Three estimates - Different Panels

[robbyg]

To those who say "hot electronics are unreliable", please understand that it's not that simple. Hot electronics that is engineered for that temperature and uses components that are reliable at that temperature will be reliable. As a simple example, you can buy electrolytic capacitors that are rated for 85C, 105C, 125C, and 150C operation. The difference is materials and construction, not just specs. If the inverter builder uses high-temperature capacitors, they will get much longer life. Yes, the roof can get to 130F (54C) and the inside of the microinverter can get even hotter. But that's still tepid for 125C or 150C components.

Don't forget that the insides of a string inverter is also very hot because it is processing many kilowatts.

Sorry for ranting.

It's all very relative. A 150C rated electrolytic capacitor will last a lot longer at 50C vs 150C. As you stated the roof can get very hot at 54C, in reality they can get up to 60C and lord knows how much hotter it could be inside that inverter, especially if its sandwiched close to the roof.

Capacitors are not the only thing that does not do well in heat, almost all semiconductors start to have problems when they get hot. Typical Mosfets etc will work at up to about 120C max with some specialized ones having a max of 220C. The problem is that almost all electronic components degrade with higher heat and have a shortened life span. The big difference with String Inverters is that you can keep that heat down to a level that makes heat not an issue for the components.

As for Data on this kind of thing, I would not trust anything that comes from people in the industry. You would need a reputable independent group to do a long term study. The problem is that before you even get past a couple of years of testing the product, it has probably been replaced by a newer model. I would seriously consider Micro Inverters for a ground mount installation as Enphase seems to have excellent warranty support. Of course that warranty is not going to help you if the panels are mounted on the roof of a two story building and the one that is dead is somewhere in the middle. Your going to need a truck roll for that and it's going to be very expensive.

[bob-n]

"can anyone provide any non-anecdotal, unbiased, evidence-based data on the failure rate / TCO of micro-inverters vs string inverters?"

This report is the most objective thing I've read on the subject.

https://www.mcelectrical.com.au/micro-inverters/

I'll quote a few paragraphs from the report below.

"In the last five years, we have installed about 1550 micros on 77 homes. Most of these systems are over four years old, so they are close to halfway through their ten year warranty period. To date, we’ve had only four microinverter failures (0.25%) and a few communication issues that I’ll address later."

"You could say that 4 out of 77 jobs means about 5% of our Enphase jobs have had a failure. That’s bad compared to a quality string inverter like Fronius. However, that’s not a fair comparison. Enphase’s “decentralised power topology” ensures that if one microinverter fails, you’ll only lose the production of one panel. When a string inverter (like Fronius or SMA) fail, you lose the production of the whole system."

"SolarEdge is a fairer comparison. SolarEdge uses both rooftop power electronics (optimisers) and a central point of failure (the SolarEdge Inverter). How does SolarEdge fair for reliability? 34% of our SolarEdge jobs have had at least one fault. 11% of our SolarEdge inverters have failed so far, taking the whole system down."

"Every solar panel has three bypass diodes to protect them from the shade. If they activate too often because of severe shade, then they may fail, and you will lose 1/3 of the production of your panel. We have only ever picked up six blown bypass diodes from the 5000+ panels that we have installed with individual panel monitoring (Enphase, SolarEdge or Tigo). However we’ve had four Enphase microinverters, and 56 SolarEdge optimisers fail."

My take-away from this report is that Enphase reliability is very good, and much better than SolarEdge optimizers and much better than SolarEdge inverters. Optimizers are on the roof just like microinverters, so still expensive to replace. And any repair job is a hassle, because it requires debug, vendor support, and field work. Don't underestimate the challenge of debug. Every failure is different.

To those who say "hot electronics are unreliable", please understand that it's not that simple. Hot electronics that is engineered for that temperature and uses components that are reliable at that temperature will be reliable. As a simple example, you can buy electrolytic capacitors that are rated for 85C, 105C, 125C, and 150C operation. The difference is materials and construction, not just specs. If the inverter builder uses high-temperature capacitors, they will get much longer life. Yes, the roof can get to 130F (54C) and the inside of the microinverter can get even hotter. But that's still tepid for 125C or 150C components.

Don't forget that the insides of a string inverter is also very hot because it is processing many kilowatts.

Sorry for ranting.

[J.P.M.]

I received a new quote today that wouldn't need to update my 100amp electrical panel. The only catch is that I wouldn't be able to meet the 7100 kwh I use per year. They would install 13 REC370AA panels which gives 4.810 kW Total Solar Power or 6,318 kWh per year at $12,361. What do you guys think?

First off, is that $12,361 before of after fed. tax credit ?

You've got to do the math with more than a back of the envelope analysis.
Assuming the 6,318 kWh/yr (BTW, probably +/- 10 % or so due to weather variation yr./yr.) is a reasonable working #, , dig into your POCO's rate structure(s) and see what you'll pay for those 6,318 kWh if you didn't have PV. The digging into the POCO rates is probably necessary because the highest rates are not what you probably pay for most of your electricity, and lots of other things like T.O.U. rates and other stuff makes the digging necessary for a reasonable guess. Most folks give up on that analysis and screw themselves by paying too much/STC watt for what are usually oversized systems.

Anyway, divide that guess of annual electricity cost into $12,361 (less any tax credit) for a real sloppy guess at how long it'll take to recoup the investment of $12,361 (less fed. tax credit). Then, compare that to the rate of return you might get if you put that $12,361 into another form of investment.

To do a proper financial analysis is a lot more involved than the above, but that will get you started.

BTW, in many cases the most cost effective use of the money for a PV system is for one that supplies less than 100% of the annual load. Also, oversizing a system is usually the short straight road to a non cost effective system. When buying PV, what you don't know will cost you money. Get informed.

[SunEagle]

I received a new quote today that wouldn't need to update my 100amp electrical panel. The only catch is that I wouldn't be able to meet the 7100 kwh I use per year. They would install 13 REC370AA panels which gives 4.810 kW Total Solar Power or 6,318 kWh per year at $12,361. What do you guys think?

Well the math comes to $12361 / 4810 watt = $2.57/watt. If that is your final cost then it might be worth while but it still depends on what it costs you per kWh, what that comes to in $$ savings and how long you feel it is worth the investment.

[J-P]

I received a new quote today that wouldn't need to update my 100amp electrical panel. The only catch is that I wouldn't be able to meet the 7100 kwh I use per year. They would install 13 REC370AA panels which gives 4.810 kW Total Solar Power or 6,318 kWh per year at $12,361. What do you guys think?

[robbyg]

I agree that finding hard data about failure rates is difficult. None of the manufacturers want their failure rates to be known. I can tell you that I have replaced many microinverters and optimizers including a few systems where all the units were replaced under warranty. Of course, this is in hot Arizona - but never the less, it is way too high a failure rate for me.
Yes, very few customers actually utilize their monitoring beyond the initial "christmas toy" phase of ownership and I recommend against choosing an inverter based on this feature.

Hot running electronic devices are always going to have a shortened life. Real data from these companies is never going to be forth coming and I doubt that any third party would want to take on the task. In some cases you just have to go with your own experience with similar devices.
I have owned lots of Inverters over the last three decades and they always lasted the longest when kept cool and were run at no more than 70% of their rated load. Micro Inverters are working way outside of what I would call an ideal operational environment. If my panels were ground mounted it might be an option but on a high roof it becomes a logistical nightmare. I would rather keep whats on the roof as simple and reliable as possible.

[solarix]

I agree that finding hard data about failure rates is difficult. None of the manufacturers want their failure rates to be known. I can tell you that I have replaced many microinverters and optimizers including a few systems where all the units were replaced under warranty. Of course, this is in hot Arizona - but never the less, it is way too high a failure rate for me.
Yes, very few customers actually utilize their monitoring beyond the initial "christmas toy" phase of ownership and I recommend against choosing an inverter based on this feature.

[solardreamer]

I certainly understand why many installers don't like microinverters due to more difficult replacement work but from a solar owner perspective I like microinverters because I don't want to have an inverter failure to take my entire system down for weeks or longer which seems relatively common for some string inverter brands.

[J.P.M.]

As a dealer, I won't install microinverters because I know down the road I'll be having to do truck rolls to replace them one at a time. I too marvel at how they have become so common in the solar industry. A big part is the 2017 code requiring "module level shutdown" (promulgated by the microinverter companies...) But I find that microinverters are seen as attractive by a culture that just loves cell phones and view microinverters like a cell phone attached to every solar panel. "Oh - I can see on my phone just how each of my solar panels is doing." Ya that's right, now when the less reliable microinverter fails - you'll at least know about it right away.

To your last sentence: As someone who keeps track of solar installs in my HOA, ~ 150+ to date, I get feedback from users.
Seems to me:
1.) Most folks could not care less about monitoring.
2.) Most folks wouldn't know what they were looking at if they did check array/panel output.
3.) Those who do monitor and have a clue what they're looking at quickly get bored doing so as the novelty quickly wears off. That usually lasts less than a month or so.

At least when a string inverter fails, the hapless owner will only need to wait until the next billing - if they bother to read the bill or pay attention to it - many around here don't - to get hit upside the head.

[Spektre]

I don't want to start anything here, but I do find it interesting when people embrace their gut feelings about something as facts.

Case in point: can anyone provide any non-anecdotal, unbiased, evidence-based data on the failure rate / TCO of micro-inverters vs string inverters? I have searched exhaustively and am unable to find actual peer-reviewed studies on the subject. Lots of FUD and manufacturer-sponsored stuff available though...

[solarix]

As a dealer, I won't install microinverters because I know down the road I'll be having to do truck rolls to replace them one at a time. I too marvel at how they have become so common in the solar industry. A big part is the 2017 code requiring "module level shutdown" (promulgated by the microinverter companies...) But I find that microinverters are seen as attractive by a culture that just loves cell phones and view microinverters like a cell phone attached to every solar panel. "Oh - I can see on my phone just how each of my solar panels is doing." Ya that's right, now when the less reliable microinverter fails - you'll at least know about it right away.

[robbyg]

Every situation is different, use what works for you. But micro inverters are a
dumbed down, fits all solution, looking for a problem. String inverters fit in here,
and are producing some performance not practical with a micro inverter.
Bruce Roe

I agree, I would not purchase a system with Micro Inverters. Your just going to be paying year after year for an installer to go up on your roof and replace a Micro Inverter that dies. I would rather stick with one Failure point in Garage than have 14 of them on my roof !
I suspect that this is one of the things that also attracts Installers as they will have maintenance money flowing in year after year once they get enough clients using Micro Inverters.

Also I am still confused on the Benefits of pairing 440W Panels with 350W Inverters. I get what they are saying but just like the puzzling "New Tech" behind SMA's shade fix I would love to see some long term real world data that backs up the claim that this pairing does not affect the average monthly KWH output.

[bcroe]

Every situation is different, use what works for you. But micro inverters are a
dumbed down, fits all solution, looking for a problem. String inverters fit in here,
and are producing some performance not practical with a micro inverter.
Bruce Roe

[SunEagle]

Is there a reason new system comparisons always seem to be "Enphase" vs "SolarEdge"? I know the OP didn't say anything about shading, but an SMA inverter with Tigo's optimizers would work fine in almost any situation.

I have also been approached by solar installers and just about all of the "equipment" that they are pushing have micro inverters instead of string inverters. Maybe Enphase and SolarEdge just have more influence on them then other equipment suppliers.

[oregon_phil]

Is there a reason new system comparisons always seem to be "Enphase" vs "SolarEdge"? I know the OP didn't say anything about shading, but an SMA inverter with Tigo's optimizers would work fine in almost any situation.