MicroInverters Problems So Far ?

[Naptown]

We know where every system in the state is. That is the plan

[Shaun]

I can't help but immediately become suspicious of installers who push hard on micros. Naptown, what has your experience been with Power-One micros, if any?

Also, a bit of an aside: my roof dictates a split array design, half facing south, half facing east, for a ~3.75 kW system. I was told a string inverter can leave watts "on the table" as it requires n amount of power coming from the panels before operating, whereas micros don't have this issue. I haven't read that before as a con for strings; is that true?

[sensij]

Micros may turn on sooner in some installations, but the amount of extra energy produced because of it will be insignificant.

[Naptown]

I can't help but immediately become suspicious of installers who push hard on micros. Naptown, what has your experience been with Power-One micros, if any?

Also, a bit of an aside: my roof dictates a split array design, half facing south, half facing east, for a ~3.75 kW system. I was told a string inverter can leave watts "on the table" as it requires n amount of power coming from the panels before operating, whereas micros don't have this issue. I haven't read that before as a con for strings; is that true?

SMA , Fronius ABB etc all make dual moot input inverters.
If you can make the strings work and no partial shading ( such as a chimney that would shade a couple of panels)
Are a good choice.
Even so if you have say 9 east and 9 west two strings one for each side will work with even a single input inverter with little loss. If unequal side to side than a dual input would be necessary.

[solarix]

I've been surprised by the popularity of microinverters - so I can't really speak to the rationale for them too well, but my take on it is they fit into the iphone trend. They should have called them the i-verter.... Putting a small i-phone sized, smart device on each solar panel seems to the new digital generation as the way to go. Its small, its smart, its efficient, its modular, it optimizes the details.... All true, but - ever seen a i-phone, i-pod, i-watch etc last very long? No. A new phone every 2 years is baked into the deal. Reliability is the difference. In order for a solar system to be cost effective it has to simply work, doing its simple little power conversion, for a long time. The enabling advantage of a PV array is how flat out reliable it is. Not 5 years like most appliances, but more like 5 decades. The rest of the solar system needs to take advantage of that. But power conversion electronics will not match the reliability of the PV panels. Ya, once in awhile you'll get a TV that lasts 25years, but that is the exception - the average is 5 years. Choose a reliable brand of solar inverter and put it down on the wall where it can be easily serviced, not spread out under the array where reliability is compromised and service is a nightmare. Don't complicate a solar system trying to squeeze the last little bit of productivity out of a solar panel - you'll just compromise the reliability with the added complexity. Keep it simple. Add on a panel or two if you must, but go for long term reliability and ease of service.
I'll keep saying it - reliability and serviceability is what's important in choosing inverters.

[Shaun]

In terms of reliability, though, what is ABB's reputation?

[paul65k]

Related Question

I understand that one of the major benefits of using micro inverters vs a central inverter is the ability to get the maximum production from each panel when there is a Shading or orientation issue as I do with a tree shading issue that I can not change. In the attached snapshot of yesterdays production (4.2 Kw system) you will see that there are lower producing panels in each of the 2 separate arrays.....would all panels be reduced to these levels of output in a central inverter system or is there a way that a central inverter can manage this dynamic....If so it looks like my overall production could be 20 - 30% lower in my case.

I was told that this is one of the biggest benefits of Micro-inverters.....I'd be very interested to hear from the experts on this issue please??

[Shaun]

I'll keep saying it - reliability and serviceability is what's important in choosing inverters.

Yup, this is the single most important aspect to me. I've talked to about ~10 installers over the past 10 days and all but two of them didn't have any issues with micros. One pushed against micros, recommending a string with optimizers due to the added complexity aspect you mention, the other said that it all really depends on the conditions surrounding each installation, and that I would be better suited for string and optimizers.

Going into my hunt for quotes, I was sure micros were what I wanted, but I'm increasingly convinced that string/optimizers are where the long-term reliability is at.

[sensij]

I understand that one of the major benefits of using micro inverters vs a central inverter is the ability to get the maximum production from each panel when there is a Shading or orientation issue as I do with a tree shading issue that I can not change. In the attached snapshot of yesterdays production (4.2 Kw system) you will see that there are lower producing panels in each of the 2 separate arrays.....would all panels be reduced to these levels of output in a central inverter system or is there a way that a central inverter can manage this dynamic....If so it looks like my overall production could be 20 - 30% lower in my case.

I was told that this is one of the biggest benefits of Micro-inverters.....I'd be very interested to hear from the experts on this issue please??

In a single string, partial shading on one or just a few panels would probably cause those panels to be bypassed, and not hurt the rest of the string. With micros/optimizers, those shaded panels might still be able to produce a little bit of power, but in most cases, it isn't going to affect the overall energy production very much.

If you have strings in parallel or short strings, the micros make a better case. In the parallel situation, you risk dragging the voltage of the unshaded parallel string down to that of the partially shaded string, or in the case of a short string, dropping the voltage below the minimum necessary for the inverter to function.

[solarix]

In terms of reliability, though, what is ABB's reputation?

I don't know about their microinverter product, but my experience with the Aurora string inverter has been not so great. Just replaced another failed on last week. Used them at the time because they were the first with the dual MPPT input feature and were Arizona made, but have had too many failures. Then they came out with the arc-fault feature that was nothing but trouble and haven't used them since. (except one time I needed a low input voltage to convert over an off-grid system that had an array that was impossible to rewire) Had a far-flung install that after going back 4 times to the site to support an ABB tech revising and revising their arc-fault circuit - I said no more...

[albert436]

A few comments/questions.

Naptown, a question about the installs and prices after 2016. I thought I had seen some discussion in the past suggesting that after the tax credit disappears that the install prices will magically drop to about where there were prior to that. Another idea floating around is that the credit will be extended but who knows about any of this.

solarix, that is such an interesting point about the reliability of the panels vs. the little tech parts.

Would you lump the optimizers into the same class as the inverters ?

[solarix]

Yes I lump optimizers into the same boat as microinverters. They don't have the 60hz output circuits in them that the microinverters do so are inherently a bit more reliable but still not a a worthwhile risk to have a lot of them up under the array where serviceability is a problem. We got burned bad by a high failure rate on the early Solaredge product. The newer stuff seems to be better, but still too risky imho.

[albert436]

That's very interesting as the SolarEdge seems to be a popular item with forum members nowadays.

Isn't that supposed to be good also for arrays that have 2 strings mounted in 2 different orientations ?

[DanS26]

................ well what else can we do.

Well, you can look at the published financial statements for the public (ie traded) solar equipment companies. Lots of good information there if you take the time to read and understand what the accountants have to say.

For example, for years the rate of increase in warranty accruals far exceeded the rate of sales growth for Enphase. Big red flag.

[solarix]

That's very interesting as the SolarEdge seems to be a popular item with forum members nowadays.

Isn't that supposed to be good also for arrays that have 2 strings mounted in 2 different orientations ?

There are very few roofs that can't be efficiently handled with a dual input inverter. The main application for distributed inverters is when you have serious shading issues, but even there you are better off solving it by eliminating the shade somehow than by band-aiding the design with module level optimization.