Solar Panels On Roofs Facing Different Directions? Then You Need To Do This.

Here is a photo I took of a house around the corner from me.

A House With Solar Panels Facing Different Directions

As you can see, it has solar panels on 2 separate roof areas. In solar jargon, you would say there are 2 “strings” of solar panels.

The main string is facing North, which is the best roof orientation for solar panels. These panels should get the optimum amount of sun throughout the day.

The smaller string is facing East. These panels will get 15-20% less sunlight than the panels facing North.

Obviously the installer could not fit all the panels on the North facing roof. Fair enough.

If your home will require solar panels on multiple roof areas, which face different directions, then you should use a special type of inverter to ensure that you still get good system performance.

Multiple Roof Areas Require Multi String Inverters

If you have solar panels facing different directions then you need a Multi String Inverter (also called a Multi MPPT inverter) with one string/MPPT for each roof area.

In order to maximise output from your solar panels, each roof area’s panels must be connected to a separate inverter string that has its own Maximum Power Point Tracker (MPPT). The MPPT is a bit of electronics that optimises the power from the panels. It is impossible for an single MPPT to work optimally if it is connected to panels which are facing different directions.

[ For the technically minded people the reason for this is that the IV Curves are different for each roof area because they get a different amount of irradiance from each string of panels. This means there are 2 maximum power points to choose from and an MPPT can only optimise properly to 1 maximum. ]

Caveat: The exception to this rule is if you have 2 identical strings, 1 facing east and 1 facing west.

If you are using a reputable solar company then they will employ a CEC accredited solar designer to individually design each homes solar system, and take stuff like this into account. If you ask to see the design drawing of your solar system they should show you it. For the solar system above, it would look something like the sketch below – notice how it clearly shows each string is wired into its own MPPT in the inverter.

A diagram showing 2 separate strings of solar panels wired into 2 separate MPPTs in the solar inverter.

If your system is not designed like this then the string of solar panels with the least sun shining on it at any one time will drag the other panels’ power down to its low power output. This will reduce your power output. If your solar installer cannot provide a diagram like this as part of your quotation (and more importantly as part of your final contract when you are ready to buy) then move quickly on to a more professional firm.

 UPDATE: June 2013

Thanks to Martin in the comments below for pointing out that, since I wrote this post, an alternative option has come to the market in Australia: micro inverters. Micro inverters are a fantastic new technology whereby each panel is has its own inverter, and there is no central inverter at all. This means that every panel is optimised independently and you can have as many roof areas pointing in as many directions as you want. You can read lots more about the pros and cons of microinverters here. I’m a fan – I have 6kW of the little beauties on my roof in sunny Radelaide.

UPDATE: March 2016

Thanks to Hagen for pointing out that using the phrase “This will cripple your power output” is an exaggeration, so I changed it to “This will reduce your power output” . In the example in the line diagram, due to the configuration of the strings the power output will be reduced slightly, with a single MPPT, not crippled. In other configurations the power reduction could be much more. A good solar installer will quantify all this for you as part of the design documentation.

About Finn Peacock

I'm a Chartered Electrical Engineer, Solar and Energy Efficiency nut, dad, and founder of SolarQuotes.com.au. My last "real job" was working for the CSIRO in their renewable energy division.

Comments

  1. Juliusz Sciezyna says

    HI,

    I found your site exceptionally informative in regard to solar power. Thank you for your effort and time to put the info here.

  2. Hi Flinn
    Looking at purchasing a 3kw SMA sunny boy inverter and using 250watt bosch panels x 12.
    What are your thoughts? Am i making the right decision.
    The company is Aus 1 solar. Has anyone used this company??

    • HI Finn,
      I’ve got a 2kw system on max. rebate due to run out in Jan. 2020.
      I have 18 panels totalling about 3.6kws supporting it on a single string East/West configuration.I reckon I can accommodate another 20 panels, – and if they were all say 250’s, thats about 9.5 kw – 8 of those new panels would be North facing, with 2 East, 2 west and 8 south, so I would guess we could capture up to about 6kw an hour on a good day.
      Should I upgrade now or wait till the big subsidy expires?

      • Ronald Brakels says

        Hello Jenny, Ronald here.

        3.6 kilowatts is a large system to have on a high feed-in tariff. Economically I’m certain you’d be far better off waiting for your high feed-in tariff to expire. If you are motivated by environmental concerns you could get a large system installed now would reduce emissions, but you could do the same by helping a relative or charity get solar.

      • Hi,Finn

        I have a similar setup in mind ,10 North , 2 east, 2 West then 10 South . Question, How many strings would this setup require and would it be better to use microinverters? 3 Phase
        Current setup is 8 facing North single inverter 2 KW single Phase on three Phase home supply.

        • Ronald Brakels says

          Hello Trevor, Ronald here.

          The 10 north and 10 south facing panels could be attached to one string inverter with the north facing panels on one inverter MPPT (Multiple Power Point Tracker) and the south facing panels on the other inverter MPPT. Technically, I suppose it would be possible to put the remain 2 east and 2 west facing panels on a small single MPPT inverter. But rather than pay for those 4 panels and a second inverter you would probably be better off skipping them and using the money you save to buy higher capacity north and potentially south facing panels. If you decide you want to have the east and west facing panels then putting them on microinverters isn’t a bad option as they will perform slightly better and the cost for just 4 panels can compare well to the cost of a 4 panel string inverter installation.

  3. Hi Flinn
    Looking at purchasing a 3kw SMA sunny boy inverter and using 250watt bosch panels x 12.
    What are your thoughts? Am i making the right decision.
    The company is Aus 1 solar. Has anyone used this company??
    Flinn the panels are c-si M60 Eu 30117
    The inverter is sunnyboy 3000TL

  4. Hi all, I have just been offered a 4.5KW system using LG panels and a sunny 5000 inverter for $8207 from aus1solar.. the old saying of it sounds too good to be true is ringing in my ears, but the price is too good to completely ignore!

    Does anyone have info on aus1solar?>??

    Please help!!

    Thanks,

    Luke

    • My work collegue is having some difficulties getting AUS1SOLAR to complete the work (5Kw Bosch system) at her house. Apparently everything is installed (29 Dec 2012) but not yet working (9 Jan 2013).
      Luckily she has not fully paid them yet. They keep ringing her asking for the remaining money but she refuses to pay until they complete the work.
      Good prices and good equipment yes but do not pay until fully installed and working.
      You have been warned.

    • Jack Wallace says

      Hi Luke.
      ???..”the price is too good to completely ignore”
      I’ve never been one who pays over the odds for ‘brand-names’.

      There’re plenty of good, reliable components around at a price which would allow an installation for about $1 per watt.

  5. Hi Finn
    We are in process of designing and building our own house. We have plenty of north facing roof but there is one section which the roof has angle of about 10degree and its away from the rest of roof bulk.
    We would like to allow for at least 10-12 panels on it.
    Do we still need 2 inverters or can all areas use same inverter as they are all facing north. Is the distance of inverter to panels a factor that needs to be considered?
    Thanks in advance.

    • If the 2nd roof area is a very different pitch to the 1st roof area then to get maximum energy from the arrays you need either:

      2 inverters or
      an inverter with 2 MPPTs or
      you need to adjust the shallower pitch to match the steeper pitch.

      If it is less than 10 degrees difference then get your installer to calculate the power hit you’ll take from not doing the above and decide if it is worth the extra cost.

  6. Margaret Clay says

    Hi Finn
    I am really glad I found your website. Having started looking at where we and how we can site solar panels, I am able to weigh into the duscussions with the solar company and ensure that I am happy with the final result. Your site is soooo informative and very interesting. I am now happy to proceed with installations knowing I have had a base check on what is being proposed. Thanks Again

  7. Check out micro inverters a new thing. All round even better. enphase, power-one Aurora micro inverters etc. Have a google.

    • Hi Martins,

      Great point! I’ve updated the post to add the microinverter option.

      Finn

      • Dear Finn,

        thank you for all your hard work to benefit all of us.

        Martins

      • We will be installing east and north facing panels on a 2 story home. The north facing panels are all on the upper story with no overshadowing concerns. The east facing panels are on 2 roof spaces ( upper and lower floors) and will consequently shade at different times.
        Looking to put TIGO optimisers on both of the east facing sets of panels. The northern panels would not be optimised.
        Would this work ok? Do we need multiple arrays for the inverter?

        • If you are not going to put Tigos on all the panels facing both North and East, then you really need to use an inverter with 2 MPPTs. There are lots of inverter options and they cost no more than single MPPT inverters, so this should not be a problem.

          If you only have Tigos on the East facing panels then, in the morning the north facing panels will get less sun than the east facing panels and drag the whole array down. It would also violate the Australian Standard AS5033 from my understanding of it.

  8. Mark Evans says

    Interesting. Does this apply to a yacht where the 2 panels are almost horizontal but one is angled 5% left and the other 5% right? What sort of 12v regulator is required when you have several banks of panels pointing different directions? Thanks.

  9. Wayne Ferg says

    I have 16 solar panels in a 3.04 Kw solar array, with a 5 Kw inverter. The most the readout has ever read is 2.6Kw. I have room to add 2 more panels. can they just be attached and is it simple to do. What do I need to watch out for. is it economic to source secondhand panels.

  10. The generalization in the article makes it incorrect. With identical strings, single-MPPT inverters can handle strings with different orientations. The Fronius research findings to that effect were referenced on Whirlpool.

  11. Hi there,

    I can only have panels installed on roofs facing east or west. I intend to have a 5kw one. With this roof orientation, is it worth the expense? Should it be all panels on the East side or the West side? Or is it best to have it split on both roofs?
    Thank you.
    Denise

  12. Tim Chirgwin says

    Hi Fynn,
    With off grid home would North west be the better to still keep worst month power to charge batteries. Or still best to stay North as the worst in June has the sun over the horizon before as we get home to cook tea anyway. The summers and long days we have ample power anyway.

    • Hi Tim,

      Yes – the more you face west the more power you will get late in the day.

      The best way to optimise your system for winter production though is to use a steeper panel angle.

      Winter optimised angles for solar (degrees from horizontal):

      NSW: 50 deg
      QLD: 44 deg
      SA: 51 deg
      VIC: 54 deg
      WA: 48 deg

      Hope That Helps,

      Finn

  13. Hi Finn

    I´m designing a PV system in Brazil and my current scenario is:

    I have a roof facing northeast that fits 5 modules and another roof facing northwest that fits 6 modules. Currently in Brazil, there is no certified micro inverters and that prevents me to use them.

    I am researching for a dual mppt inverter, to connect two string 1 with 5 modules in series and another with 6 modules series. The point here is that I am afraid that will not have the necessary DC voltage for the input on most of the inverters.

    Do you have any suggestion in this case? If I connect all the 11 modules in series and connect to the inverter, my generation will be highly impacted?

    thanks,
    Marcos

    • G’day Marcos,
      Five panels connected in series will produce on average ca 150V. The minimal input voltage for an inverter is usually around 80V. So, a dual-MPPT inverter will be able to handle your panel strings.
      Cheers,
      Josip

  14. John Henshaw says

    I have been exploring the possibility of splitting our 18 NE-facing array to achieve better generation numbers and Fronius confirmed our Conergy WR 3300 which is now 6+ years old via this interesting link they sent me: http://www.energymatters.com.au/images/news/2013/east-west-solar-paper.pdf

    On this basis it would seem there’s no great problem with a single MPPT inverter such as ours.

  15. Tom Anderson says

    Hi Finn,

    I’ve just ordered a system using 14x 290W panels and a Fronius Primo 3.5kW inverter. The installers have just been here but sadly had to cancel due to wet weather, however they were able to do some measurements to determine panel placement and found that they can only fit 13 panels on my main north-facing roof. Splitting the strings between multiple north aspects will mean they end up with cabling that’s too long. They’ve recommended a North/West split.

    I’m wondering if you could provide some guidance on my options and what would be better.

    I live in the Bundaberg area. My north facing roof is not quite north (approx. 10 degrees), the west facing roof is approx 280 degrees. They’ve suggested 8x panels on the north face and 6x on the west face.

    I work from home – running a small aircon most days along with a few computer monitors, laptop etc. I want to run as much as I can off the power I’m generating during the day so will schedule dishwashers, washing, charging of devices etc etc. There are only two of us living in the house.

    Would I receive more benefit from dropping one panel and having 13x north facing, or stick with the 14x panels split as detailed above? How would the peak power generation look with the split configuration – am I likely to see a longer peak? Is the inverter still sized appropriately for this sort of configuration?

    • Ronald Brakels says

      Hello Tom. Ronald here. You can use PVwatts to get an approximate value for how much a rooftop system will generate:

      http://pvwatts.nrel.gov/

      The closest location it has information for is Gladstone, but conditions are similar enough to make a reasonable comparison.

      According to PVwatts 13 panels, which comes to 3.77 kilowatts, at 10 degrees orientation will produce 6,308 kilowatt-hours over a year.

      Eight panels, or 2.32 kilowatts, facing north at 10 degrees will produce 3,882 kilowatt hours while 6 panels, or 1.74 kilowatts, facing west at 280 degrees will produce 2,569 kilowatt-hours. This comes to a total of 6,451 kilowatt-hours.

      So according to PVwatts you can expect to produce around 2% more electricity with 8 panels facing north and 6 facing west than with 13 north. In addition, their production will be slightly lower at noon and slightly higher later in the afternoon which will improve self consumption and help provide power for afternoon air conditioning.

      While conditions in Gladstone will be a little different from Bundaberg, it seems very likely you’ll be better off with one extra panel and having them face two directions.

      • Tom Anderson says

        Thanks Ronald. Is my inverter still sized appropriately for a split orientation?

        • Ronald Brakels says

          The 3.5 kilowatt inverter can have up to 4.66 kilowatts of panels put on it and as 14 panels is only 4.06 kilowatts you are fine. You could even add two more panels and still be within the limit. (You may want to ask the installer if that’s possible.) The inverter can handle two strings or sets of panels, with each string facing a different direction, so that’s not a problem.

          • Tom Anderson says

            Thank you!

          • Great thread. I’m new to solar and further to above want some general guidance on the benefit of splitting an array on both the north and west facade.

            I have a new house, and space for panels on the north side of my roof but also could squeeze some on to the western side. Common sense tells me that if I use micro inverters or multiphase inverter then splitting the system would allow me generate more energy over a longer period. I live in western sydney and get western sun until about 7-8pm in summer. I hardly ever see panels split like this. Is there a reason?

            Ps. I’m waiting on quotes And will run this by the installers but wanted a bit of prelim advice.

            Thanks

          • Ronald Brakels says

            Hello Shaun

            It is definitely possible to have two arrays of solar panels on your roof, one facing north and one facing west. In Sydney west facing panels will produce an average of about 15% fewer kilowatt-hours than north facing panels. You can use microinverters but all except the smallest string inverters (the most common type of solar inverter) have two MPPTs (Multilple Power Point Trackers) that allow two independent arrays to be attached. Note with string inverters it is possible for there to be limits on how different the two arrays are in size.

            Using optimizers or panels with panel string optimization can also allow panels to be placed facing different directions.

  16. Hi,

    I am planing to install a 2kw solar panel and every solar company has told me that my roof is too small and cannot fit in the solar panels. What is an alternative to get solar panel

    • Ronald Brakels says

      Hello Ash

      You must have an extremely small roof if you can’t fit a 2 kilowatt system on. Or maybe the problem is your roof is both small and difficult to install on. Usually, if a roof is difficult to install on the problems can be worked around by using panels with microinverters, DC optimizers, or by using panels that have panel string optimization, as these allow panels to be placed facing in a variety of different directions.

      But assuming there is no room on your roof for panels, it is possible to place them on racks on the ground. But this will require unshaded ground space and you may require permission from your council.

      If you are looking for other ways to save energy you can look into insulation, LED lighting, energy efficient appliances, and so on.

  17. I have been offered 24 x 270 watt panels with a 6.5kw with Aussie Solar, I live in the south of the Gold Coast QLD, But i was told from another company who also quoted me said in my area we are only allowed 5.5kw due to single phase power . We have a domestic home.

    • Ronald Brakels says

      Hello Ann

      On the main grid in Queensland households with single phase power can install up to 6.66 kilowatts of solar panels. Unless you are in a very rural area for the Gold Coast you should be on the main grid.

  18. Love the information in this article but one question I have that’s not covered with a single or multiple string is does the number of panels matter. Ie do strings need to have equal or even planels, such as 2, 4, 6 or 8 or can they be any combination as long as the total output is under the inverters capacity?

    • Ronald Brakels says

      When an inverter has two MPPTs the two separate arrays of panels can have different capacities. But inverters can have restrictions on how different the arrays can be and even restrictions on how how different their orientation can be, so that is something to watch out for. Total panel capacity can be one third more than the inverter capacity.

  19. Hi,

    A solar company offer me solar system with three different direction, east (6panels) +north (6panels) and west (6panels) with ABB inverter.

    Is it possible to install a solar system with 3 different direciton?

    Thank you.

  20. Hi Finn,

    I realise this question is specific to my own needs but if you can give me answer I will appreciate it.

    I have high voltage panels that mean they run at about 59. My 600KW inverter has failed and I am being told that the only way to be safe for a replacement is to split my 10 panels into two strings and install a multi string inverter. The technical guy told me he would take two panels off the roof and run a cable through to do the job. It occurs to me that this could be problem in as much as how does one easily make the first cable stop at teh 5th panel and likewise the second cable do the same when my 10 panles are firmly fixed to the roof?

    • Ronald Brakels says

      Hi Mike, Ronald here.

      I don’t know how your panels are currently arranged, but in order to make the single string you have now into two separate strings, whoever is working on them will need to unplug the connectors between the two middle panels so there will be 5 panels on one side and 5 on the other. Lengths of cable will be attached to those detached connectors and run down to the new inverter. This will make two separate loops of cable or strings, each with 5 panels. Two panels will be temporarily removed for access. There’s no real chance of getting the wrong number of panels on a string unless the person doing the job can’t count to five.

      • Many thanks Ronald, you have put my mind at rest. I will take this up with my installer when comes along in a few day’s time

  21. Hi Finn/Ronald,

    My solar contractor has proposed a north and west facing system for me, 10 panels north and 7 west, Trina Honey M 305w panels on a 5kW Fronius. We use quite a bit of power in the afternoon to early evening so the intention is to have reasonable capacity on the West especially in summer. The contractor recommended that a minimum of 7 panels needed to be on the west string to ensure the inverter ran to capacity. I would have preferred an 11/6 or 12/5 split to maximise northern generation.
    We are only using 3 dc optimisers on the system for some potential minor shading issues.

    So my question is whether what he’s saying regarding the inverter capacity is correct?

    Thanks, Paul.

    • Ronald Brakels says

      Hi Paul, Ronald here.

      Inverters can require a minimum number of panels be connected to each inverter MPPT (Multiple Power Point Tracker). Your inverter will have two of these. The number of panels needed depends on the type of inverter. You can check this at the Fronius configurator which is here:

      https://fronius.solarconfigurator.de/solar.configurator/quick

      And the youtube video on how it works is here:

      I don’t know what your exact inverter model is but after a quick look it does appear the configurator will allow you to put more than 10 panels on the north facing section of roof. But there could be other reasons why the installer recommends a 7/10 split such as shade issues or it simply may be difficult to fit more than 10 panels on the north facing roof.

  22. I have a new system on a new house with 9 North facing panels and 21 West facing panels. I am seeking some efficiency gains so have asked the installer (local electrician) about wiring and panel facing. Apparently (info from speaking with electrician as they have not been able to provide me with a diagram) they have wired up the system as 15 + 15, not 9 + 21. The inverter is Fronius 8.2-3 Symo.

    My understanding is that due to Australian standard (ASNZ 5033 clause 2.1.6) the panel facings should all be on one string (i.e. West and North separate). Alternatively we could parallel the 9 north panels with 9 of the west panels into 1 MPPT. The other MPPT could have the 12 other west panels in a single string.

    Does this sound correct?

    • Ronald Brakels says

      Hi Drew

      If your system has north and west facing modules on the same string that would violate installation guidelines unless they have optimizers. Section 7.1.3 of the Clean Energy Council Install And Supervise Guidelines For Accredited Installers states:

      “7.1.3 Modules that are electrically in the same string shall all be installed at the same tilt angle (±5 degrees) and orientation (±5 degrees), unless using DC conditioning units or micro-inverters.”

      So unless those panels have optimizers (DC conditioning units) your installer should either install optimisers or rewire it. (Australian consumer law protects you in this case regardless of what warranties the installer may or may not have provided.) The only possible out is if Fronius says that configuration is okay, but this is very unlikely.

      • The installer has finally agreed that it is currently wired poorly. Perhaps my citing of the guidelines spurred them into action (thanks for the name & section #). It does worry me that this installer may have tried the same thing on other less-aware consumers in the past. They initially tried to pass some blame onto us for requesting that some panels be moved (from their initial 30 west-facing setup to our requested “maximum north-facing” which turned out to be 9 north/21 west).

        The agreement that I expect to make this week is to have one panel moved from north to west so that 1×8 string for MPPT1 and 2×11 string for MPPT2 (somewhat akin to the dfiagram in the article above except it won’t be 1×3 and 2×3). This seems to be the best compromise as I don’t think that we can mount any more than 9 panels on the north without some complicated racking.

        Thanks for your advice. Let’s hope that we can now get a little bit more efficiency from our system.

  23. Marcus Kelly says

    Doesn’t having bipass diodes stop the shaded panels from reducing the power output of the other panels?

    • Ronald Brakels says

      Hi Marcus

      Unfortunately that’s not the case. It will still drag down the performance of other panels its connected to.

  24. Hi Ronald

    I have 5.5kw system just installed 2 days ago, inhave 2 face 10 panel is North face 0 tile, 8 panels west face 30 tile, I realised one thing that they installed my system as single mppt. I added my circuit picture. Could you please tell me if this is correct or not.

    https://ibb.co/Yf5tP3S

    Regards

    Serkan

    • Ronald Brakels says

      Hi Serkan

      You should be fine because that’s just a simplified diagram and not a detailed wiring diagram. If you had them send you the proper wiring diagram should definitely show the two solar panel arrays attached to separate MPPTs.

  25. Hi Finn,

    Many thanks for your great work.
    I’ve recently had a few quotes for a 6.6kw system. And one supplier mention that he was only able to fit max 13 x 330Wh panels per string with a Fronius 5.0 inverter. Is this correct?

    Many thanks for any insights you would have.

    Cheers,
    Harry

    • Ronald Brakels says

      Hi Harry, Ronald here.

      DC voltages have to be prevented from exceeding a maximum of 600 volts and I would expect the maximum voltage of a 330 watt panel in a string to be around 45-46 volts. This means 13 of these panels would commonly be the maximum as that would add up to around 590 volts. There can be mild differences between different makes of panels, but 13 is probably the maximum.

      • Thanks a lot for your reply Ronald.

        Yes I agree we only can have 13 panel max on a string on a series configuration due to the limit in voltage per string.

        What if we have a “polystring” configuration which consists of two series of 13 panels, and the two series are wired in parallel and then will be connected to a MPPT on the inverter. Then we still maintain the max Voltage (which is 590 volts as you pointed out, even we will have double the current generated by a series of 13 panels). Then we can in theory can fit 13×2=26 panels on a MPPT?

        I am no electrician nor engineer, and those are what I’ve learned from the net. Please let me know what you think of the above design.

        Thanks again for your help.

        Cheers,
        Harry

        • Ronald Brakels says

          Hi Harry

          It is certainly possible to have two strings of panels in parallel and connected to one MPPT to meet the Australian 600 volt DC limit. The two stings will need to have the same number of panels in them. But what can be done will depend on what the inverter’s MPPT can handle.

  26. Hello Ronald,

    I have 6.6 kw system installed last month with Fronius Primo 5kw International inverter and longi LR6-60OPH 350 watt lid mono.
    14 panels facing north goes into one input of the inverter and 5 panels facing west goes to the others. Voc/V is 38.5 at STC and 35.9 at NOCT.
    After having installed them, my friend told me that the number of panels should be even as odd panels causes less efficiency.
    Then I had looked at the other panels and discovered that the installed panels have much less Voc/V then the other major panels.
    So the questions are,
    Do odd number of panels works as good as even?
    Low in Voc/V affects the performance of solar system?
    Over all, is my solar system on the roof ok?
    Cheers,

    • Ronald Brakels says

      Hi Simon

      Your Fronius inverter can handle even and odd panel arrays without problem. I am surprised the inverter could accept a 14 panels on one MPPT and 5 on the other, as that is a larger difference than I generally see, but the low Voc/V may allow that.

      I had a quick look on the Fronius configurator here:

      https://fronius.solarconfigurator.de/solar.configurator/quick

      But it doesn’t appear to have information for your panels at the moment.

      • Des Scahill says

        I’ve got 23 panels on my Fronius inverter system – 14 face North, and 9 West, and it works fine.

        Depending where you live, there is in fact an ‘optimum split’ for panels. In my case I was able to refine it a little further after playing around with numbers,, taking into account solar azimuth and shading issues along with our consumption patterns, ending up with a 60/40 split. whereas the ‘theoretical optimum’ was 55/45

        As well, unless your roof is perfectly square there can be a problem in finding sufficient suitable space.

        Making the split is worthwhile though, it ‘shifts’ more of the PV generation to later in the afternoon which can be helpful with meal-cooking and air con bills.

        There’s a bit of a trade-off involved. If all the panels face North, you might generate a few more Kwh in total over a year, and get maybe more FIT. Splitting the panels usually means you get more self-consumption – so instead of getting say an 8c feed in tariff, you instead reduce your usage, saving you (say) 26 cents per kwh in electricity costs.

        In other words, its not the ‘total kwh generated per annum’ that matters, maximising your self-consumption is more financially beneficial and tends to insulate you a bit better against the possibility of rising kwh charge rates too.

  27. Hello,
    Hoping someone can confirm this is the best install option please, for a 6.6 system, SMA 5 AV-41 inverter with 20 Seraphim blade 330w panels. My roof is unusual with various points but there is no shade. I want north, east and west facing panels – due to limited spaces, can’t have all on the north. The installer has recommend 10 on the west side and 6 on the north using 2 strings to the inverter and then add remaining 4 panels to east side using optimizers. Does this install scenario sound like I’ll get the best power generation? We discussed microinverters but the added price was too high. I’m located in Melbourne. I’m home all day so power will be used all day. Thank you.

    • Hello again. It would be lovely if someone could please respond to my message above dated January 7th as my install is scheduled for next week…. I don’t fully trust the installer so want to know if the experts here think the configuration will work well for me. Thank you!

      • Ronald Brakels says

        Sorry no one got back to you, Karen.

        As the four panels on the east side have optimizers I presume that arrangement will work, although it would require someone who knows the details of SMA inverters to be certain. But solar systems are rarely designed incorrectly. If you are concerned about the installer, I recommend checking their online reviews and getting an idea if they do good work or not. If you see there are people complaining about major unresolved issues you may want to consider cancelling, but if there aren’t any serious complaints then chances are you have someone who does quality work.

        • Thank you Ronald. They’ve got great reviews but theres been some mix ups and wires crossed and if I hadn’t educated myself I think I would have ended up with an inferior system.. e.g. The first quote had all panels facing west and an older model SMA which was asselbled in China, versus the new ones made and assembled in Germany. The solar company owner has actually told me that most people don’t query anything and are happy to accept the quoted products and panel layouts. I’m not like that haha. So that’s why I thought I should seek advice here. Thank you once more – you’ve put my mind to rest.

  28. Anton Ravi says

    Hi Finn,
    Thanks for the infor in regard to solar power found in your site.Grate.

    I am planning to install a 7.9 kw Solar system with fronius 3 phase 6kW inverter as I have three phase.
    My day time usage is 15-20 kWh as we all work from home now and my daliy usage is 35 kwh.
    Due to my roof orientation the installer advised that he can place 24 panels x 330w (7 North,8 noth-east and 9 West).
    As per the specifications the inverter have 2 Mppt and my understaing that it can handle only 2 directions.
    But the installer advised that the inverter can handle 3 directions?

    Can you please advise/Confirm if it is okay to have panels installed in 3 different directions and with no/very
    less impact on the efficiency.
    Also he gave a another option to install a 5.9 kw Solar system with fronius 3 phase 5kW inverter 18 panels x 330w (8 north and 10 west).
    Other option is to use optimizers/Micro inverters which are expensive.
    Shading is not an issue and it is a double story house.

    Can you plaese advise which one is best for me?

  29. Hi Finn/Ronald,

    Great website! Am quite new to solar so this might be self evident to some. We are near Noosa and about to build a new home and will probably be putting a 6.6 Kw system on the north facing skillion roof with a 5 Kw inverter. By far the largest electrical load will be a full ducted aircon system and pool with heatpump (for year round swimming) consuming around 5Kw each. LPG is used for hotwater and cooktop and all lighting is LED or CFL. My question is this: If the load in the home is greater than what is being currently supplied by the inverter, is just the balance imported from the electricity provider. The basic diagrams I have seen of solar systems doesn’t seem to show this as the grid power is shown to enter the meter board in parallel to the inverter. I would have thought the power from the grid would have entered via the inverter so it can control what is supplying the power to the household circuitry.

    • Ronald Brakels says

      The solar inverter will only take DC current from the solar panels and convert it to AC power and supply it to the home and then the grid if there is a surplus. It otherwise won’t have any other effect on your home electricity. (Except maybe draw a watt or two at night.) There is no active control over the power supply. If your home is using more power than the solar system is producing the electricity meter will simply register that your home is using grid power and if your home is producing more solar power than it is consuming the meter will register that you are sending electricity into the grid that you will receive a feed-in tariff for.

      As pools and ducted air conditioners tend to use a lot of energy, you may want to consider a larger system. If you will have three phase power this is simple, but if you will have single phase power you can still get a larger system by getting an inverter that’s larger than 5 kilowatts but export limiting it to 5 kilowatts.

    • Geoff Miell says

      Keith,
      You state:
      “We are near Noosa and about to build a new home…”

      May I suggest before you get too deep into specifications for your home, that you look at Alternative Technology Association’s (ATA’s) “Are We Still Cooking with Gas?” report. dated 25 Nov 2014. The report is getting a bit long in the tooth but IMO this statement remains true:
      “While the efficiency of electric space and water heating appliances is continuing to improve, that of gas appliances is forever limited.”
      See: https://renew.org.au/wp-content/projects/CAP_Gas_Research_Final_Report_251114_v2.0.pdf

      Tim Forcey, based in Melbourne VIC, runs an open Facebook group “My Efficient Electric Home” that may be of interest to you.
      See: https://www.facebook.com/groups/MyEfficientElectricHome/

      The evidence I see indicates, despite the current oil and gas glut we are seeing now, it’s likely we will see a post- ‘peak oil and gas’ world within this decade – that means a sustained decline in global gas supplies. Per BPSRoWE-2019, USA was the world’s largest gas producer in 2018 at 21.5% global share, but had an estimated reserves-to-production of 14.3 years, most of which is shale gas. US tight oil and shale gas have steep production decline rates, so unless more wells are continually drilled to bring on more new production, then aggregate production will fall.

      The latest Baker Hughes operating (oil + gas) drill rig count for US:
      Last count at 301 rigs on 29 May 2020, down 17 rigs from 22 May 2020, and down 683 rigs from 31 May 2019. So, that means more than two-thirds of rigs that were operating this time last year in the US have been taken out of service.
      See: https://rigcount.bakerhughes.com/rig-count-overview

      My point: Don’t assume gas will remain abundant and affordable for much longer. Best to start with an efficient all electric home now to avoid retrofitting/replacing later.

      Good luck.

  30. Jerome Amos says

    Hello Finn,

    You might have answered this question somewhere already and it seems obvious from reading the previous inquiries.

    Are there only 2 MPPTs on an inverter or are there inverters with 3 MPPTs on them?

    I am asking because I am debating if having a 6KW SMA tripower string up from 2 strings N-E and S-W rooftops. No shading issues.

    Or a much costlier 5KW SolarEdge with optimizers connected to 3 strings: N-E, N-W and S-W rooftops.

    Or if possible and less costly all 3 strings on a 6KW with 3 MPPT inverter?

    Thank you

  31. Dave Wise says

    I have 3 roof levels all facing north. I want to utilise all the levels for the panels. How can you optimise the solar output with this situation? Thanks for your time.

  32. Hello

    I have had quotes for a 5kW SMA Inverter with 20 330 panels. I explained that my usage was mainly late afternoon / evening.

    We have limited space on the North facing roof, ample space East and West with no shading issues.

    Quote 1: advised 7 panels to the North and 13 to the West.
    Quote 2: advised and even match East and West would be best.

    Can you advise if one is better than the other

    • Ronald Brakels says

      Hi Mark

      The system with the north facing panels will produce perhaps 5% more energy overall and if most of your electricity consumption is in the afternoon then more west facing panels will help with that. So I would presume, all else equal, having the system with north and west facing panels would be best. Having panels facing east and west would be more suitable for a household with a more even split between electricity consumption in the morning and afternoon.

      • Cheers Ronald

        Thanks for the input, it was kind of what I was thinking, but it’s reassuring getting advice from someone who has knowledge in this field.

        Thanks

        Mark

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