SS#8: Do string inverters deserve more credit?

The findings: in the study, “more than 65% of the inverters did not present yield-relevant faults by year 15”.

Author

Sean Collier
February 11, 2023

Hello, welcome to Solar Saturday.

A recent article by PV Magazine piqued my interest in string inverter lifecycles (link to original article here). It comments on research by The Bern University of Applied Science in Switzerland. They have conducted a survey on the durability and performance of residential PV inverters and optimisers over a 15-year period.

The findings: in the study, “more than 65% of the inverters did not present yield-relevant faults by year 15”.

It’s often assumed in the industry that string inverters are likely to need replacing after 10-12 years. Many build this into calculations at the beginning of the project. I’m naturally a cautious guy when it comes to this, preferring to build in a potential replacement or two over the system life of 25-30 years.

But should we be giving string inverters more credit? What do you think?

The first boom of UK solar was in 2010/11. We should then be expecting to replace a lot of string inverters installed under Feed in tariffs in the next 1-3 years. Possibly it will be a bit longer than we all expect.

The survey covered 1,195 PV systems covering brands like Fronius, SMA, Huawei, Kostal, SolarEdge and Sputnik.

The data also suggested that outdoor installations showed a trend towards faster failure, and that Power Optimised systems showed a trend in which fault in the inverters earlier than non-optimised systems. The results from the research overall are broad and not controlled, meaning this can be anecdotal and perhaps not relevant to todays products in the market - it could be better or worse now as costs came down and volumes ramped.

I’m sure that some brands and quality levels will be different, even our climate in the UK is a differentiating factor over the research in Germany and Switzerland.

Nonetheless I think it raises interesting questions about how long a string inverter could last in the field.

I’d be interested to hear your views and experiences. Head over to this post on out LinkedIn page to comment, or email me: sean[at]solarcrowd.co.uk

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Enjoy the weekend!

Sean