How Long Does an Inverter Last?
You probably know that solar panels are designed to last at least 25 years on your roof, but what about the other crucial component of your solar power system—the inverter? There are different claims about the expected lifespan of inverters and optimizers. For example, the website milieucentraal.nl states: "A central inverter needs to be replaced after about 12 years," while "micro-inverters can last up to 25 years." Meanwhile, SMA claims on their FAQ page that their inverters are designed to function without issues for at least 20 years. Nice claims, but what can actually be proven about how long inverters and optimizers last?
A recent study by a Swiss university investigated the lifespan of inverters. The results are not yet final, but they already provide some interesting insights. The study examined 1,280 PV installations with string inverters or optimizer-based systems.
Indoors vs. Outdoors
The first conclusion is that inverters generally last quite a long time: after 15 years, more than half were still working just fine. However, there were some differences between the brands studied. The research did not disclose which brand performed best or worst, but for the top-performing brand in the study, 70% of the devices were still operating normally after 18 years.
It also mattered whether the inverters were installed indoors or outdoors: inverters installed indoors showed fewer failures than those placed outside. This makes sense since outdoor inverters are exposed to the elements and temperature fluctuations. At Zonnefabriek, we only install inverters outdoors when there’s no suitable indoor location, and we always ensure they are protected from direct sunlight.
More Components, More Potential Failures
Additionally, smaller inverters with less power (below 5 kW) tended to last longer than larger ones (above 20 kW). Another interesting finding: while the failure rate of an individual optimizer was relatively low, optimizer-based systems (such as those from SolarEdge) have an optimizer behind each panel. The more optimizers, the higher the likelihood of a malfunction. In systems with 20 optimizers, about 20% experienced an optimizer failure after 10 years—excluding any issues with the associated inverter.
What About Zonnefabriek’s Inverters?
The Swiss study is insightful, but Zonnefabriek can also draw from its own extensive experience to determine the lifespan of the inverters we've installed. Founded in 2009, Zonnefabriek started installing significant volumes in 2011. We analyzed all inverters we installed in 2011 to see how many had failed in the past 10 to 11 years.
In 2011, we almost exclusively installed SMA inverters, particularly smaller models like the Sunny Boy 2100TL (often part of the 'ZonVast' initiative from energy provider GreenChoice). Out of the 250 SMA inverters we installed that year, we found that only three had failed! This means that after more than a decade of daily operation, an impressive 99% of the inverters are still functioning!
In 2011, we installed many of these models: the SMA Sunny Boy 2100TL.
German Reliability
We do have to make a small disclaimer: some failures might have gone unreported to us—perhaps because the customer didn’t notice or because they chose another installer for repairs without telling us. However, it seems unlikely that the inicidence of such cases would be significant. We can cautiously conclude that the German reliability SMA promises is indeed supported by the data. That’s also one of the reasons why Zonnefabriek chooses SMA inverters for our leasing projects (where we remain the system owners and bear the cost of any failures).
We hope that the systems installed in 2011 will continue to operate smoothly for another 10 years. Are you as curious as we are? Let’s check back in 2032—stay tuned to our website!
