RegGuheert
Well-known member
What is the expected life, MTBF, failure modes and maintenance schedule for your PV system?
For reference, here is a Wikipedia article on failure rate.
I'll start. Our system consists of 42 Enphase M190 microinverters and 42 Sharp NU-U235F3 PV modules. You can see details of the system along with pictures in the link in my signature.
LIFE
Enphase estimates the working life of the M190 to be over 20 years. I do not have better data than that, so I will use that.
Monocrystalline PV panels have an unknown life expectancy. Their electricity production gradually degrades over their long life.
MTBF
Enphase calculates the MTBF of the M190s to be 331 years, which equates to a FIT rate of 345 failures per billion hours. This number is pretty close to the actual MTBF I have calculated for systems operating all over North America. (MTBF does seem to be lower in AZ than elsewhere, BTW.) Since we have 42 M190s that gives a total FIT rate of 14,490 failures per billion hours. That means about one microinverter failure every 7.9 years.
Industry tends to feel that PV panels have an MTBF of over 600 years, so I will use 600 years or a FIT rate of 190 failures per billion hours. That gives a fit rate of 7980 failures per billion hours. That means about one PV panel failed every 14.3 years.
I don't know the FIT rates for the mounting system, wiring and breakers, but I will assume they are very low and I will use 0 FITs for my calculations.
Given all that, I expect the overall FIT rate of our system to be about 22,470 failures per billion hours, or an MTBF of 5.1 years. So during the 20 year life expectancy of the microinverters, I expect to see about 3 failures with likely most of those being microinverters.
In reality, we have experienced the failure of one microinverter very early in its life, which was replaced under warranty.
FAILURE MODES
Each of the expected failures should only affect the production of a single panel, so three failures would reduce production of the array by only about 7%, even if not repaired. In reality, one inverter replacement has already been accomplished. Future replacements may or may not happen depending upon whether or not they occur under warranty and where the failures occur in the array. Some inverter failures would require a significant amount of effort to replace while others, like the one which already failed, are trivial to replace.
MAINTENANCE
This system is maintenance free. I do not clean the panels, but rather I count on the rain to wash them occasionally and the snow scrubs them about once or twice a year when it slides off.
SUMMARY
Life: 20 years
MTBF: 5.1 years
Failure modes: Benign
Maintenance: None
If you have an Enphase-based system, you should be able to estimate your MTBF by dividing 213 years (the MTBF of a single panel/inverter combination) by the total number of panels you have. However, since our PV panels and Enphase inverters all sit on our roofs, we can expect those who live in colder climates to experience higher MTBFs and those who live in hotter climates to experience lower MTBFs, just like we see with our LEAFs.
If you have any other type of system, you can make a similar type of calculation to estimate the MTBF of your system.
For reference, here is a Wikipedia article on failure rate.
I'll start. Our system consists of 42 Enphase M190 microinverters and 42 Sharp NU-U235F3 PV modules. You can see details of the system along with pictures in the link in my signature.
LIFE
Enphase estimates the working life of the M190 to be over 20 years. I do not have better data than that, so I will use that.
Monocrystalline PV panels have an unknown life expectancy. Their electricity production gradually degrades over their long life.
MTBF
Enphase calculates the MTBF of the M190s to be 331 years, which equates to a FIT rate of 345 failures per billion hours. This number is pretty close to the actual MTBF I have calculated for systems operating all over North America. (MTBF does seem to be lower in AZ than elsewhere, BTW.) Since we have 42 M190s that gives a total FIT rate of 14,490 failures per billion hours. That means about one microinverter failure every 7.9 years.
Industry tends to feel that PV panels have an MTBF of over 600 years, so I will use 600 years or a FIT rate of 190 failures per billion hours. That gives a fit rate of 7980 failures per billion hours. That means about one PV panel failed every 14.3 years.
I don't know the FIT rates for the mounting system, wiring and breakers, but I will assume they are very low and I will use 0 FITs for my calculations.
Given all that, I expect the overall FIT rate of our system to be about 22,470 failures per billion hours, or an MTBF of 5.1 years. So during the 20 year life expectancy of the microinverters, I expect to see about 3 failures with likely most of those being microinverters.
In reality, we have experienced the failure of one microinverter very early in its life, which was replaced under warranty.
FAILURE MODES
Each of the expected failures should only affect the production of a single panel, so three failures would reduce production of the array by only about 7%, even if not repaired. In reality, one inverter replacement has already been accomplished. Future replacements may or may not happen depending upon whether or not they occur under warranty and where the failures occur in the array. Some inverter failures would require a significant amount of effort to replace while others, like the one which already failed, are trivial to replace.
MAINTENANCE
This system is maintenance free. I do not clean the panels, but rather I count on the rain to wash them occasionally and the snow scrubs them about once or twice a year when it slides off.
SUMMARY
Life: 20 years
MTBF: 5.1 years
Failure modes: Benign
Maintenance: None
If you have an Enphase-based system, you should be able to estimate your MTBF by dividing 213 years (the MTBF of a single panel/inverter combination) by the total number of panels you have. However, since our PV panels and Enphase inverters all sit on our roofs, we can expect those who live in colder climates to experience higher MTBFs and those who live in hotter climates to experience lower MTBFs, just like we see with our LEAFs.
If you have any other type of system, you can make a similar type of calculation to estimate the MTBF of your system.