Announcement

Collapse
No announcement yet.

SolarEdge inverter sizing

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • SolarEdge inverter sizing

    I'm planning on installing a 8.53kW system using SolarEdge's power optimizers and inverter.
    SolarEdge's tool suggests going with their 7.6kW inverter.
    That results in "DC/AC sizing: 112.17%"

    I'll have ~20% of the panels facing roughly West, and ~30% facing roughly East (but both relatively shallow - 4/12 roof)
    And the rest facing south.

    Obviously I'm concerned about undersizing the inverter and not making full use of the panels.
    But maybe with the different orientations I won't hit that max power anyhow, so I should just go with the 7.6kW.

  • #2
    Originally posted by foo1bar View Post
    But maybe with the different orientations I won't hit that max power anyhow, so I should just go with the 7.6kW.
    Bingo!

    1. The panels are not likely to produce their STC rated power even at noon unless the weather is cold but clear.
    2. The peak hours for the two array orientations are different enough that the overlap for clipping, especially considering 1, are not going to overlap enough to hurt your power output. At least not enough to justify a larger inverter.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

    Comment


    • #3
      There's another thread about this just a few rows down the page.

      FWIW I agree with your choice.
      6k LG 300, 16S, 2E, 2W, Solaredge P400s and SE5000

      Comment


      • #4
        Is there a down side to going with a bigger inverter? The SolarEdge sizing tool also showed I should go with the SE10000US 10.0kW inverter instead of the bigger SE11400US 11.4kW inverter but the price difference is less than $100 and I figure I'd like to go bigger in case I want to add panels later, which shouldn't be terribly difficult with the solar optimizer setup.

        Comment


        • #5
          Originally posted by HX_Guy View Post
          Is there a down side to going with a bigger inverter? The SolarEdge sizing tool also showed I should go with the SE10000US 10.0kW inverter instead of the bigger SE11400US 11.4kW inverter but the price difference is less than $100 and I figure I'd like to go bigger in case I want to add panels later, which shouldn't be terribly difficult with the solar optimizer setup.
          Those of the oversizing school of thought say the inverter is more efficient the closer it is to maximum output. Thus with a larger inverter, you would get less power in the mornings and evenings.

          2 installers and Solaredge themselves have told me this.

          But in the end I'm just repeating what I hear.
          6k LG 300, 16S, 2E, 2W, Solaredge P400s and SE5000

          Comment


          • #6
            Originally posted by Bikerscum View Post
            Those of the oversizing school of thought say the inverter is more efficient the closer it is to maximum output. Thus with a larger inverter, you would get less power in the mornings and evenings.
            2 installers and Solaredge themselves have told me this.
            But in the end I'm just repeating what I hear.
            Lets see some HARD NUMBERS backing those claims. Until they are presented, and actual
            calculations done, I think it is way too insignificant a point to even consider. My Fronius
            actually contains multiple units, so it can switch to the most efficient mode for the power
            available. Bruce Roe

            Comment


            • #7
              Originally posted by bcroe View Post
              Lets see some HARD NUMBERS backing those claims. Until they are presented, and actual
              calculations done, I think it is way too insignificant a point to even consider. My Fronius
              actually contains multiple units, so it can switch to the most efficient mode for the power
              available. Bruce Roe
              No hard numbers. All I can say is Solaredge wants to sell you a smaller, cheaper (and I would assume less profitable) inverter than you might otherwise choose. I just can't see any agenda there.

              Question tho.... why does your Fronius bother with the multiple units if the amount to gain is insignificant?

              But again, I know less that the guy asking the question in the first place.
              6k LG 300, 16S, 2E, 2W, Solaredge P400s and SE5000

              Comment


              • #8
                Originally posted by Bikerscum
                No hard numbers. All I can say is Solaredge wants to sell you a smaller, cheaper (and I would assume less profitable) inverter than you might otherwise choose. I just can't see any agenda there.

                Question tho.... why does your Fronius bother with the multiple units if the amount to gain is insignificant?
                Good question. The previous discussion was if there was much power conserved using
                perhaps a 6KW inverter to put out 6KW, versus using a 7KW inverter to put out 6KW.

                But this question relates to when say, the same panels drop to 1 KW. Again there won't be
                much difference in power loss between the 6KW and 7KW inverter. But lets say the 7KW
                Fronius actually contains 2.5KW and 4.5KW inverters which are switched in. Using the
                2.5KW section to handle 1KW will definitely have an edge over either the 6KW or the 7KW.
                That edge is gained without any trade offs against occasional clipping. Bruce Roe

                Comment


                • #9
                  Here is some testing I ran across a while back when I had to make the decision. I THINK it shows slight undersizing of the inverter (oversizing of the system as they call it) is a good thing.

                  Inverter performance
                  6k LG 300, 16S, 2E, 2W, Solaredge P400s and SE5000

                  Comment


                  • #10
                    Originally posted by bcroe View Post
                    Lets see some HARD NUMBERS backing those claims. Until they are presented, and actual
                    calculations done, I think it is way too insignificant a point to even consider. My Fronius
                    actually contains multiple units, so it can switch to the most efficient mode for the power
                    available. Bruce Roe
                    I do believe undersizing inverter does yield higher output.

                    I added 2 additional panels to my solar array and I did get higher ouput from the same sysem (more by %). The panels addition were done on 5/29/2014 and here are the specifcaition and result:

                    The original system were Bosch 255W X 26 @ 6.63kW with SMA 6000-TL-US-12 inverter in 2 X 13 panels arrays. The 2 additional panels were Bosch 245W (not 255W panels) I added 1 panel to each array. The update solar system will be 7.12kW.

                    Before 5/29/2014, the best daily output were 42.36kWh. After panels additional, the result were 47.66kWh on 6/03/2014. The reason I did not included the immediate result is: my inverter fail right after panels addition and my installer replace the inverter on 6/02/2014. 06/03/2014 was the first day I have the complete whole day output. Here is the calculation:

                    Before: 42.36 kWh / 6.63kW = 6.3891
                    After: 47.66 kWh / 7.12kW = 6.6938

                    From 6.63kW to 7.12kW is: 7.39% increase in system size.

                    From 42.36kWh to 47.66kWh is: 12.51% increase in system output.

                    I do realized that system does wake up little ealier and rest little later than before. Again, this is my finding without any actual measurment on weather,temp....etc. With the mismatching panels addition, I should be getting lower % increase comparing with size vs output, but in this case I do get higher output.

                    Comment


                    • #11
                      Originally posted by silversaver View Post
                      [B]I do believe undersizing inverter does yield higher output. [/B
                      Before: 42.36 kWh / 6.63kW = 6.3891
                      After: 47.66 kWh / 7.12kW = 6.6938
                      From 6.63kW to 7.12kW is: 7.39% increase in system size.

                      From 42.36kWh to 47.66kWh is: 12.51% increase in system output.
                      Thanks for the input. Now I will be forced to come up with the method I would
                      like to use for a comparison; will have to be a little later. Bruce Roe

                      Comment


                      • #12
                        Newb question, if hooking up too much solar and the perfect cold, bright day occurs, is that a bad thing? 10kW in on a 7.6kW SolarEdge?

                        Comment


                        • #13
                          for the odd times that happens it should be fine, cool weather, the inverter will limit itself to nameplate power or thermal limits.
                          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

                          Working...
                          X