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RegGuheert
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Enphase field MTBF: M190: ~38 Years M215: ~460 Years M250: >300 Years

Wed Mar 06, 2013 4:30 am

I decided to update the title and first post in this thread since the original premise I had was false. There does not seem to be a Phoenix-heat-related issue with Enphase microinverter failures. For reference, you can still read the original unedited post below, if you like.

For reference, please refer to Enphase Microinverter Field MTBF Estimate spreadsheet. For those that have looked at this before, please have another look, as it has been updated by dividing M190 and M215 calculations and I have added a new column for "Site MTBF" due to the extremely wide variations in MTBF seen with the M190s. I have added notes of anomalies for each of the sites where strange performance was observed.

Please note that with the exception of the one site in Troy, IL, none of these sites were selected BECAUSE they had failures. The rest of the sites were selected because they were close to me or to Phoenix, AZ, or I found out about them here or on the NAWS forum.

Here are some facts from the spreadsheet:

M190 (Also includes M380 models):

Number of sites tracked: ~80
Number of inverters currently tracked: ~2500
Total number of device-years tracked: ~8800
Total number of device failures detected: ~129
Overall Field MTBF: ~60 years
Highest site MTBF (with a failure): 337 years
Highest site MTBF (without a failure): >237 years
Lowest site MTBF: 5 years
Oldest site: 4.78 years

The bottom line is that M190 MTBF seems to vary widely by installation. Several of the worst MTBF sites I have found are near here where heat is not a huge factor. As such, I do not think that heat is the major issue with failures so far. I suspect lightning and/or installation quality may be bigger issues at this early point in their lives. I am also wondering if there may have been some manufacturing issues with the M190s in the middle of 2011 when the M215s were just coming online. We may never know.

M215:

Number of sites tracked: ~40
Number of inverters currently tracked: ~1000
Total number of device-years tracked: ~1300
Total number of device failures detected: 1
Overall Field MTBF: ~1300 years
Highest site MTBF (without a failure): >405 years
Oldest site: 2.18 years

While the M215s are quite young, they have been rock solid so far. Only one failure has been found to date. Tiime will tell if this high reliability holds up until end-of-life sets in.

Unfortunately, it looks like the old public Enlighten sites which allow me to see inverter failures will be taken down on September 3, 2013. (But as of today, September 3, 2013, it is still up!) As such, this little experiment may not last much longer. I added a bunch of Phoenix sites recently to see if there is an issue there. Phoenix looks no worse than anywhere else for M190s or M215s. Today, September 3, 2013, I added sites from Petaluma, CA, and Santa Rosa, CA.

All-in-all, this has been an interesting experiment.

If you have any suggestions before the per-inverter data disappears, please let me know.

Original post:

I have been tracking field failures of Enphase microinverters for a while now by watching the public sites for many of our arrays to try to spot the signature of microinverter replacements. So far, I have accumulated over 1200 device-years of operation and see a total of 4 failures in the field, including one of my own. That gives an MTBF of over 300 years.

For your reference, here is my current spreadsheet showing the MTBF calculation:

https://docs.google.com/spreadsheet/ccc ... FAyMHhuc3c" onclick="window.open(this.href);return false;

To see failures, click on the link for the OLD website and then click the "Lifetime Energy" button in the top right. Panels with lower production are potential failures. Verify by checking for shading by looking at the "Past 7 Days". This approach is not foolproof, as there may be some false negatives due to failures very early in life, but those could be considered as infantile failures anyway.

Any, I found an array yesterday in Gilbert, AZ that appears to have a failure about 9 months ago and there is currently a second panel which is not producing. Of course this second failure is not confirmed to be a microinverter until it gets replaced, but I will assume for now that it is. If so, then I see three failures in AZ and one here in VA. But my failure was very early in the life of the array and it could have been caused by improper operation, so it is a questionable inclusion.

Anyway, I'm starting to wonder if we will see a higher failure rate for Enphase microinverters in AZ than in other areas. Or even worse, I'm wondering if these failures in AZ might be the leading edge of the back end of the bathtub curve where units reach their end-of-life.

It's too early to answer these questions, but it does make sense that AZ would be harder on microinverters sitting on hot roofs just like it is harder on most other things. Of course the one site in Gilbert with two failures out of ten could be a bad installation, but it could also simply be a site with particularly high roof temperatures.

Unfortunately, I will not be able to track Enphase failures much longer. Enphase has redesigned their public web pages and I do not see any way with the new pages to see microinverter replacements. I suppose this was intentional to hide that type of information.

If you have an Enphase-based array which is not included on this spreadsheet, please post your URL here and I will add it.

Note to QueenBee, I have your array on the spreadsheet, but I have excluded it from the analysis since it has not reported anything since January. Have you disconnected from Enlighten?
Last edited by RegGuheert on Sat Feb 25, 2017 6:20 pm, edited 10 times in total.
RegGuheert
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2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

QueenBee
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Re: AZ: Canary in the coalmine for microinverters, too?

Wed Mar 06, 2013 8:15 am

Hey, thanks for tracking this kind of stuff. I've got M215s BTW. My panels are currently offline because I redid the roof in preperation of tripling the size of my system. Unfortunately it's taken longer to get people back to put them on. I really need to get things moving since spring is coming.

I've yet to have any failures.

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RegGuheert
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Re: AZ: Canary in the coalmine for microinverters, too?

Wed Mar 06, 2013 1:26 pm

QueenBee wrote:I've yet to have any failures.
Thanks! I've updated the spreadsheet to include your inverters. Please verify it is correct now!

Also, if everyone else that has an array on that spreadsheet could verify that all the data is correct, that would be appreciated! TIA!
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

jspearman
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Re: AZ: Canary in the coalmine for microinverters, too?

Wed Mar 06, 2013 4:52 pm

My Sunpower dealer strongly cautioned against microinverters here, and I'm happy with my production, so it just wasn't worth the risk until they have more years in the area. String inverters have a lot more years on the ground here.

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RegGuheert
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Re: AZ: Canary in the coalmine for microinverters, too?

Fri Mar 15, 2013 4:26 pm

RegGuheert wrote:Any, I found an array yesterday in Gilbert, AZ that appears to have a failure about 9 months ago and there is currently a second panel which is not producing. Of course this second failure is not confirmed to be a microinverter until it gets replaced, but I will assume for now that it is.
My assumption was correct. The second inverter out of ten total in this array was replaced today. That's a 20% failure rate in three years! I wonder if this trend will continue.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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RegGuheert
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Re: AZ: Canary in the coalmine for microinverters, too?

Fri Apr 19, 2013 1:51 pm

Yet another failure in AZ: Zomeworks Trackers.

And this report, complete with pictures, of a system with three failures, the third one looks as if it was blown apart. Unfortunately, I do not know where this poster lives. Hopefully he will add a URL for his system once he reconnects his Envoy unit.

The MTBF calculation on my spreadsheet is dropping. With the new failure in AZ and a system I added nearby me with two failed inverters. I wish I knew the owner. I'd like to learn more about that system.

Anyway, I may be adding a bunch more systems to the calculation soon since someone over on NAWS posted a link showing ALL the Enphase systems, many of which have public URLs: All Enphase Installations. Anyway, this could be interesting for anyone trying to calculate MTBF for systems in your area.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

jspearman
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Re: AZ: Canary in the coalmine for microinverters, too?

Fri Apr 19, 2013 3:44 pm

Does Enphase list a min/max operating temp? I would love to know how hot it gets under a black panel in the middle of July here.

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RegGuheert
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Re: AZ: Canary in the coalmine for microinverters, too?

Fri Apr 19, 2013 5:42 pm

jspearman wrote:Does Enphase list a min/max operating temp?
The M190 has an operating temperature range of -40C to +65C. These are the units that have been failing. But it's interesting that Enphase has written the specifications slightly differently for the newer M215 microinverters:
Ambient temperature range: -40C to +65C
Operating temperature range (internal): -40C to +85C
This is interesting, since the calculations done for the M190 capacitor life were done at +65C, but the dissipation of the two units should be about the same since the efficiency of the M215 is higher. So it implies to me that Enphase is seeing internal temperatures in the M190s up to 85C in some installations. I'll have to look at the temperatures in our inverters on a hot day.
jspearman wrote:I would love to know how hot it gets under a black panel in the middle of July here.
If you know anyone with these on their roof out there in AZ, they should be able to read the temperatures from the secure Enlighten website for their installation.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

LEAFfan
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Re: AZ: Canary in the coalmine for microinverters, too?

Fri Apr 19, 2013 9:36 pm

jspearman wrote:Does Enphase list a min/max operating temp? I would love to know how hot it gets under a black panel in the middle of July here.


I have a roof temp sensor, and I believe it hit 170-180F last summer. I don't have Enphase micros (have Honeywell/Exeltec), but Monday will be the seventh one to be replaced out of 20. The one Monday is a replacement for a replacement.
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drees
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Re: AZ: Canary in the coalmine for microinverters, too?

Fri Apr 19, 2013 10:22 pm

Anecdotally, it seems that if a site has one failure, it appears that it is more likely to experience additional failures. It seems that there may have been some bad batches here and there resulting in premature failure. Specifically with the M380. The M215 should be more reliable than the 190W inverters.

Either way, heat will speed up the failure rate of electronics, just as it speeds up capacity loss of lithium batteries.
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