Solar Panel Degradation Ranges From 0.24% to 2% a Year

Estimated reading time: 7 minutes · Last updated: 14 November 2026

Solar panel degradation is far slower in some places than others. Six Swiss photovoltaic systems installed between 1987 and 1993 lost just 0.24% of performance a year, and most of their panels still produced more than 80% of rated power after 30 to 35 years. In southwestern Algeria, 64 Arco Solar panels from the early 1980s kept only about 53% after three decades, with yearly losses of 1% to 2%. A 2026 analysis of 1.25 million German systems landed between them, at about 0.59% a year. The gap comes down to heat, pollution, system size and, above all, what the panels are made of. With solar supplying 8.7% of global electricity in 2025, that variation matters.

The bill of materials — everything that goes into a panel — has a great influence on performance, even when made by the same company

Dirk Jordan, photovoltaics expert, U.S. National Renewable Energy Laboratory

Why Swiss Panels From the Late 1980s Still Work

Researchers from Switzerland, Austria and Germany followed six photovoltaic systems installed between 1987 and 1993. The sites ranged from temperate valleys to snowbound mountain huts and research stations high above the clouds. Every one of them still generates electricity after more than 30 years.

Averaged across the six, output fell 0.24% a year, roughly a third of the rate often cited in published research. Lab tests found most individual modules still delivering more than 80% of rated power after 30 to 35 years, beyond the 25-to-30-year warranties manufacturers typically offer.

Lead researcher Ebrar Özkalay of the University of Applied Sciences and Arts of Southern Switzerland said the data shows photovoltaics can outlast expectations, a message Özkalay called important for the industry.

France points the same way. The nonprofit Hespul tested a rooftop system installed in 1992 and found it running at nearly 80% of original capacity after 31 years, which Hespul said showed photovoltaics' "capacity to become one of the major sources of energy in France and in the world."

What 1.25 Million German Systems Reveal About Ageing

In 2026, a team from Germany's Brandenburg University of Technology Cottbus-Senftenberg and Imperial College London went far broader. Instead of a few veterans, they worked through output data for 1.25 million photovoltaic systems in Germany, totalling 34 gigawatts, some with as many as 16 years of operation.

Degradation is the gradual loss of a panel's ability to convert sunlight into electricity, usually expressed as a percentage of output lost each year. Across the German fleet it averaged about 0.59% annually, above the Swiss rate but below many earlier estimates. The decline also slowed with age: by year ten, the annual rate of loss had eased by 7% to 13% compared with the early years.

Size made a difference. Systems above 30 kilowatts of peak capacity degraded roughly one-third faster than smaller ones, and extreme temperatures and particulate air pollution also dragged performance down.

How Desert Heat Cut Algerian Panels to About Half Power

Another 2026 study examined 64 monocrystalline panels made by Arco Solar in the early 1980s. Their life was harsher: about 20 years in the hot, dry southwest of Algeria, five more at a coastal research facility, then five years outdoors with no load attached.

After three decades outside, the panels averaged about 53% of rated power. The best kept nearly 69%, some did far worse, and estimated yearly losses ran from 1% to 2%. Researchers recorded discoloration, cracked cells and junction boxes that had come loose. All tested modules passed a dry insulation-resistance check, yet only 63% passed the wet-leakage test, a concern for electrical safety when moisture is present.

In Chile's Atacama Desert, a 2026 study of 1,216 modules after ten years put degradation at 1.32% a year. Under baseline assumptions that implies only about 15 years to fall to 80% of rated power, though the figure moved considerably depending on what initial power was assumed.

Why Materials Mattered More Than Climate in Switzerland

The Swiss team also asked why some panels aged better than others. Altitude mattered. In low-lying towns, panel surfaces can hit 80°C in summer, and the repeated cycle of heating and cooling stressed materials, producing local corrosion and weaker conductivity. Alpine panels faced intense ultraviolet light and sharp day-night swings, yet generally kept their performance better.

Climate still ranked behind the bill of materials, meaning every component and substance that goes into a module. Modules whose encapsulants, adhesives and backsheet laminates were robust survived much longer. The early 1990s units paired EVA encapsulants with Tedlar backsheets in durable glass/foil builds, while Siemens' SM55-HO high-output panels used different laminate fillers to raise efficiency, which changed how they aged.

Weak points showed up too. The oldest designs, built before UV stabilisers went into encapsulants, had more discoloration and delamination, and some lost efficiency to solder bond failures.

Can Cheaper Modern Panels Match the Old Ones?

Ember puts solar's share of world electricity at about 8.7% in 2025, and the International Energy Agency estimates solar made up 75% of all new renewable capacity added that year. Researchers call this the terawatt age of photovoltaics, and at that scale each extra year of panel life carries real weight.

Dirk Jordan, a photovoltaics expert at the U.S. National Renewable Energy Laboratory, said: "The bill of materials — everything that goes into a panel — has a great influence on performance, even when made by the same company."

Many modern modules use thinner, cheaper materials, which trims upfront prices but may shorten their working lives. The Swiss researchers framed this as a possible trade-off rather than proof that today's panels age faster, and newer products also gain from better manufacturing, testing and materials. Field evidence on them will take decades to build.

How long solar panels will last

The bottom line

Three decades of data now tell a more nuanced story than the original Swiss result alone. Well-built panels in Switzerland lost 0.24% a year and mostly cleared 80% of rated output after 30 years. Germany's fleet averages about 0.59%, with big systems and hot, polluted sites faring worse. Panels in the Algerian and Atacama deserts lost power far faster, and the Algerian wet-leakage results turn an efficiency question into a safety one. Solar panels neither last forever nor fail on schedule when the warranty ends. Materials, climate and design set the pace, and today's thinner modules have yet to show which pattern they will follow.

What to watch

• Watch for long-term field data on modern modules built with thinner, cheaper materials, which the Swiss researchers say will take decades to establish; no date has been set.
• Watch for follow-up work on the wet-leakage failures found in the Algerian panels and what they mean for older desert installations; no date has been set.
• Watch for further analysis of the German fleet as its systems move past 16 years of operation; no date has been set.