Discover How Micro Inverter Solar Panels Cope With Shade

As a true solar geek, I can’t think of anything better to do at 7:30 on a Friday evening, than log in to my solar panel monitoring system.  While most folks are settling down to Friday Night Footy, you’ll find me checking out how much power my 6kW of micro inverter solar panels are producing as the last rays of evening sun scatter across my roof.

As I logged in tonight to see a respectable 1.2kW being pumped out, I noticed that the monitoring system was providing a great example of one of the benefits of microinverter technology.

If you have a gander at the live monitoring screenshot below you’ll see that I’ve highlighted the position of my wood burner’s flue and the approximate shadow it casts as the sun goes down.

solar panel monitoring

The red circle is my flue. I’ve drawn on its 7:30pm shadow.

Now, the interesting thing to note (for a solar-geek anyway) is that the panel next to the flue is at 10W and the panel next to it is 37W.  This compares with all the other panels which are sitting pretty at about 54W. Obviously the 2 underperforming panels are suffering from the flue’s late-evening shadow.

But the cool thing is that the shadow is only affecting those 2 panels. The other 22 panels are rocking along without any reduction in power giving a total of 1.2kW in the late-evening sun.

If I had a central inverter and all these panels were in series, then all the panels would be forced to the same power as the worst performing panel.

In other words I’d only be getting:  24 x 10W = 240W from the system as a whole. 80% less power!

For a rundown of both the advantages and disadvantages of microinverters I’ve put together a summary infographic here.

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. robert bell says:

    the feasability of converting to microinverters at the conclusion of the
    GFIT in NSW.I will possibly upgrade mys 1.5Kw system at that time depending on incentives .What are your thoughts on this idea?

    • I honestly think it would be cheaper to install a whole new 2kW system with microinverters that modify an existing system! Also you could do this now without affecting ypur GFiT.

      • A vagrant thought:- covering all bets. What about the opposite case? If circumstances change and DC power is required is it possible to remove the micro-inverters and reconnect the system to run DC/charge remote battery-banks, etc.?
        I presume the ‘AC panels’ produce similar outputs as ‘standard’ DC ones?
        Jason

        ps _ I note the links you provide are being very coy about publishing pricelists; are they really that much more expensive?

  2. What’s the going price for a 3kW-ish microinverter system nowadays? Do they seem to be getting more popular?

  3. Hi Guys

    Good site…
    My background: badly shaded house on coast in West Oz. Sep 2013: Installed 3Kw of Renesolar panels (12 * 250w) with 6 APS mini-invertors & APS ECU for $5,000. Finn Peacock please note price – $1,000 to $2,000 less than you, no special price gouging involved at my end.
    Result: system works really well*. Atypical coldest winter for years had net -226Kwh over 2 months, -58Kwh for next 2 months. Overall in 18 months, sent 5473 to grid, received 3673 back (and got slugged for the “privilege”).

    My question: given too many power outages here, which would you do first (given fairly limited budget) installing an isolation switch (circa $1500), installing a few more panels & inverters (about $3,000 for another 2Kw) or installing some battery backups and going off-grid altogether (cost unknown to me yet)?

    Thx

    Arron
    * Except a massive TV & radio problem from the micro inverters. Solved by moving the actual radio and the TV aerial. To their credit, the installer helped me troubleshoot & fix the issue.

  4. Graeme Reid says:

    Hi Finn
    I have been surfing the net for a few years trying to get answers that are meaningful and understandable regarding solar power for my home. Your web site covered all my concerns and eased my worries such that I now await a quote from your recommended installers. I have had a couple of quotes in the past year but was dazzled by jargon and disappointed that the consensus was that because my installation would face west I would not get a great benefit from solar! Your site suggests otherwise so I wait eagerly for a positive offer at a respectable price.
    You talk my language Finn so thank you for your efforts in clear communication.

  5. I requested three quotes and you have sent through the information. Thank you. I had a quote from a licensed installer for 20 solar panels, not from one of the three you sent through. The Installer came to my house and said it would be better to place the 20 panels on the flat roof on the garage, and not on the steep gable roof on the house. You will get more sunlight on the flatter roof rather than the steep gable roof. Reading on your website there appears to be an indication installation will be better placed on a flatter roof rather than a steep gable roof. One of the three Installers you emailed to me, contacted me today and quoted a 3kW and stated it would be ideal in placing the solar panels on the steep gable roof. The 3kW system consists of 12 panels a big difference to the 20 panels quoted by the other installer. The Installer who phoned me today stated most of the solar panels are made in China, all are made overseas. One of the companies you emailed through to me indicates the following “Not compromising on quality, we only use Local Australian owned solar panels”
    Questions:
    Who is right where solar panels are made?
    Are Australian solar panels better than overseas or vice versa?
    The quote I have for 20 Solar Panels is the same as the quote for 12 Solar Panels. Who is quoting way over/under the needs for a $500.00 quarterly electricity bill?
    Where should the Solar Panels be installed on the flatter roof or the steep gable roof?

    • Hi Ian,

      The 3 Installers I sent your details to were: SAE, Beyond Solar and Energy Aware.

      I’m not sure how steep your gable roof is, or which direction it faces, but you can compare the energy yield of the gable with the flat roof with this table:

      https://www.solarquotes.com.au/installers/sydney/#yieldtable

      For example, if your gable is 60 degrees from horizontal, north facing, you’ll get a 90% yield compared to the perfect angle with is 30 degrees.

      The bonus of a steep roof is that you get more winter generation – and less summer generation, so you get a more constant performance through the year, This is generally an advantage.

      As you can see from the table, a flat roof will give an 87% yield. I don’t like flat roofs with regular panels – as the water pools – and can lead to premature seal failure on the frames. They also do not self clean in the rain.

      I’d seriously consider the gable roof.

      Be careful with the language you hear. The *only* Australian Made panels are Tindo Solar. “Australian Owned” means they could be made anywhere.

      There are lots of good Chinese Panels – if you get a Tier 1 panel – you should be fine:

      http://www.solarquotes.com.au/blog/tier-1-solar-panels-sold-pup/

      Typical costs are here:

      http://www.solarquotes.com.au/how-much-do-solar-panels-cost.html

      Hope That Helps,

      Finn

  6. Roger Fletcher says:

    Finn,
    I’ve read comments the Enphase M250 inverters dare note as well suited to 60 cell 260W panels as the M215 or M230 Models

    Any insights as to why this would be?

    • In terms of electrical compatibility – this tool will tell you which Enphase micros your particular panel will work with:

      https://enphase.com/en-us/support/module-compatibility

      You’ll probably find that all the models are compatible with your 60 cell panels.

      I think the ‘well-suited’ argument might be about economics, and inverter oversizing. Generally the lower powered micro inverters are a bit cheaper – so it can be more economically efficient to pair a 260W panel with a 215 to 230W inverter, because the 260W panel will very rarely operate above 210-230W.

      This blog post goes into great detail on the concept of making you panel wattage greater than your inverter wattage. The post is in the context of string inverters – but the same logic applies to micro inverters:

      http://www.solarquotes.com.au/blog/oversizing-solar-arrays/

      P.S. The 230W Enphase is an ‘S’ series: ‘S230’. i.e. 5th generation. If you can get that for the same price as the ‘M’ series go for it – as it should be slightly better performing and even more robust than the 4th generation ‘M’ series.

  7. Tony Breen says:

    Finn, as I have a lot of big trees around my house , can you tell me who in Western Australia Mandurah 6210 can do the Solmetric SunEye roof test. to sed iff it is worth getting a solar array system

  8. John McCowan says:

    Hello Finn,
    I’m due to get some quotes from your system in the next few days, but looking for some information which would help me talk sense to the potential installers. I’m in Perth, have a 3phase installation on a recently completed house using about 40kWh per day, am on a flat rate (don’t think there’s any other option here) and have a Landis & Gyr E350 3phase 4 wire meter badged by Western Power as U3300 and dated 2013.
    I’ve only a small area available for panels which is subject to heavy shading in the afternoons.
    My dumb question is:
    Do the microinverters, which I suspect would be essential in this case deliver entirely to one phase? What happens if the power use at the time is not on that phase? Do I end up exporting cheap power on the PV connected phase and importing expensive power on the demand one?
    Hopefully the meter instantaneously nets out the power imported/exported irrespective of phase so when my demand on any combination of phases exceeds that which I’m generating (on whatever phase that is) my meter is showing my consumption as the demand less the generation. Common sense suggests that’s probably what happens, but that’s often in rare supply and I’d like to be sure.
    Would appreciate your wise words.

  9. John McCowan says:

    Hello Ronald,
    Many thanks for raising my consciousness on this. I suspected I was fretting about nothing and you’ve confirmed it. Thanks again. Will clue myself up further with your link to Finn’s note.

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