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Thirty years later, old-school solar panels are still delivering on their promise.
In the late 1980s, when Switzerland was just beginning to experiment with solar power, engineers bolted a few shiny panels onto rooftops, mountain stations, and even utility-scale farms. They probably didn’t expect those panels to still be humming along more than three decades later.
But that’s exactly what a recent study shows. Researchers from Switzerland, Austria, and Germany tracked six photovoltaic systems installed between 1987 and 1993 across the country’s dramatically different climates — temperate valleys, snowy mountain huts, and high-altitude research stations perched above the clouds. After more than 30 years, those panels are still reliably producing electricity.
And now, research involving more than a million solar installations in Germany, alongside decades-old panels in the Algerian desert, reveals something even more interesting: solar power can be remarkably durable, though not all panels age the same.
On average, the Swiss systems lost just 0.24% of their performance each year. That’s about three times slower than what’s often reported in the literature. Laboratory tests showed that most of the individual panels still delivered more than 80% of their original rated power after 30 to 35 years — well past the 25-to-30-year warranties manufacturers usually provide.
“This [data] really shows that photovoltaics can last [longer than expected], and it’s an important message to the photovoltaic industry,” lead researcher Ebrar Özkalay at the University of Applied Sciences and Arts of Southern Switzerland, told Chemistry World.
The results are very similar to findings from France last year. There, Hespul, a renewable energy nonprofit, tested the country’s oldest rooftop solar system, installed in 1992. After 31 years, the French panels were still operating at nearly 80% of their original capacity — right in line with the Swiss data. Hespul declared that the results demonstrated photovoltaics’ “capacity to become one of the major sources of energy in France and in the world.”
Together, these studies show that solar panels, even those using outdated tech from decades ago, can keep running for a very long time.
But how representative are these remarkable survivors?
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In 2026, researchers from Germany’s Brandenburg University of Technology Cottbus-Senftenberg and Imperial College London published one of the largest real-world investigations of solar panel ageing ever conducted.
Instead of examining a handful of decades-old installations, they analysed production records from 1.25 million German photovoltaic systems, covering 34 gigawatts of installed capacity and up to 16 years of operation.
The results were reassuring.
On average, the systems lost about 0.59% of their output annually. That’s higher than what the Swiss study found, but still substantially less than many previous estimates. And the rate of decline appeared to slow with age. By their tenth year, installations were losing output 7% to 13% more slowly than when they were new.
Not all installations performed equally well, however. Larger systems, those above 30 kilowatts of peak capacity, experienced roughly one-third faster degradation than smaller systems. Extreme temperatures and particulate air pollution also contributed to reduced performance.
The findings strengthen the argument that solar power is a long-term investment, rather than technology destined for replacement the moment its warranty expires.
But in some places, panels might suffer a bit more.
In another study published in 2026, researchers in Algeria examined 64 monocrystalline solar panels manufactured by Arco Solar in the early 1980s. These panels had endured a very different life from their Swiss counterparts.
They spent approximately 20 years operating in the hot, dry climate of southwestern Algeria. Later, they were moved to a coastal research facility, where they operated for another five years before remaining outdoors, disconnected from a load, for a further five years.
After three decades of outdoor exposure, the panels retained an average of approximately 53% of their original rated power. Some performed much worse, while the best retained nearly 69%. Their estimated annual degradation rates ranged from 1% to 2%.
Researchers documented discoloration, cracked cells and detached electrical junction boxes. Although the tested modules passed dry insulation-resistance testing, only 63% passed the wet-leakage test, raising concerns about electrical safety under moisture exposure.
A separate 2026 investigation in Chile’s Atacama Desert, analysing 1,216 solar modules after ten years of exposure, estimated degradation at 1.32% annually. Its projected lifespan to the 80% power threshold was only about 15 years under baseline assumptions, although estimates varied considerably depending on assumptions about the modules’ initial power.
This doesn’t necessarily mean that all deserts will kill solar panels, but it does suggest that panels in different places can age quite differently.
The Swiss study dug into why some panels age better than others. Location turned out to matter. Panels in low-altitude towns, where surfaces can heat up to 80°C in summer, degraded faster. The constant heating and cooling cycles stressed the materials, leading to local corrosion and reduced conductivity.
By contrast, panels mounted in alpine environments weathered the cold surprisingly well. They faced high ultraviolet radiation and wild day–night swings, but they generally retained performance better than their lowland counterparts.
Even more important than climate was what the researchers called the “bill of materials.” Panels built with robust encapsulants, adhesives, and backsheet laminates lasted far longer. Those early 1990s modules used tough EVA encapsulants, Tedlar backsheets, and solid glass/foil structures. Some variants, like Siemens’ SM55-HO “high output” panels, even had different filler materials in the laminate to boost efficiency, which influenced how they aged.
Not every panel held up equally. The oldest models, manufactured before UV stabilizers were added to encapsulants, showed more discoloration and delamination. Others suffered from solder bond failures that cut efficiency. Still, the fact that most continued to perform at a high level after decades in the field is remarkable.
The subsequent German, Algerian and Chilean findings reinforce that larger point. Temperature, materials and the design of an installation can influence how quickly it deteriorates. But they also suggest that an exceptional result from one group of panels should not be mistaken for a universal rule.
Today, solar is no longer a boutique experiment. It supplied approximately 8.7% of the world’s electricity in 2025, according to Ember, while the International Energy Agency estimates that solar accounted for 75% of all new renewable electricity capacity added that year. As we enter what researchers call the “terawatt age” of photovoltaics, the long-term reliability of solar panels matters more than ever.
The Swiss findings suggest that cutting corners to boost efficiency or lower costs could be a mistake. “The bill of materials — everything that goes into a panel — has a great influence on performance, even when made by the same company,” notes Dirk Jordan, a photovoltaics expert at the U.S. National Renewable Energy Laboratory.
Modern modules are often designed with thinner, cheaper materials. That may drive down upfront prices, but it risks compromising longevity. The Swiss researchers raised this as a potential trade-off, not proof that modern panels generally age faster than their predecessors. Newer technologies have also benefited from improvements in manufacturing, testing and materials. Their long-term field performance will take decades to establish with the same confidence.
The old-school panels remind us that durability is just as crucial as efficiency and upfront cost in making solar sustainable. Longer-lived panels mean fewer replacements, lower costs, and a smaller carbon footprint.
The real question is no longer simply whether solar panels can survive for decades. It’s how to make sure more of them do — without sacrificing too much power along the way.
The original findings appeared in the journal EES Solar.
Transparency note: As part of ZME Science’s effort to revisit science stories and follow how the evidence develops, we have revisited this article, originally published in August 2025. The proposed update adds research from Germany, Algeria and Chile examining the long-term degradation of solar installations, updates global solar-energy statistics, and clarifies how climate, construction and electrical safety influence the useful lifespan of solar panels. The original Swiss findings remain valid, but the additional evidence shows that not all installations retain their performance equally well.
Tibi is a science journalist and co-founder of ZME Science. He writes mainly about emerging tech, physics, climate, and space. In his spare time, Tibi likes to make weird music on his computer and groom felines. He has a B.Sc in mechanical engineering and an M.Sc in renewable energy systems.
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© 2007-2025 ZME Science – Not exactly rocket science. All Rights Reserved.
