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  • New to Forum & Solar - I have a choice to make...

    First I want to thank people who contribute to this board, I've learned a tremendous amount by just reading these forums over the past year - thank you. I started with the dummies guide, and went directly to reading this board.

    I live in Northern California, East Bay and it can get intensely hot and sunny in the summer months. I'm in the process of taking proposals for Solar on my primary residence. Looked into the leasing but decided purchasing was a better option. Some specs about our home: 2 story house, tile roof and located in walnut creek, CA. Our annual energy usage is between 11-15kWh (last three years) and I'd like to try and offset my energy with 100% solar, if possible. I have multiple roofs so the quotes presented have panels on both the east and west facing roof. I've spoken with multiple companies and received multiple quotes, all which cover 100% off my energy needs and narrowed it down to the 3 quotes below:

    Option 1 (Company A): [/w Optimizers]
    (26) Sunpower SP 320 panels = 8,320W (1,100KW monthly)
    Inverters: SE7600A-US w/ Optimizers
    26 split between two roofs
    Price: $35,680 before $500 coupon, $500 Armed Service coupon, $1,360 state, $720 Dealer special = $32,600 then 30% federal = Net = $22,820
    Price/Watt is $3.91/w before federal and $2.74/W after federal

    Option 2 (Company B) [/w Optimizers]
    (33) SolarWorld SW290 Mono = 8,378 (1040KW monthy)
    Inverter: SE7600A-US (240v) w/ Opimizers
    also split between roofs
    Price: $30,152 before 30% federal = Net = $21,107
    Price/watt is $3.59/w before federal and $2.51 after federal

    Option 3 (Company C) [/w Microinverters]
    (24) Sunpower SPR-X21-345-C-AC = 8,280 (11,573KW monthly)
    (24) Micro inverters - 96 cell GEN 3.0-HV-208/240v
    12 on each roof.
    Price: $35,500 before 30% federal = NET = $24,850
    (there might be an additional $1,500 if my employer is still part of the affiliate program - TBD)
    Price/watt is $4.28/w before federal, and $3.00/w

    Warranties for:
    Option A: 25 years (SE inverter would be extended to 25)
    Option B: 20y Product, 25y production, inverter 12y + $500 for 25Y
    Option C: is from Sunpower direct, 'assuming' 25y bumper-2-bumper

    Option B is the cheapest with 33 Solarworld Panels, gotten from an independent dealer with excellent yelp reviews. Option A is also interesting in that its only 26 panels and made by SunPower. I'm currently debating, micros vs. optimizers and pairing older SPR panels with SE optimizers and Inverter.

    Any input would be appreciated. Thanks
    Last edited by JRqwertyui; 05-09-2017, 05:29 PM.

  • #2
    Never lease, never buy Sunpower. Never oversize an array. Read "Solar Power Your Home for Dummies". Stay local w/established vendors and chose your vendor wisely. Don't do anything until you get more education about PV and how to conserve and reduce loads before you get PV.

    See prior threads for reasoning behind above statements.

    Comment


    • #3
      Thank you JPM,
      read the dummies guide cover 2 cover. Are you suggesting stay away from SPW panel only system, other components are solaredge. Or are you suggesting not buying the system from sunpower or their dealers? Also what constitutes an established vendor. They will all tell you "we've been in bussines for X years, with X in sales, covering X territory.
      Last edited by JRqwertyui; 05-09-2017, 06:56 PM.

      Comment


      • #4
        Originally posted by JRqwertyui View Post
        Thank you JPM,
        read the dummies guide cover 2 cover. Are you suggesting stay away from SPW panel only system, other components are solaredge. Or are you suggesting not buying the system from sunpower or their dealers? Also what constitutes an established vendor. They will all tell you "we've been in bussines for X years, with X in sales, covering X territory.
        Sunpower panels are fine products, but in terms of their annual output, reliability and annual degradation, they are not worth the ~ 15 - 25 % up front premium they put on a system price. MAYBE 5 %, but no more. I am also biased toward string inverters and not a fan of putting electronics in harsh, uncontrolled environments (like a rooftop) where they are less accessible as, for example, a string inverter in the semi controlled environment of a garage. Sting inverters also mean fewer parts to fail. I'm also generally not a fan of DIY and favor reliable, established electrical contractors as vendors over "Larry with a ladder" type vendors. Lastly, The smart money looks at long term value and most bang for the buck rather than simply lowest initial cost. A fair price, fairly, but toughly negotiated for a quality, fit for purpose product is a better deal than cheaping out on equipment, and hammering the vendors on initial price to the point where they feel justified in doing shoddy work that they bury, never to be seen until much later.

        Comment


        • #5
          I agree, I'd rather not have any electronics on the hot, humid, rain whipped, weathered roof. however, given my roof shading (east, west) orientation I'll opt for optimizers (thinking a good compromise between mirco's and string). I'm just not a fan of placing 33 panels (solarworld) when I can opt for 26 (SPW) while all other components are same. Are there other panels not made in China I should be considering ?
          Last edited by JRqwertyui; 05-09-2017, 08:12 PM.

          Comment


          • #6
            Option 4 (Company D): [/w Optimizers]
            (35) Canadian Solar CS6K-275M 275kw = 9.625kw
            Inverter: SE7600A-US (240v/40A) w/ Opimizers
            Price: $28,026 before 30% federal = Net = $19,618
            Price/watt is $2.91/w before federal and $2.03 after federal

            I was told panels are made in China...This is the least expensive system I've been quoted. 25 Year Warranty on panels, inverter and all labor. Asking vendor for info on production warranty, and liability insurance for roof.

            I'm also having them quote for LG panels instead of the ones made in China.
            Last edited by JRqwertyui; 05-09-2017, 09:31 PM.

            Comment


            • #7
              Originally posted by JRqwertyui View Post
              I agree, I'd rather not have any electronics on the hot, humid, rain whipped, weathered roof. however, given my roof shading (east, west) orientation I'll opt for optimizers (thinking a good compromise between mirco's and string). I'm just not a fan of placing 33 panels (solarworld) when I can opt for 26 (SPW) while all other components are same. Are there other panels not made in China I should be considering ?
              Then use string inverters. If both, east and west orientations are used and each array is not partially shaded, as by trees for example, string inverters are available to handle such situations, or two string inverters are also an option, bit at some extra cost. If you are saying partial shade is, for example, when an east facing array at a high tilt is entirely shaded in the mid/late afternoon because the solar profile angle is less than the roof tilt, optimizers or micros won't help that situation. They will help partial array shading. How much ? A shading analysis may be called for.

              Aside from the electronics on the roof, it's not the number of panels that matters. It's the array Wattage that counts, and Sunpower is not cost effective or more reliable in any way that counts. Just more money.

              Solar PV is an appliance and a commodity, not a lifestyle. A Mercedes and a Ford are equally fit for purpose as grocery haulers. Solar panels can be thought of in a similar way, except a Sunpower PV system will add little to zero extra resale value to your home, if any resale value as may be the case.
              Last edited by J.P.M.; 05-10-2017, 12:22 AM.

              Comment


              • #8
                Please let me make sure I understand, I'm still new to Solar. In the early morning and late afternoon, half the array (option A: 26/2=13 panels) will be in shade and thus the entire system will not be producing power due to the roof angle ?, only until both roofs are in sunlight will the system (options 1-4 above) start producing power ? MLPE's Micro's and Optimizers are irrelevant to this scenario ? Only two strings with (optional two separate) inverters work ?

                no trees or other obstructions will cause shade on the upper most roof (2 story with attic) of my house today, that might not be true in the future as my neighbors tree's grow taller.

                Can't the system be configured with two strings in parallel for one inverter, thus allowing you to combine two arrays facing different directions. The Optimizers with help in case debris, crud or poop land on a panel.
                Last edited by JRqwertyui; 05-10-2017, 12:29 PM.

                Comment


                • #9
                  Originally posted by JRqwertyui View Post
                  Please let me make sure I understand, I'm still new to Solar. In the early morning and late afternoon, half the array (option A: 26/2=13 panels) will be in shade and the system will not be producing power due to the roof angle ?, only until both roofs are in sunlight will the system (options 1-4 above) start producing power ? MLPE's Micro's and Optimizers are irrelevant to this scenario ? Only two strings with (optional two separate) inverters work ?

                  no trees or other obstructions will cause shade on the upper most roof (2 story with attic) of my house today, that might not be true in the future as my neighbors tree's grow taller.

                  Can't the system be configured with two strings in parallel for one inverter, thus allowing you to combine two arrays facing different directions. The Optimizers with help in case debris, crud or poop land on a panel.
                  Read the book again. Such a system with those orientations, provided it's operating properly, will be producing power from sunrise to sunset, 365 days/yr., micros, string or optimizer equipped. An equally sized south facing array will, in all likelihood, produce more annual output per STC Watt, but you have the orientations you have. The goal is to maximize output for your orientations in safest, most cost effective way for the long term. String inverters with dual or multiple MPPT capabilities are one option as are multiple inverters or micros or optimizers.

                  Perhaps what might help me is for you to describe what you mean by "shade" - that is, do you mean partial shading as from trees or chimneys, etc. that only affects part of a portion of an array, or do you mean shading of an entire array or section, say east or west portions of an array, that are not exposed to any beam radiation because of the position of those arrays relative to the solar position - that is, the angle of incidence of beam irradiance is > 90 degrees ?

                  1.) A solar array, or some portion of that array that has all the panels in the same plane, and with that portion of the array uniformly illuminated, that is - no instantaneous partial shading of that array as for example, from a tree producing partial and variable shading, for part of or the entire, day as the sun moves across the sky and blocks the beam portion of solar insolation from reaching part of that array - will not benefit much, if at all, from using microinverters or optimizers.

                  2.) Most arrays are not ideally oriented. An example: An unobstructed array, say, one sitting in the desert on a flat plane located at, say, 35 deg. north latitude, with no vegetation around and having an array elevation of 45 deg. tilt, and at an azimuth of 90 deg. (that is facing east.) will be in shade (by virtue of having an angle of incidence for the beam portion of the irradiance >90 degrees) for at least part of the day - in the afternoon, with the sun illuminating the "backside" of the array. Such an array will still however benefit from some portion of solar insolation that is diffuse and coming from the entire sky dome and not solely from the direction of the sun. That portion, however, is usually and relatively small and of the order of ~ 5 -15+% or so of the total on sunny days, depending on a lot of things.

                  3.) However, because the shading for this example will effect the entire array, and not simply a portion of it, microinverters or optimizers will not result in more electricity production vs. a sting inverter.

                  4.) Microinverter's or optimizer's main advantage is when an array is partially shaded and or has time dependent shading on it as from trees, chimneys, adjacent buildings, etc. galloping across it over the course of a day. If the shading, or more correctly stated, actually having the direction of beam radiation is > 90 degrees, as would happen on afternoons for the above example, there is no usual advantage to micros or optimizers.

                  5.) An array will produce power when it is shaded, totally or partially. A rough 1st approx.: A partially shaded array with a string inverter w/out dual or multiple MPPT lwill produce power, and as a very rough 1st approx. only, something like the ratio of the amount of solar irradiance reaching the "most shaded" portion of an array to the part of the array that's unshaded. So, if "some" of the panels (maybe 30-50 % +/- some) are in "deep" shade, and seeing only, say, 20% or so of the unshaded intensity, the power production of the entire array will be closer to something like 20 % or maybe more of the unshaded output. Put another way, if a such a string inverter equipped array is 50 % shaded, its output will not be 50 % of an unshaded array - probably no where near it. That's one of the drawbacks of string inverters. As a sort of general statement, a string inverter equipped array's instantaneous (not necessarily daily) output is usually limited to something closer to the instantaneous output of the worst performing panel in that string or array. Micros and optimizers address a lot of that shortcoming.

                  6.) If you have east and west facing array portions, and those portions have no obstructions such as trees, chimneys or other things that will produce time varying shading on a daily basis on the arrays, equipping the arrays with micros or optimizers will probably not produce any more output. If you have such shading, micros or optimizers may produce more annual output.

                  7.) Once the sun gets past the plane of such (otherwise unshaded) arrays, that is, when the beam portion of the irradiance is > 90 degrees (As would be expected in the afternoon or in the morning at varying times depending on the time of the year), each array will be uniformly in shade or, better put, out of direct sunlight. Under those conditions, micros or optimizers won't produce much, if any extra output.

                  As I wrote, opinions vary, and while I'm not a huge fan of micros or optimizers, they have their place, and opinions vary. Just know how things work and why, walk in informed with your eyes open and question everything everyone tells you until you understand what they're saying.

                  Comment


                  • #10
                    Originally posted by JRqwertyui View Post
                    Please let me make sure I understand, I'm still new to Solar. In the early morning and late afternoon, half the array (option A: 26/2=13 panels) will be in shade and thus the entire system will not be producing power due to the roof angle ?, only until both roofs are in sunlight will the system (options 1-4 above) start producing power ? MLPE's Micro's and Optimizers are irrelevant to this scenario ? Only two strings with (optional two separate) inverters work ?

                    no trees or other obstructions will cause shade on the upper most roof (2 story with attic) of my house today, that might not be true in the future as my neighbors tree's grow taller.

                    Can't the system be configured with two strings in parallel for one inverter, thus allowing you to combine two arrays facing different directions. The Optimizers with help in case debris, crud or poop land on a panel.
                    If you have 2 unshaded equal length strings, all panels in a string having the same orientation, the strings
                    can be connected in parallel to a simple string inverter. With different orientations between the strings, the
                    peak power will be less than for an "all south" orientation. The reduced peak power will allow using a
                    somewhat smaller inverter and supporting plant. Micros will not allow this reduction.

                    If you get into some shade, optimizers will help, at increased complexity and cost. Do make sure the OC
                    voltage of your strings when cold doesn't exceed the max rating of the inverter. Here with temps dropping
                    to 27 degrees below zero F, I don't dare use strings of more than 12 panels, 720 total cells. good luck,
                    Bruce Roe

                    Comment


                    • #11
                      JPM: my shading would be (using your words) of an entire section of the array, either the east or west portions of an array, that are not exposed to any beam radiation because of the position of those arrays relative to the solar position - that is, the angle of incidence of beam irradiance is > 90 degrees due to the roof slope.
                      My vent air pipes and 2 X skylights should be below the racking height.

                      Still absorbing your and bcroe's replies... thank you, I'm sure I'll have more questions...
                      Last edited by JRqwertyui; 05-10-2017, 06:58 PM.

                      Comment


                      • #12
                        Originally posted by JRqwertyui View Post
                        JPM: my shading would be (using your words) of an entire section of the array, either the east or west portions of an array, that are not exposed to any beam radiation because of the position of those arrays relative to the solar position - that is, the angle of incidence of beam irradiance is > 90 degrees due to the roof slope.
                        My vent air pipes and 2 X skylights should be below the racking height.

                        Still absorbing your and bcroe's replies... thank you, I'm sure I'll have more questions...
                        Stay curious. Keep reading the book. If you're technically inclined a good undergraduate level text for solar position and angle geometry, and most everything else about solar energy for that matter: "Solar Engineering of Thermal Processes", Duiffie & Beckman.

                        Comment


                        • #13
                          Be aware that you are in CA and subject to 2014 Rapid Shutdown and you will find that most (not all) installers are mostly promoting microinverters or DC optimizers since it makes meeting the Rapid Shutdown requirements much easier from an installation point of view. There was a recent poll on the Mike Holt forums and it was overwhelming that installers are using module level electronics due to the 2014 RS requirements. Thus if you do find an installer that is quoting you traditional string inverter type setup for your rooftop just have a conversation with them about how they are going to comply with Rapid Shutdown. If they have a plan that meets code and deals with your shading then consider them as a viable option.

                          Comment


                          • #14
                            thank you tyab I'll ask about that....

                            so I have a new conundrum: if some of you have been following my bidding process I was going with:
                            30 LG 315N1C-G4 = 9450KW DC
                            SE7600A-US w/P320 Opts
                            Price: $28K ($2.96/w) pre-tax rebate

                            I stopped the entire process when I discovered the LG panels only have a 12y product warranty... so, I researched who offered 25y... ==> Pani and SPWR.
                            Unwilling to pay SPWR's premium, I contacted a local installer listed on the Pani website and landed up with yet another quote:
                            26 Panasonic VBHN330SA16 = 8600kw DC
                            w/SE7600-US P400 Opts
                            Price: $26,700 ($3.10/w) pre-tax rebate

                            crud, higher $/w... less total expense... Pani installer located in next town over (close by)... 26 vs. 30 panels = less penetrations, crud, what would you do ?
                            Someone mentioned the SE installer tool in anther post !!!! AWESOME tool...
                            Which leads to me second question: according to the SE tool, both systems annual MWh output is about the same.... I'm sure If a thought about why, i would come across the answer, yet the system with the higher KW DC label (LG) you would think, using same inverter (no clipping) would have the higher annual MWhs?. So, do I care about the $/watt, if the annual output is the same (according to the tool)...
                            Last edited by JRqwertyui; 06-22-2017, 03:48 AM.

                            Comment


                            • #15
                              Originally posted by JRqwertyui View Post
                              thank you tyab I'll ask about that....

                              so I have a new conundrum: if some of you have been following my bidding process I was going with:
                              30 LG 315N1C-G4 = 9450KW DC
                              SE7600A-US w/P320 Opts
                              Price: $28K ($2.96/w) pre-tax rebate

                              I stopped the entire process when I discovered the LG panels only have a 12y product warranty... so, I researched who offered 25y... ==> Pani and SPWR.
                              Unwilling to pay SPWR's premium, I contacted a local installer listed on the Pani website and landed up with yet another quote:
                              26 Panasonic VBHN330SA16 = 8600kw DC
                              w/SE7600-US P400 Opts
                              Price: $26,700 ($3.10/w) pre-tax rebate

                              crud, higher $/w... less total expense... Pani installer located in next town over (close by)... 26 vs. 30 panels = less penetrations, crud, what would you do ?
                              Someone mentioned the SE installer tool in anther post !!!! AWESOME tool...
                              Which leads to me second question: according to the SE tool, both systems annual MWh output is about the same.... I'm sure If a thought about why, i would come across the answer, yet the system with the higher KW DC panel (LG) you would think, using same inverter (no clipping) would be higher annual MWhs?. So, do I care about the $/watt, if the annual output is the same (according to the tool)...
                              It is a hard swallow for me to believe a system that's 10 % smaller in the same location, orientation and duty will produce about the same annual output. That's contrary to most everything I've learned, measured and observed. But don't believe me or PVWatts or any other model, although they're believed to produce reasonable results when using reasonable inputs that reflect actual conditions. Check PVOutlet for your area, or any area for that matter, and compare actual output per kW reported for actual installed systems in similar orientations and see how many differ by 10 %. A few % maybe, but 10 % is a tough sell to my experience.

                              On these warranty knots you seem to want to tie yourself into: Do/think as you please, and NOMB, but the best warranty you can get is the one you give yourself by understanding what you're buying and being your own project/Q.C. manager, and not assuming a vendor will do it right without some involvement from you. Look, one or more of the following will probably happen before 10 years: 1.) You'll move, 2.) Your array will be working but obsolete and you'll want something newer/better/cheaper, 3.) The energy picture will be different and solar will have become irrelevant. FWIW, the POCO's will probably see to it.

                              Also, read the warranty - then read it again, and think like a vendor when you read. Most warranty (or performance) claims never get honored. They're pretty bulletproof in the vendor/mfg's favor. You're worried about something that has a small probability of happening and a smaller probability of getting paid.

                              Warranties are somewhat important, but with panels looking good for the long run and infant mortality being the main cause when the (so far) few failures do occur, putting a deal at risk for warranty differences when there is so much other, and much more important things - like vendor quality, and roof integrity for starters to consider seems misplaced priorities to me.

                              Overall, $3.10/Watt isn't that far from $2.96/Watt in the bigger scheme of things. If I was you, I'd stop the fool's errand of chasing low initial cost and start looking for the most long term value and long term bang for the buck. The two are not the same. Terrible to pay too much - Worse to pay too little. Buy cheap, buy twice. A few pennies/Watt is peanuts in the bigger scheme of things. You'll probably pay more long term than that in cost ineffectiveness by chasing a 100 % bill offset and not know why.

                              Enough of the Dutch uncle. I said my peace.

                              On the issue of price /Watt vs. price per kWh of production, if the annual output per installed STC Watt for quality systems is about the same, +/- a few %, then $$/installed STC Watt is a valid figure of merit.

                              Take what you want of the above. Scrap the rest.
                              Last edited by J.P.M.; 06-22-2017, 04:07 AM.

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