BN12595 said:
I've looked at the warranty description for the M190s, but it only says they will replace them if defective. My question is, isn't this a defect?
It's a good question. I think the metric of "10% lower energy production than neighbors" that Enphase uses is a decent measure for "defective" since, together with the new firmware, it gives the units a bit more time before they need to be replaced. As you can see from the picture I posted above, none of the seven "Grid Goners" that I currently have are close to that threshold right now. Most produce on-par with their neighbors and the worst is only down 4%. What is interesting with the new firmware is that these units are worse when the first fail, then their performance improves until they ultimately fail. The two units in my system with the worst performance right just recently started giving the "Grid Gone" reports. Most of the others used to have lower performance but now show no real drop in production. With the original firmware, these inverters typically would be dead within a couple of weeks. Now they often last for an additional year or more.
There is another statement which Enphase had on the original M190 datasheet (which was removed on more recent ones):
Enphase said:
If someone wanted to pursue Enphase on anything on that datasheet, that might be the best choice. They made the mistake of not specifying that that was a CALCULATED number. In your case, you measured MTBF is around 18 years.
BN12595 said:
They are taking longer to die than others because mine are top of pole mounts that have a lot of air flow under them (I suspect).
Not really. Yours seem about "normal" to me (for M190s). The MTBF of my roof-mounted M190 inverters is about 3X what yours is and member "drees" has 18 M190s that were installed on his roof in March of 2010 and he has not yet had a single failure. Weatherman is on the other side of the equation with an MTBF of only 4 years.
The good news in all of this is that Enphase is honoring their warranty and replacing failures. Yes, we all now have what I call "limp-along" firmware to eek out another year or so from these things, but that is all for the good in my opinion. At the end of the day, it appears that we may all end up with a bunch of next-generation microinverters as replacements that have the potential to allow us to get 30+ years out of our monetary investments. But, yeah, we have had to spend our precious time on these things, as well.
BTW, if you provide a link to your system, I can add it to my spreadsheet.