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Researchers in Switzerland have been keeping an eye on a bunch of old solar inverters and power optimizers to see how they are faring; with some interesting results.
Solar panels tend to steal the limelight, but the real workhorse of a PV system is the solar inverter. This device takes all the DC output of the panels and converts it to AC for use in the home and export to the grid. It carries out this task day-in, day-out under all sorts of challenging environmental conditions.
As it’s the component under the most strain, the inverter is also the one most likely to fail first. Buying cheaper good quality solar panels is fine, but cutting corners on inverter quality can lead to disappointment down the track.
While 25 year product warranties for solar panels are becoming increasingly common at the cheaper end of the spectrum, standard inverter warranties tend to be far less generous even among the top-end brands. For example, a top quality inverter brand is Fronius; but Fronius inverters only come with a 10 year product warranty (5 years full + 5 years parts only).
So, how long do inverters last generally?
Boffins at Switzerland’s Bern University of Applied Sciences have been seeking an answer to this question.
Their research incorporates 1,195 PV systems consisting of 2,121 inverters and 8,542 optimizers installed in Switzerland. An optimizer is a type of Module Level Power Electronics (MLPE), aka Panel Level Optimisation (PLO), device added to one or multiple solar panels in a system to maximise panel output. These devices are used in addition to a string inverter. Not all systems in this study have optimizers.
Most of the inverters part of this research were from the following brands:
With Fronius, SMA, SolarEdge and Huawei inverters among the most common, it was going to be a case of a rising tide lifting all boats. As for Kostal and Sputnik inverters, this is the first I’ve heard of them.
In a nutshell, what the researchers have determined so far is 65% of the inverters will not have a yield-relevant fault by their 15th year of operation. Furthermore, some inverters may have been replaced while they were still functioning properly; e.g., when a system was upgraded. In this study, such a scenario counted as an inverter failure.
Among their conclusions, the researchers noted time-to-failure (TTF) was dependent on various factors aside from general manufacturer quality1. For example, outdoor installations had a shorter TTF than those installed indoors2.
Another interesting finding was in systems where power optimizers were used, the first fault generally occurs earlier than in PV systems without power optimizers – so some failures were likely not inverter-related per se. While optimizer warranties tend to be significantly longer than inverters, in the case of a failure it needs to be replaced and that’s a hassle. The study mentions overall reliability of a PV system increases significantly with a reduction in the number of power electronic components.
The oldest inverters in the study are from the early 1990s, but most were commissioned between 2008 and 2013. 2008 is ancient history when it comes to solar power3, and inverter/optimizer technology has evolved since then4.
The study certainly has its limitations, but it indicates if you choose a good quality inverter, it should last well beyond the product warranty period.
A copy of the study – “Life Expectancy of PV Inverters and Optimizers in Residential PV Systems” – can be requested here. We had to ask, so you do too; lest we are berated by Swiss researchers .
Related: Help! My Vintage Solar Inverter Has Finally Failed.
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