So how bad are string inverters vs microinverters?

[Mike 134]

Well nomadh if you want to connect to the grid and they follow the 2017 or later NEC you'll need some type of electronic doodad on the roof.

[Mike 134]

I wanted to add a few tigos to my system for shading and calling 5 places it seems no one even understands what I'm taking about . I was wondering if tigo went out of biz. Was it swallowed up by Smi?

about the 120 cell panels, so was he scamming to do that? You think using 60 cell would have been much worse?

try these guys
Tigo Energy Solar Inverters | CED Greentech

[SunEagle]

the big advantage of the string inverter was cheaper and simpler, no electronics on the roof. If you need a module at each panel then you killed the string inverter market. In fact if someone wanted to do something like it it is in fact illegal you need what used to be a simple string inverter plus another 29 or 30 electronic breakable doodads on you roof causing problems.

Oh. It is illegal to not have the shutdown feature if your AHJ follows the local and NEC rules. If you don't believe me you can try contacting someone in your area that follows the rules. Just be aware that I will not tolerate someone on this forum that supports breaking the law.

[oregon_phil]

I wanted to add a few tigos to my system for shading and calling 5 places it seems no one even understands what I'm taking about . I was wondering if tigo went out of biz. Was it swallowed up by Smi?

about the 120 cell panels, so was he scamming to do that? You think using 60 cell would have been much worse?

No scamming on the 120 cell panels. They can be more tolerant of shade and everybody makes them now as opposed to 4 years ago. He's just using today's technology which I think is fair.

[bcroe]

No scamming on the 120 cell panels. They can be more tolerant of shade and everybody makes them now as opposed to 4 years ago. He's just using today's technology which I think is fair.

Maybe I am missing something, but it seems to me, claiming the half cut panels
are much shade tolerant appears to be a gross exaggeration. There may be some
gain if a single cell is covered (I read), but the case here is shade sweeping over a
panel (or array), they will not help at all. Just how are they any better than the 3 in
cells used before we figured out how to make 6 in cells? I see way more conductor
penetrations for connections, more opportunity for moisture penetration. Bruce Roe

[oregon_phil]

The 120 cells are arranged like two smaller 60 cell panels in parallel that share 3 bypass diodes so there are 6 "zones" per panel instead of 3. I agree the type of shade would determine whether or not any benefit would be realized.

[foggysail]

Gees, my understanding of solar would cause me to question why one would want to use a string inverter other than saving cost maybe. I have a lot of planning yet to do before I can speak with a knowledgeable authority. A string inverter allows a system efficiency loss when a panel fails to operate at MPP due to shading. Properly designed individual inverters always operate at MPP

[bcroe]

Gees, my understanding of solar would cause me to question why one would want to use a string inverter other than saving cost maybe. I have a lot of planning yet to do before I can speak with a knowledgeable authority. A string inverter allows a system efficiency loss when a panel fails to operate at MPP due to shading. Properly designed individual inverters always operate at MPP

It is going to be much dependent on the application. The ground mount array
here has no need for rapid shutdown circuitry. With the longest string wire
loop approaching 1000 feet, the higher operating voltage gives a huge
improvement in the feed wire cost-system loss tradeoff, besides just being
far simpler.

I read 2% or 3% efficiency increased losses from a shaded string configuration.
BUT that condition lasts such a tiny fraction of the day here (before or after
everything is shut down), that the daily percentage loss is really tiny. It is
far less than the wire loss savings.

Yes strings have no individual panel monitoring. In 9 years that has had no
maintenance impact here. For entertainment, before solar we in the country
just settled for watching the grass grow.

I strongly suspect, the #1 reason for micros is the no brainer design. Bruce Roe

[SunEagle]

It is going to be much dependent on the application. The ground mount array
here has no need for rapid shutdown circuitry. With the longest string wire
loop approaching 1000 feet, the higher operating voltage gives a huge
improvement in the feed wire cost-system loss tradeoff, besides just being
far simpler.

I read 2% or 3% efficiency increased losses from a shaded string configuration.
BUT that condition lasts such a tiny fraction of the day here (before or after
everything is shut down), that the daily percentage loss is really tiny. It is
far less than the wire loss savings.

Yes strings have no individual panel monitoring. In 9 years that has had no
maintenance impact here. For entertainment, before solar we in the country
just settled for watching the grass grow.

I strongly suspect, the #1 reason for micros is the no brainer design. Bruce Roe

I also think that most of the installers rely on unknowing people to think they need micros or their system won't work as well just to get more money from them. IMO they are just shysters' preying on people.

[jflorey2]

I also think that most of the installers rely on unknowing people to think they need micros or their system won't work as well just to get more money from them. IMO they are just shysters' preying on people.

To be fair, a large portion of those installers really believe that microinverters give you significantly higher performance in partial-shade situations. They are as vulnerable as anyone else to sales tactics. And recommending a good microinverter system (like. say, Enphase) is not a bad recommendation, even if there's not much performance gain by using them.

[oregon_phil]

Gees, my understanding of solar would cause me to question why one would want to use a string inverter other than saving cost maybe. I have a lot of planning yet to do before I can speak with a knowledgeable authority. A string inverter allows a system efficiency loss when a panel fails to operate at MPP due to shading. Properly designed individual inverters always operate at MPP

The OP's video in Post #1 is pretty informative. Also, I can run my SMA string inverter without connecting to the cloud. Some of the postings regarding Enphase say cloud connect is required in the latest firmware change. This would not be acceptable to me.

[SunEagle]

To be fair, a large portion of those installers really believe that microinverters give you significantly higher performance in partial-shade situations. They are as vulnerable as anyone else to sales tactics. And recommending a good microinverter system (like. say, Enphase) is not a bad recommendation, even if there's not much performance gain by using them.

The problem I have seen is that a system with micro is usually more expensive then a basic string inverter. The sales people are pushing them even if you do not have a shade issue. That to is pushing something that is not needed just to get a price increase.

[J.P.M.]

To be fair, a large portion of those installers really believe that microinverters give you significantly higher performance in partial-shade situations. They are as vulnerable as anyone else to sales tactics. And recommending a good microinverter system (like. say, Enphase) is not a bad recommendation, even if there's not much performance gain by using them.

Every application is different. But, putting lots of smaller capacity and so redundant (and thus in violation of the KISS principle), sensitive to external environment electronics in what can easily be inaccessible places, and in what may often be termed harsh environments are not the path to good design.

Like many things that make life "better", there's more to solar design than chasing perceived but short term economic benefits, and simple efficiency chasing.

I don't cast aspersions on installers who push micros or optimizers, but many solar installers I know don't take the time or make the effort to think critically about the situation. Their job and more often their front and center their goal, is making money by putting solar equipment on other people's property, not designing and installing the most fit for purpose and most cost effective designs for their customers. That's just reality. Besides, if they did, they wouldn't be in business very long. Low ball and low ethics peddlers would eat their lunch. Nobody's fault. It's just the way it is.

If I had a location that needed micros or optimizers to make it work, I'd seriously question the viability of that location as a candidate for a successful solar installation.

Not every residential site is a good candidate for PV, which, for all practical matters, doesn't work in shade. Nothing in == nothing out regardless of how many micros or optimizers get thrown at it.

[Wavelet8]

Where your points are valid and everyone’s situation is different I will offer a few a couple thought for you to chew over regarding the optimizer and micro inverters.


Does kiss apply? I understand the theory of keeping it simple but micro inverters and optimizers are pretty plug and play. Yes, they can be hard to access in the panel array but sellers offer 25 year warranty including labor. Picking up the phone and calling the installer seems pretty simple and failures not costing you anything seems pretty cheap when it only effects a single solar panel vs the entire array.

[oregon_phil]

Enphase doesn't cover labor:

8. Limited Warranty Limitations and Exclusions. a. This Limited Warranty does not include any cost of labor related to (1) un-installing Covered Product; (2) re-installing a repaired or replacement product, or (3) the removal, installation or troubleshooting of the Covered Owner's electrical systems.

and must be connected continuously to the cloud

This Limited Warranty does not apply to, and Enphase will not be responsible for, any defect in or damage to any Covered Products: (1) if the Covered Product is not connected to the internet within 45 consecutive days following the Warranty Start Date and © 2021 Enphase Energy, Inc. All rights reserved. Effective January 31, 2021 continuously connected to the internet thereafter, unless such lack of connectivity is due to causes outside of the Covered Owner’s reasonable