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Enphase M-190 Microverters

09 Nov 09 | Solar Electric

I had a chance to work on the installation of a Photovoltaic (PV) array using the Enphase M-190 inverters last week.  I must admit, when I first heard of the concept of Microverters, I was a bit of a skeptic.

Adding many more active parts to a system seems like an invitation for failure.  Placing those inverters outside attached to a solar panel, sometimes on a hot roof, also seems like a problem.  Finally, investing in a brand new technology from an unknown company might not be wise.

Enphase-M190-72-240-S11-MC3-2

But then I installed them.  Here is what I like:

  1. Each panel now operates at its own Maximum Power Point.  Since I have worked in electronics for over 20 years, I realize that every transistor (thus every panel) has slightly different characteristics.  Having an inverter that is able to adjust for these differences increases efficiency.
  2. Some array shading issues are mitigated.  In the Northeast there are a lot of trees.  Leave any plot of land alone for about 10 years and there will be trees growing on it.  Many home owners do not want to clear cut their property.  Using these inverters means that partial array shading will not be as devastating as it would be with a single large inverter.  Basically, each panel acts as its own mini solar array, thus if one panel is shaded, the other unshaded panels are working at full power.
  3. The warranty is for 15 years, most inverters are warranted for 5 years.
  4. The array wiring is extremely simple, it would be difficult to install these incorrectly.
  5. The array is scalable.  If a homeowner Can’t afford 100% PV power right now, install what they can afford, then revisit the situation later.
  6. May be a good solution for apartment dwellers and other renters using temporary mounting systems.
  7. Can be used in an array with different size PV modules.
  8. Monitoring service available.  Monitors and logs output of each solar module in the array, thus can track array performance and be notified of any problems.

Obviously it is better to have a shade free solar site than to compromise the efficiency of the PV panels installed.  However, this makes it a viable option for sites that have a mostly shade free solar window (9am- 3pm year round), and can live with some reduction in array output.

Regarding the issues raised in paragraph two, I think the Enphase record speaks for itself.  I would recommend these to any customer who was looking to do a scalable system, or a system using different sized or types of PV panels.  I would install these on my own house and recommend them to other people as well.  I would be very surprised if other manufactures do not come out with a miniverter product lines.

Unfortunately, the power companies around here are a little behind the curve when it comes to new or innovative technology.  One in particular has been difficult to deal with for establishing a net metering account.

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09 Nov 09 | Solar Electric
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Reader's Comments

  1. Eric | December 11th, 2009 at 6:02 pm

    We just installed 8.4 kW of M-190’s, 3kW more this weekend. I like them to an extent:

    1. The module-by-module monitoring offered by Enphase is GREAT!
    2. The shade-control factors offered by MI’s in general is GREAT!
    3. Don’t use these with Clicksys Racking unless you install the sliders for your midclips FIRST! (Jeez we learned that lesson the $hard$ way!!)
    4. They make sense financially up to about the 5kW level. Then, the cost ($160 ea) outweighs the benefits of a central inverter in my mind. ($4k for MI’s vs. ~ $3.5k for a central inverter)

    All in all, our customers are very stoked on the visual monitoring, and I particularly like the email notifications. Starts the warranty process automatically!!~

    Solar Epiphany

  2. Paul | December 11th, 2009 at 6:27 pm

    Hey Eric,

    I am working on a 5 KW system this weekend using the M210 inverters with the Sanyo 215N panels. Should be fun. One thing that I have run into is the utility company doesn’t like them. Each time I do a system test and certification, I go round and round with the engineer about leakage current vs. monitoring current. I am working out a standardized acceptance testing procedure for New York State.

  3. Eric | December 14th, 2009 at 1:15 pm

    Interesting. Seattle City Light has no problem with them. They (and We as installers) like the idea of the inverters automatically shutting down on the roof when grid voltage is down. Of course we install an accessible disconnect for them as well. I’d like to see the testing procedure you come up with.



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