Schott Solar AG, the German solar panel manufacturer, will extend guarantee conditions for two of its photovoltaic module lines. As reported by Renewable Energy World, the group will now offer a “25-year performance guarantee on glass-foil modules and a 30-year guarantee on double glass modules.” Earlier this month, Schott announced its plans to raise the warranty to 25 years on its line of POLY panels:

“This warranty extension further reinforces SCHOTT Solar’s position as a high quality manufacturer of photovoltaic modules,” said Mark Finocchario, President and CEO of SCHOTT Solar. “We are able offer our customers a 25-year performance warranty because of our strict manufacturing controls. Independent tests have proven time and again the excellent longevity and performance stability of SCHOTT Solar’s quality modules.”

When it comes to solar PV, product warranties are particularly important for a number of reasons. First, all solar panels slowly degrade over time. A 220-watt panel today, for instance, inevitably produces less electricity that it will 15 or 20 years down the line. While such degradation is slow — and while some panels manufactured in the 1970s are still putting out power — manufacturers offer decades-long warranties to reassure the buyer that their products will perform as advertised. A typical warranty in the industry guarantees that a panel will produce electricity for 10 years at 90 percent of its rated power output, and for 20 years at 80 percent of its rated power output.

Second, in order to function, panels must be outside — which means that they’re exposed to nature’s elements. The quality of a panel’s glazing and casing are important considerations, and are usually included in warranty provisions. Be sure to read the details, however — some panel makers limit coverage if the panels are placed in unusually harsh conditions, like marine environments.

Finally, while interest has grown in recent years, solar PV has yet to hit the mainstream. Potential buyers have a lot of questions and, in some instances, concerns. To be successful, manufacturers of PV equipment must back their products. End of story. Interestingly, there’s been something of a herd effect within the industry: one manufacturer raising the warranty bar increases pressure on all others to do so as well. We’ll see if Schott’s recent moves contribute to this trend.

Stay tuned. Next time I’ll be writing about rated power output and output tolerance. Fun stuff!