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  • pay-back time

    I can't really make sense of the payback time. The calculator says I will generate 4,498 kWh/yr at an average cost(value) of $.41/kWh So that is $1844/yr that I save. The system cost after rebates is $8,624 So I calculate the payback time as $8624 / $1844 = 4.68 years. But the Calculator says 2yr 8 mo Why are my numbers off?

  • #2
    The real question is what size system?. Go to PVWatts yo put in your location and system size to get another opinion about kWhr production. Maybe it assumes pretax numbers. Is that $0.41/kwhr the rate the power company will pay you all day and weekends?
    9 kW solar, 42kWh LFP storage. EV owner since 2012

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    • #3
      Originally posted by mckennatim View Post
      I can't really make sense of the payback time. The calculator says I will generate 4,498 kWh/yr at an average cost(value) of $.41/kWh So that is $1844/yr that I save. The system cost after rebates is $8,624 So I calculate the payback time as $8624 / $1844 = 4.68 years. But the Calculator says 2yr 8 mo Why are my numbers off?
      Looks like the way whatever calculator you're referring to is calculating whatever you call payback time is using different methods and parameters than you are.

      A lot more information will be needed from you before I, at least, can make any sense of what you write. Whatever calculator you are referring to may be using some time value of money calculations, tax savings and resale value or several other parameters that you are not using. Either number, or both may or any other calculated system valuation or method may not be realistic, depending on whoever is paying the bills thinks is a good number. That opinion, in turn, may or may not be a realistic reflection of reality for the situation. Process economics is not an exact endeavor.

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      • #4
        Originally posted by J.P.M. View Post

        whatever calculator you're referring to is .
        https://www.solar-estimate.org/solar...lators/results

        and I am sure you are right. They probably factored in SMART whatever that is

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        • #5
          As far as I can tell the solar-estimate.org website is just a way to generate leads and sell the leads to middlemen who subcontract out to installers.
          Maybe I'm wrong - but when it won't give me any information without an email address *AND* a phone number, it looks pretty much like a scam to me... A way to get my info so that they can sell it to telemarketers.

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          • #6
            Originally posted by foo1bar View Post
            As far as I can tell the solar-estimate.org website is just a way to generate leads and sell the leads to middlemen who subcontract out to installers.
            Maybe I'm wrong - but when it won't give me any information without an email address *AND* a phone number, it looks pretty much like a scam to me... A way to get my info so that they can sell it to telemarketers.
            I notice a similarity in Logos with this Forum and that site. Perhaps they cover the expenses of hosting this Forum so they can get leads. Anybody know the connection. Just a coincidence?
            EDIT: Got the answer. They pay for hosting this site. That is a good thing.
            Last edited by Ampster; 09-03-2019, 06:46 PM.
            9 kW solar, 42kWh LFP storage. EV owner since 2012

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            • #7
              Originally posted by foo1bar View Post
              As far as I can tell the solar-estimate.org website is just a way to generate leads and sell the leads to middlemen who subcontract out to installers.
              Maybe I'm wrong - but when it won't give me any information without an email address *AND* a phone number, it looks pretty much like a scam to me... A way to get my info so that they can sell it to telemarketers.
              Well you would be wrong, the solar estimate calculator is just that, and yes the reason you have to put in a phone number and email address is so they can sell a lead potentially to a solar company, its no scam, and these are the people who pay to keep the lights on around this place, no solarestimate.org and no solarreviews.com would mean there would have been no solar panel talk. It is what it is

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              • #8
                Originally posted by foo1bar

                Ok... How am I wrong?

                You just restated what I said.

                Is it that you disagree with the word scam?

                I stand by the characterization of surreptitiously taking the phone # and email address of someone and selling it to a telemarketer is a scam.


                Even if it helps pay for the server and bandwidth for this board, I think secretly taking the phone # and email to sell them to a telemarketers is not a good thing.
                FWIW, I'm mostly w/ foo1bar on this one. You say he's wrong and then in effect, confirm as correct that which he wrote.

                It's a lead generator and little else as I've pointed out several times over the last 6 years or so. The bait of the solar estimator is just that - bait - and something easily obtained, ironically, on this forum, and by spending about 20 min. with the PVWatts help screens. That's were I was planning on taking the OP in my opening post to this thread if I could get a bit more information from him.

                The lead generator concept used here is not much different than offers of free and mostly useless stuff for a simple phone call with the result of a lead (or "mark" is a pejorative commonly used in the peddling trade I spent about 10 years in) that has marketing value and can then be monetized. The method has been around for probably centuries.

                The smelly end of the stick this is, at the very least, that most folks are probably clueless that their personal information is being sold like meat and their privacy is being treated as a commodity.

                Such are the realities of life. I get that and some of the rest of life's realities. But life would be just as real if somewhere in very plain sight on all the solar reviews hype and advertising there was a clear and unambiguous notification that if you provide personal contact information it'll be sold and some peddler will likely be harassing you very soon.

                As for keeping the lights on - yes it probably does. But my guess is that if SPT operated at a loss it would not be around or not have lasted as long as it has.

                Also, and I've got absolutely no way to know this, but the task of keeping the lights on may, perhaps be just a bit more profitable by the reputation (such as it may be) SPT has from having input from some pretty savvy technical folks, including quite a few P.E's and more than few experienced solar professionals who tend to tell it straight - all for gratis, and (BTW) all the time never asking for any personal information.

                I get that this is not a public service outlet. I get the profit motive and lights on and all the rest. It's a business. But a bit of honest, straight disclosure that the solar reviews site is primarily a lead generator might be considered a class act.

                So have some class and take the high road.

                Hell, you've just stated it's a lead generator. Take it the rest of the way for those who are na

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                • #9
                  Originally posted by solar pete View Post

                  Well you would be wrong, the solar estimate calculator is just that, and yes the reason you have to put in a phone number and email address is so they can sell a lead potentially to a solar company, its no scam, and these are the people who pay to keep the lights on around this place, no solarestimate.org and no solarreviews.com would mean there would have been no solar panel talk. It is what it is
                  Where does the money go after those costs are covered?
                  I don't really mind but it would be interesting to know.

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                  • #10
                    Originally posted by Elemental101 View Post

                    Where does the money go after those costs are covered?
                    I don't really mind but it would be interesting to know.
                    That is a question for Solar-Estimate. I assume the Administrator only has knowledge of costs associated with this forum unless he has some business relationship with Solar-Estimate.
                    9 kW solar, 42kWh LFP storage. EV owner since 2012

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                    • #11
                      Originally posted by solar pete View Post
                      Well you would be wrong, the solar estimate calculator is just that, and yes the reason you have to put in a phone number and email address is so they can sell a lead potentially to a solar company, its no scam, and these are the people who pay to keep the lights on around this place, no solarestimate.org and no solarreviews.com would mean there would have been no solar panel talk. It is what it is
                      Hey Solar Pete, you probably need to have someone take a look at the server.
                      It seems my previous post responding to this one has disappeared. I assume that there was a database error or something.

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                      • #12
                        Originally posted by foo1bar View Post

                        Hey Solar Pete, you probably need to have someone take a look at the server.
                        It seems my previous post responding to this one has disappeared. I assume that there was a database error or something.
                        FWIW, your post showed up in my post that was responding to your referenced post. If your post got deep sixed, maybe mine will too.

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                        • #13
                          I had some missing posts also. No worries, I understand this is not a democracy.
                          9 kW solar, 42kWh LFP storage. EV owner since 2012

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                          • #14
                            I recently ran an "estimate" using the forum's calculator and it also provided a much quicker payback then it should have. I asked Pete about it and he had the IT department make some changes. I reran the calculations and the payback fell almost dead nuts on what I had calculated using a different calculator.

                            I have no issue providing contact information for a solar contractor to get in touch with me. It seems like the correct next step in using a calculator for free. So providing that information is not wrong or a scam in my book if it means keeping a company in business.

                            As for receiving an aggressive payback value. Maybe the forum calculation software still needs some tweaking.
                            Last edited by SunEagle; 09-04-2019, 05:43 PM.

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                            • #15
                              Originally posted by SunEagle View Post
                              As for receiving an aggressive payback value. Maybe the forum calculation software still needs some tweaking.
                              If so, might I respectfully suggest as something to pass along to the powers that be that it might be a considerate and prudent thing to do to remove the suspect calculation software until it's examined for errors ?

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