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Number crunching

Discussion in 'Fred's House of Pancakes' started by Leadfoot J. McCoalroller, Apr 22, 2022.

  1. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Still stuck at 75% production.

    I have to think that my electrician is suitably motivated to correct this as his final (substantial) payment awaits as per our contract. He really wants his supplier to manufacture a new custom cable and ship it to him, and they want him to re-work the existing one. He's the face of a 25-year warranty on the item, so I like his dedication in the pursuit.

    Despite this production limit, it was pretty cool to take note the other day as I did that while we had 3 rooms air-conditioned, the clothes dryer tumbling and a pan cooking on the range, we were still net-export, pushing power to the grid.

    Of course that's exactly what it's supposed to do at this time of year... just going to take a little getting used to.
     
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  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    My electrician made it back out this morning and corrected the bus cable that was preventing the last 5 inverters from participating.

    I never did hear what type of electrical fault was causing it, but he's got it working the way it should be. Today's peak production was substantially higher as a result, hitting 88% of nameplate rating in between the clouds.

    Naturally, we have some stormy weather ahead so it may be a while before we really see this thing go to the max.

    Meanwhile the meter says that we are consistently making more than we are using- exactly as planned for this time of year. We expect to widen that gap now with the last quarter of the array performing.
     
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  3. Louis19

    Louis19 Active Member

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    That is good news , :) I will follow your results
     
  4. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    +1.
    I'm interested in the final per average kw/h cost if it can ever be ascertained including tax kickbacks.
    I take it as an article of faith that the Commonwealth of Pennsylvania will kick in a few 'GREENbacks' and this will be another local variable for those playing along at home.
     
  5. Salamander_King

    Salamander_King Senior Member

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    Are you asking the installation cost of $/kW based on the system size? Or are you asking actual production cost of $/kWh? The former is easily calculable, even before the actual installation. I now have 7 quotes ranging from $2.50/W to $4.10/W to install a system at my location. After 30% tax credit, they will be $1.75/W to $2.87/W.

    But if you are asking about the actual production cost of $/kWh. It would be difficult without making some assumption such as, life of the panel, yearly degradation, and annual total production. Basically, the real kw/h cost would be a ((total cost of the system for the life. this includes upfront installation cost or total payments if financed and any maintenance or repair costs later if needed)-(any incentives paid back)) / (total amount of kWh electricity produced for the life of the system). But it would be very difficult to calculate this number accurately without waiting until the end of the service of the system 30 or more years.
     
    #385 Salamander_King, May 31, 2024
    Last edited: May 31, 2024
  6. Salamander_King

    Salamander_King Senior Member

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    I think it is much easier to estimate the pay back period than trying to guess the cost per kWh. The ROI in terms of saving in the cost of the electricity will eventually reach the total cost of the initial installation. At that point, any electricity consumed up to the total electricity generated become free. The system does not have to be a Net Zero for this to happen. As long as I can recover the initial cost by saving on the utility bill before the end of the life of the system, I gain $$$ saved by not paying the utility bill after reaching the pay off point. In my situation, if the system performs as designed about 90% offset of our current consumption, then the pay off period is anywhere from 7-9 years. As long as the system keeps producing for 25 years, the net saving (that is total saving minus the initial cost) is roughly $100,000. If the system keeps working more than 25 yrs and/or the electricity rate goes up more than 4% annually, then the saving will increase even more.
     
    #386 Salamander_King, May 31, 2024
    Last edited: May 31, 2024
  7. Salamander_King

    Salamander_King Senior Member

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    I did more math...
    The figure I commented on above works for my case. That is... A) $0.32/kWh electric rate and B) 1100kWh/mo consumption, and C)~$30K for 14kW solar system installation after incentive. Plus, most importantly, D) the state utility must pay 1:1 credit for every kWh generated via Net metering billing. I know some states do not offer this.

    If any of these numbers are shifted then ROI estimation will shift. For example, if the rate is decreased to $0.2/kWh, then the payback period will increase from 7 years to 11 years. And if the rate stays at this low, at the end of 25 years, the Net savings will be only ~$36,000 instead of $100,000 with the current rate of $0.32/kWh and increasing annually at 4%. That would be equivalent to investing $30,000 today and receiving compound interest of 3.21% rate for the next 25 years. Hardly the best investment vehicle for money. That's why solar panels did not make much financial sense to me a few years ago when the rate was around $0.2/kWh. Only in the last two years with above $0.3/kWh rate and still increasing, finally the solar started to make some sense. BTW, even with the $100,000 Net saving in the 25-year scenario mentioned above, it is still only about a 6.2% annual return rate.

    So, as an investment, for most people who pay close to the national average rate of electricity at $0.17/kWh or less, solar panels would not be a good investment. You would likely have more money at the end of 25 years with $30,000 invested in fairly safe investment vehicle such as bonds or CDs, or even in high-interest savings.
     
    #387 Salamander_King, May 31, 2024
    Last edited: May 31, 2024
  8. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    It's good to recognize this.

    About all I can say here is that the relentless pursuit of maximized investment returns is the most environmentally destructive force I've ever witnessed. It's kind of why I need solar panels in 2024.

    Most of my other investments are much more ruthless and destructive than solar panels, but... it's a start.

    I get to explain this all to my kid someday.

    [​IMG]
     
    #388 Leadfoot J. McCoalroller, Jun 1, 2024
    Last edited: Jun 1, 2024
  9. Salamander_King

    Salamander_King Senior Member

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    I agree 100% with the first part of the statement. But, the solar industry is no different from any other companies. Their aim is to maximize the profit. There is no other purpose. I don't know about your state, but in our state, 1:1 Net meter billing on solar is shifting the cost to credit those with solar to the rest of the ratepayers. Those who do not have the resources to install solar are paying more to a few who have the resources to put the panels on top of the roof.

    And for those people who have resources, unless it is an off-grid self-sustained system, the bigger the system tied to the grid and the more electricity the house consumes, the quicker ROI one can accomplish. That is why almost all the solar companies I have inquired about ask "What is your monthly electricity bill" as the very first step. If the monthly bill is less than $100 (which means less than 320kWh/mo electricity usage at our current rate but it applies equally to a place with very low rate) it makes no sense to invest in the technology because pay back period is just too long.

    Here is an email I just received from one of the Solar companies... It sounds like the electricity rate hike is out of control. That's why the solar is now. The ads continued saying, "Take charge of your energy costs and gain independence from utility monopolies with solar power today. Enjoy the lowest prices in the nation and start saving." But the irony is that the more people jump on the bandwagon, the more expensive the electricity will become for the rest of the ratepayers. This is not a utilitarian system that benefits the majority.

    Screenshot_20240601-052919.png
     
    #389 Salamander_King, Jun 1, 2024
    Last edited: Jun 1, 2024
  10. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I didn't invest in solar because I think they're playing any nicer than any other industry. I don't see them as much different.

    I'm the one playing nicer. I'm saying that I'm personally willing to take a lower return on this investment, relative to what is possible elsewhere.
     
  11. Salamander_King

    Salamander_King Senior Member

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    I understood that part. People's motivation is not always for a higher return or more savings. I have purchased a PHEV not so much for saving or ROI but for trying to reduce gas usage. After my first PHEV 2017 Prius Prime, it was obvious that at our local cost of gas vs electric, driving a car on electricity did not save any fuel cost compared to driving a highly efficient gas car. But still, with incentives, it made financial sense to buy a PHEV and keep plugging in and drive it as 60% EV and 40% HV paying a bit more on fuel cost than if I had a pure HV counterpart.

    But as with the purchasing of the PHEV, purchasing solar would not be the best investment strategy if one's goal is only to maximize the ROI. My point was that solar companies in general are trying to persuade consumers to buy into the trend by appealing to either the "huge" savings or environmental benefits, or both. But that marketing works only for a select few who have resources and willingness, not for the majority. I just have to wonder if those who bought solar got the benefits either financial or environmental or both that were promised?
     
  12. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Well, we've already replaced our monthly energy payment with a monthly loan payment. And, we are darn close to 1:1 on that swap.

    Loans eventually get paid down, energy costs keep going up. The math was already good for us from the get-go, and it looks like it'll improve.

    About the only way this becomes a financial mistake is if electricity prices drop a lot and stay low a long time. And that's not such a bad problem to have.

    As far as environmental benefits? Well, I feel good that we have eliminated a lot of petroleum usage. Much more than we would have if we'd put the same money into buying a PHEV or EV.

    On the other hand I'm still living on the same planet that I'm busy ruining with all my other activities. It's going to be up to our descendants (if any) to determine that score.
     
  13. vvillovv

    vvillovv Senior Member

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    I still keep my solar project on a back back burner. I could fit a little over 9kWh of panels on the 10 square east west facing roof and possibly more on the detached garage that has the most south facing all day sun year round space in front of it, again an east west facing gable roof. And I still look for new ideas about how to and when to get serious. But first I have to upgrade the ole 1960 120 Amp split bus service panel. Not sure how many more years we will be in this house but so far it works pretty darned good comparatively speaking.

    On the other side of the coin. lets take a look at how society is handling things these days and wonder?


    Plus, anyone have a weather crystal ball showing what patterns are going to show up in the next 10 years? 5 years? This year?
     
    #393 vvillovv, Jun 1, 2024
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  14. Salamander_King

    Salamander_King Senior Member

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    How much more do you think? I don't know a good resources to calculate that.

    My current grid electricity is already 100% renewable. So doing solar will not reduce any emission. In fact, I have to cut a few healthy trees to get a solar to generate better. That's a negative environmental impact.

    On the other hand, the PHEV has cut down our gas usage by 60%.

    EDIT: I just remembered that you went to full heat pump. Yes, that would be a huge cut on the fossil fuel use. But for added cost.
     
  15. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    The latter.
    ROI does not interest me since I'm part of an electrical Co-Op, and I live in the SE.
    This means that any PV system would have the approximate ROI of my new GMC pickup.

    I will need to make some educated guesses about what my initial expenses will be and using other people's real-world numbers will make my initial presumptions a little more accurate.
    My plans are still gauzy at present but I'm imagining a DIY self-funded and cash flowed rooftop system at 1.25-1.5% of my average daytime needs.
    If I meet my clan's average male life expectancy my system will be about 20 years old when my estate is probated so it will add a little bit of value to my property - but the tech AND the panels and inverters will have aged by then greatly reducing its real-world street value.
     
  16. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I'm sure I posted the raw details up-thread somewhere, but our winter heating was using around 3x as much fuel as all of our driving in 2 cars.

    There's probably a more detailed answer to be calculated somehow, but this was already enough to sell me.
     
  17. vvillovv

    vvillovv Senior Member

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    I just ran the numbers for the homes EUI for the last 3 years.
    What is Energy Use Intensity (EUI)? | ENERGY STAR

    and IF ! I got the conversions correct I'm averaging around 10.22 - which looks to me like it's pretty good. There are only a few EnergyStar rated appliances in the house, most of which I installed 10 or 20 years ago.
     
  18. Salamander_King

    Salamander_King Senior Member

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    I can't speak for your specific system and situation, that would be a case-by-case scenario. But if I take the estimate from one of the quotes, the 14kW system costing ~$30K after incentive will produce ~13,000kWh annually. The panel degradation is minimal in that only a few percent drop in the first year then less than 1% annual degradation rate for the rest of life. That means even if the panel degraded to 80% level at the 25-year mark, the average production is 90%.

    So, conservatively, the system will generate 13,000kWh/yr x 0.9 average degradation over years x 25 years = 292,500kWh total generation. Divide the $30,000 system cost (assuming there is no additional maintenance or repair bills for the 25 years) by 292,500. I get $0.1025/kWh. That is about one-third of the rate I pay now. Of course, if the system continues to generate beyond the 25-year mark, then this rate would get even better. On the other hand, if the system does not produce as promised or causes additional costs that are not covered by warranty then the final rate will be higher. But again, that is a lot of if-and-but...

    Yes, eliminating heating oil is a huge benefit to the environment for sure. But you have accomplished that already when you installed the heat pumps without solar panels. Solar panels are not needed to operate the heat pumps. So, attributing that environmental impact to the solar is somewhat misleading.
     
    #398 Salamander_King, Jun 1, 2024
    Last edited: Jun 1, 2024
  19. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I'll grant you that it's not the whole picture, but we don't have to work hard to find even more satisfaction. My utility supply is roughly 60% fossil at any given moment.

    So I've eliminated significant petro use on-site, reduced the overall amount of energy needed for winter comfort by nearly 2/3 and then for good measure eliminated the need for fossil burning for 60% of that demand.

    For bonus points we can toss in cooling. The PV rig is working wonders at running air conditioners directly vs. running on the 60% fossil blend.

    We have traditionally spent more on cooling the house than we have on fueling the cars, if you look at any given hot month.
     
  20. Salamander_King

    Salamander_King Senior Member

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    After a lengthy "Number crunching" and comparison analyses among ~10 different solar installer's proposals, I finally picked the one. Not the cheapest, not the most expensive, but one I think is the best value by taking into the consideration warranty and production rating of the panels. The difference in cost among proposals was huge. The least expensive one was 33% less than the most expensive one. I ended up picking the middle-of-a-pack regional company with very good reviews and a strong foothold in the New England region.

    Just signed my life away. lol Yeah, as a single item/service purchase, it is the second-largest after a house purchase, surpassing the most expensive car purchase. It will be a 14.875 kW solar system, and with their estimated annual production, it should be paid off in ~9 years. If the system generates NERL estimated kWh, then the pay-off period would be shortened to 6.5 yrs. But even if everything moves as quickly as possible, I won't see the first production until late fall, so not likely to get much solar credit this year. Will see, how the project goes. Wish me luck.
     
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