lot of the posters I see around here, residential PV may add perceived value if the buyer is uneducated enough to let others with skin in the game oversell the benefits and swallow the hype - a lot of it from friends and neighbors who are equally ignorant, and/or from sources such as the green wash media shills of the solar peddlers.

                      Reality is, folks see what they want to see, hear what they want to hear, and read what they want to read. Generally, what is portrayed as making life easier is easier to sell, objectively true or not.

                      Ignorance is the real enemy.

                      Comment


                      • #12
                        Originally posted by Mike90250 View Post
                        It only adds value if the Buyer is educated enough to understand it can benefit them.
                        The area where I live is highly-educated. And there is a LOT of solar around, so people know what it is and are used to seeing it.

                        It's still a stretch to install a system where I'm depending on a likely increase in property value to make it economically viable. OTOH, since DIY I'll be paying about half of what the system would cost if installed by a company (what are people typically paying per watt for a ground-mount system in the 5kw range ?)


                        Last edited by RShackleford; 11-04-2019, 01:09 PM.

                        Comment


                        • #13
                          Originally posted by RShackleford View Post
                          The area where I live is highly-educated. And there is a LOT of solar around, so people know what it is and are used to seeing it.

                          It's still a stretch to install a system where I'm depending on a likely increase in property value to make it economically viable. OTOH, since DIY I'll be paying about half of what the system would cost if installed by a company (what are people typically paying per watt for a ground-mount system in the 5kw range ?)

                          In what ways are they "highly educated" ? Being able to identify a horse from a steer doesn't make one a good horse breeder or an equestrian.

                          You want to play it safe on value added ? Assume a PV system will add nothing to a home's value and in so doing have a higher probability of being be pleasantly surprised when/if you sell.

                          Or, sort of like the B.S. of eggs are good/bad for you, don't start a chicken ranch in your back yard and assume the eggs you get will be in favor or that the exercise will add any value to your property if/when you sell it.
                          Last edited by J.P.M.; 11-04-2019, 02:57 PM.

                          Comment


                          • #14
                            Originally posted by J.P.M. View Post
                            Being able to identify a horse from a steer doesn't make one a good horse breeder or an equestrian.
                            well maybe a Stallion from a Gelding would help but horse from steer is equine to bovine simple.
                            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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                            • #15
                              Originally posted by RShackleford View Post
                              It's still a stretch to install a system where I'm depending on a likely increase in property value to make it economically viable.
                              No one should be using the possibility of increased home value in a ROI evaluation. If the ROI looks so bad that you have to start adding variables like "increased property value" to make it seem logical, you should not be going solar.

                              Dave W. Gilbert AZ
                              6.63kW grid-tie owner

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