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  • North facing Panels

    Had a system installed with two inverters and 42 panels. Some were placed on south roof and some were placed on the North roof. The system is rated 11 KW D.C. with two inverters.

    I live in Southern California and currently the 23 Southern roof panels in full sun without clouds generate around 3700 watts during peak hours . It has a 6 KW inverter.

    The North Roof is generating about 800 watts with 19 panels (265) under same circumstances.

    I'm wondering what to expect with the North Roof around Summer Soltice? I'm guessing that the north roof will give me only around 3 KW maximum during summer soltice.

    Neither exposure has any shade issues to speak of.

    Would a West exposure generate more energy then the north exposure (again no shade issues )? I just didn't have enough roof space to fit all the panels on the South roof.

    I have not made the final payment on this system. Should I request (demand) that the north panels be moved to the west exposure ?

    I did question the installer about the northern exposure before the panels were installed and he told me that's what his engineer told him to use. Now that I've studied the issue more I'm thinking, although I'm no expert, that perhaps I made a mistake allowing the north panels to be installed ?




  • #2
    PVWatts will give you an estimate of the different scenarios for comparison. Link is available on the forum home page.

    WWW

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    • #3
      Panels on the North roof are all but useless. It's the worst direction possible in the northern hemisphere. West facing would be far better.
      Did you use one of the big name companies (SolarCity, SunRun, etc)? They seem to put panels everywhere, regardless of how much power they produce. More panels means more money.

      I would never have let them put them on the North roof.

      Comment


      • #4
        North facing or northerly oriented panels in the northern hemisphere are almost always the least productive orientation.

        As WWW writes, check out PVWatts for an estimate of relative output vs. orientation. Summer will be more productive, but I you're on net metering, in economic terms annual output is what counts .

        While I believe PPA's are fraught with drawbacks, and this is definitely not an endorsement of such schemes, if the deal is to only pay for what is produced as most PPA's are structured, such arrangements may take some of the dumbness out of a PPA, but only if the price is low enough with no annual escalation.

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        • #5
          Originally posted by compchat View Post
          Had a system installed with two inverters and 42 panels. Some were placed on south roof and some were placed on the North roof. The system is rated 11 KW D.C. with two inverters.

          I live in Southern California and currently the 23 Southern roof panels in full sun without clouds generate around 3700 watts during peak hours . It has a 6 KW inverter.

          The North Roof is generating about 800 watts with 19 panels (265) under same circumstances.

          I'm wondering what to expect with the North Roof around Summer Soltice? I'm guessing that the north roof will give me only around 3 KW maximum during summer soltice.

          Neither exposure has any shade issues to speak of.

          Would a West exposure generate more energy then the north exposure (again no shade issues )? I just didn't have enough roof space to fit all the panels on the South roof.

          I have not made the final payment on this system. Should I request (demand) that the north panels be moved to the west exposure ?

          I did question the installer about the northern exposure before the panels were installed and he told me that's what his engineer told him to use. Now that I've studied the issue more I'm thinking, although I'm no expert, that perhaps I made a mistake allowing the north panels to be installed ?


          Unless those North panels have been tilted up to "face" the South then they will never produce anything close to their nameplate rating.

          Moving them to the West facing side of the house would be the action I would take.

          Comment


          • #6
            Originally posted by compchat View Post
            Would a West exposure generate more energy then the north exposure (again no shade issues )?
            Yes. Near the coast west is generally better than east due to June gloom (clouds in the morning in the summer, usually burn off around noon.)
            I did question the installer about the northern exposure before the panels were installed and he told me that's what his engineer told him to use.
            Perhaps he needs a new engineer.

            Comment


            • #7
              Ditto on Emartin00
              BSEE, R11, NABCEP, Chevy BoltEV, >1800kW installed

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              • #8
                One more time: Check PVWatts estimates for different orientations for your location.

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                • #9
                  I think the best time to raise the red flag is when comparing dollars per watt before signing the contract. That would have caught the unproductive north-facing panels.

                  What brand & model panels, and how much are you paying (without subsidies)?

                  Can you post pictures?

                  I'm using reverse-tilt mounts for a couple panels on the north side of my house so they face the sun better, but I can't swear that it's a good idea.

                  Comment


                  • #10
                    To perhaps clear up one point: It is not necessarily the orientation of what the panels sit on, it's the orientation of the panels themselves.

                    Often and commonly, solar arrays are parallel to the roof they sit on. That's probably best for a lot of reasons. But, because that's the usual and common arrangement, does not mean other support arrangements are not possible.

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                    • #11
                      Originally posted by DanKegel View Post
                      I think the best time to raise the red flag is when comparing dollars per watt before signing the contract. That would have caught the unproductive north-facing panels.

                      What brand & model panels, and how much are you paying (without subsidies)?

                      Can you post pictures?

                      I'm using reverse-tilt mounts for a couple panels on the north side of my house so they face the sun better, but I can't swear that it's a good idea.
                      While I am working on ROI analysis, I do believe that $/W is one part of the story. I have limited space on my roof on SW and SE. The most open space is NW. I got quotes from several companies. In some cases, they recommended a higher nameplate wattage panel and $/W is higher. I took advice from JPM and other members and started using PVWatts and SAM.

                      The ROI on the system w/ higher $ per DC Watts is better than the one with lower $ per DC Watts for same total system output. The reason being, I can fit 12 panels on SW & SE. With higher output panels, I just need to use SE & SW panels. On lower wattage panels, additional panels go NE. Performance of NE facing panels (one of major brand-name company wants to put 6 panels there) is pretty bad.

                      Just my 2 watts

                      Comment


                      • #12
                        Originally posted by VGdublin View Post

                        While I am working on ROI analysis, I do believe that $/W is one part of the story. I have limited space on my roof on SW and SE. The most open space is NW. I got quotes from several companies. In some cases, they recommended a higher nameplate wattage panel and $/W is higher. I took advice from JPM and other members and started using PVWatts and SAM.

                        The ROI on the system w/ higher $ per DC Watts is better than the one with lower $ per DC Watts for same total system output. The reason being, I can fit 12 panels on SW & SE. With higher output panels, I just need to use SE & SW panels. On lower wattage panels, additional panels go NE. Performance of NE facing panels (one of major brand-name company wants to put 6 panels there) is pretty bad.

                        Just my 2 watts
                        And you're having fun I bet.

                        What you're finding is certainly possible, but I'd also look at LOCE's for all orientations. Different orientations of the same array size will indeed produce different ROI's with the optimum orientation usually producing the greatest simple ROI and the lowest LOCE.

                        Commonly with tiered rates, but not always, and separate from % total offset, a smaller array will be more cost effective per nameplate Watt than a larger array in the same orientation and duty. So, fewer panels in one orientation due to space constraints may be more cost effective due to smaller size, mostly but not entirely separate from orientation, even if a different orientation with a larger size produces more annual output per nameplate Watt. It can get tricky.
                        A larger possible area for a bigger array facing away from the equator as your NW orientation for example, will have at least two strikes against it vs. a smaller equator facing array: Less resource availability/area, and perhaps replacing more of the lower tier electricity to some degree, depending on how much power is offset.

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                        • #13
                          This simply proves that the grid tie solar world is full of crooks. The government should be basing any tax credits on net metering, not the wattage of the panels. Seeing pics of panels on north facing roofs, panels in shade and even one system where panels were installed in shade made by an adjacent house all add up to this conclusion.

                          Comment


                          • #14
                            Originally posted by TurkeyBob View Post
                            This simply proves that the grid tie solar world is full of crooks. The government should be basing any tax credits on net metering, not the wattage of the panels. Seeing pics of panels on north facing roofs, panels in shade and even one system where panels were installed in shade made by an adjacent house all add up to this conclusion.
                            State subsidies tend to have an efficiency condition in their terms that would disallow subsidy for North facing panels unless the installer lied when filling out the forms.
                            SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                            • #15
                              I have often wondered why the federal solar tax credit is 30% without regard to efficiency. A production tax credit wouldn't have the problem you describe, but for some reason that's used more for wind than for solar. (And PTCs can also have perverse effects, like how wind farms are incentivized to produce even when the price for power goes negative.)

                              This underscores how tricky regulation is to get right. A carbon fee & dividend would be much simpler, and wouldn't suffer from either of those problems.

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