Inverter maker offered customer €50 for replacement product which would have carried ‘thousands of euros’ of associated costs


When a 1 MW plant operational since 2011 in southern Germany changed hands three years after installation, the new owner knew about the weak point of the inverters used so the problem was priced in. However, the project owner had not anticipated that weakness would become as annoying as it eventually did.

The majority of the 40 or so inverters on the project had already failed, one after another, and those which had not would malfunction at some point. That much was already known. The manufacturer knew the cause and, as long as there was a warranty, would replace the devices with repaired models. That seems reasonable even if the manufacturer insisted on replacing one unit at a time as failures occurred, rather than overhauling the lot.

Just wait four months!

Last year, when solar irradiation rose, two devices again failed but the project owner received an email from the inverter manufacturer stating no replacements would be available for at least four months. “Even though we paid extra for the warranty extension which was still valid” said the infuriated project owner.

What are your thoughts?

What is your assessment? Is this an isolated case? Which inverter topics you are most interested in, and do you also have experiences and cases to report which we can discuss at our quality roundtable at Intersolar in Munich, and from which the industry can learn?

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“Alternatively, we were offered the option of switching to an incompatible device,” he added. The wiring for the solar park would have had to be completely rebuilt to make that offer feasible. “Our maintenance company estimates that this would have cost several thousand euros,” said the project owner. The manufacturer had offered a flat rate of €50 for the “additional commissioning costs due to compatibility problems”.

The PV project owner instead sourced a used inverter of the same type, paid for it himself and cancelled his warranty extension. The manufacturer then moved and, a few weeks later, offered to deliver two devices from his old stock. It was subsequently agreed the warranty extension would not be cancelled and the costs of the replacement device purchased would be deducted from the annual invoice for the warranty. “That was a purely economic estimate”, said the owner, pointing out the manufacturer can expect to end up earning more from the annual warranty payments than the replacement equipment will have cost him.

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  • Assessing the quality of glass-glass modules
  • Lessons learnt from poor cable and connector quality
  • Examining inverter after-sales service and performance

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The story, however, was not over. The subsequent warranty bill arrived in full. “Several emails and telephone calls were necessary to finally receive the credit for the old device that we purchased ourselves,” said the project owner. Mainly because of poor internal communication at the manufacturer, he suspected. The lesson he derived from the episode was to buy cheap replacement devices on the secondary market.

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Expectations of service and insurance

However, buying used devices has become more difficult for new inverters, says our beleaguered project owner, as new models are more complicated than the previous generation. Interfaces have to be examined to determine whether replacements are compatible.

Nevertheless, the experience has not deterred our man from solar. In his experience, such serial equipment faults are rare. For loss of earnings, he has an all-risks insurance policy but certain insurance products can be expensive, particularly if mandated as part of bank financing. Negotiation is critical.

The project owner is, unsurprisingly, far more critical of inverter-specific insurance, and said in cases of multiple failures such policies often terminate or at least involve hiked premiums. For “normal wear and tear, they don’t pay”, he added. Insurance companies may send out assessors to question claims, even if – as in a case he experienced – the ‘expert’ was from an unrelated field. Such visits mean “you first have to pay €3,000 to keep up”, says our disgruntled project owner.

Our man said he should have been entitled to expect better service from an inverter manufacturer. The ‘hotline’ should have had a response in 3-5 minutes, not after half an hour in a telephone loop. The project owner cited how the car industry usually deals with serial failures. “There is a callback,” he said. Legally, replacements only have to be free of charge within a warranty period but manufacturers will usually bear the costs for some time after – the ‘dieselgate’ responses being a notable exception – in order to protect their brand.

Inverter customers generally assume the product will outlive a five or ten-year guarantee period, and a known manufacturer’s fault should also not be the reason for a failure after that time. After all, why should a customer have to pay for a warranty extension to get a known fault addressed?

(Field report recorded and written down by Michael Fuhs)

For discussion at the pv magazine quality roundtable at Intersolar Europe, May 2019:

  • Is this an isolated case?
  • What expectations about manufacturer service are fair and justified?
  • Is lack of compensation for lost revenue justifiable?
  • How can customers get an idea of service standards before buying an inverter?
  • The price pressure on inverter makers is high. How much does “satisfactory” service cost and would customers pay for it?
  • What types of insurance best protect customers against such cases?

Which inverter topics are of most interest to you? Do you have an experience to report from which the industry can learn?

Write to (we treat your information confidentially):  

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