have become innovative at improving solar panel efficiency and durability. Solar panels need to be able to resist extreme weather such as harsh wind and heavy rainfall. In most cases, they are rigorously tested and even certified to withstand hailstones up to two inches in diameter (or larger) falling at 50 miles per hour.
The National Renewable Energy Laboratory (NREL) campus in Golden, Colorado was put to an unexpected test when a severe hailstorm hit the area in May 2017. The storm left a trail of destruction in its path, leaving tennis ball-sized dents in the roofs and damaging hundreds of cars .
After the storm, the campus employees set out to assess the damage of the laboratory’s solar array. Of the more than 3,000 panels on the roof of this net-zero energy building, only one panel sustained some damage. This is a great example of the ability of solar panels to withstand strong physical impacts .
Such exceptional resilience makes emerging solar technology promising as a reliable power supply for our homes. Solar panels will offset your energy use for a very long time without requiring much maintenance. However, being exposed to the elements day in and day out will decrease their efficiency in the long run.
Here’s a breakdown of important things you need to know about solar panel lifespan and what causes their degradation.
What is the life expectancy of a solar panel?
Compared with other appliances, solar panels actually have a long life expectancy. Most panels come with warranties assuring 80 percent system performance or higher for up to 25 years.
This doesn’t mean your solar panels need to be replaced after this period; even after the warranty period, the majority of panels continue to produce electricity but with less efficiency. Although, as time passes (and solar panels age), we get real-life proofs of a much longer average lifespan due to solar panels’ outstanding durability.
One of the oldest solar panel installations can be found in Germany on the building of the University of Oldenburg. To the surprise of researchers, their “experimental” solar array installed on the roof in 1976 is still producing energy with a minimum variation of the original output. Similar evidence of reliable performance is documented on the Kyocera array from 1984 in Stockholm .
Such examples have appeared more and more frequently in recent years. And many solar energy proponents claim that solar panels can perform for over 40 years ! But before you pop that champagne in celebration of a good investment, it is good to know that the longevity of your solar panel is affected by many factors, including weather patterns or the quality of the material.
Solar Panel Performance Over Time
What most interests every solar owner is the power decline over time of solar panels, commonly referred to as “solar panel degradation rate.” Over years of continuous exposure to changing weather, solar cells begin to wear down and produce less and less power.
According to a study carried out by the National Renewable Energy Laboratory (NREL) in 2012, solar cells lose, on average, about 0.5 percent of efficiency per year. This means that after 20 years, a solar panel will perform at 90 percent efficiency, which is reflected in the power output of the whole solar system.
For example: A twenty-year-old 5 kW system will equate in terms of the energy output to a 4.5 kW system.
You probably will not notice the difference at first, but after 30 to 40 years, this will make a big dent in the amount of energy the system will produce.
Why do solar panels degrade, and what causes solar panel degradation?
Although solar panels are very resistant, we cannot expect three-decades-old arrays to perform as well as they did when they were brand new.
There are three main factors affecting the performance of all photovoltaic modules:
- Varying levels of water vapor in the air
- Exposure to UV rays
- Mechanical damage
This means that solar panels placed in cold climates with heavy precipitation (in the form of rain or snow) or in countries closer to the equator with high UV index, are vulnerable to faster degradation rates than those in moderate climates. This happens because the material must withstand tough conditions for longer periods of time.
Even though some panels wear down more quickly than others, time will eventually take its toll on all of them. The most common signs of degradation that affect how long will solar panels last are:
- Loosen frame
- Deterioration of anti-reflective coating
- Short-circuited solar cells at corroded or damaged spots
- Cracked cells 
Whether you will encounter one or more of these problems depends greatly on the resistance of your solar panels’ construction materials. Unfortunately, many models are still prone to manufacture failures, which speed up the degradation within the cells and shorten life of solar panels.
Some common problems arising from the low-quality production include:
- The absence of UV-blockers in encapsulation foil, leading to quicker discoloration and backsheet degradation
- Solar cells having micro-cracks, which are not visible to the naked eye but affect the output of the panel instantly by blocking incoming sunlight 
- Latent cracks of solar cells, which only appear after some time of usage but were caused during processing 
- Thinner frames to reduce the amount of aluminum in production, which bends when snow puts pressure on some parts and can damage solar cells 
Based on the severity of the defect, you might have to replace your array prematurely (even within the warranty period).
In any case, make sure you choose a verified solar company with great customer service. It will save you a lot of trouble when dealing with any problems.
What happens to old solar panels?
Most countries have not developed a recycling strategy for discarded solar panels yet. Considering the lifespan of solar panels, the technology is still fairly new, and the number of old panels reaching waste facilities remains too low to warrant special treatment.
This “quiet” state will not last much longer, as the amount of discarded solar panels worldwide is expected to rise to 78 million tons by 2050. For a more accurate approximation, it is estimated that the number of solar panels going to waste will roughly equal the number of new installations .
Such numbers can no longer be neglected. Old solar panels will soon represent a significant portion of the world’s electronic waste, which contains many precious materials well-suited for reuse. For example, most crystalline silicon modules are made of easily recyclable materials such as glass and aluminum.
A nonprofit organization, PV CYCLE, based in Europe, offers the first recycling program of all types of photovoltaic technologies . According to an announcement last year, they have achieved a 96 percent recycling rate of silicon-based solar panels. This is important achievement because efficient recycling strategy is the key to minimizing the environmental footprint of the solar industry.
Europe is also the birthplace of strict solar waste regulation—the Directive on Waste Electrical & Electronic Equipment (WEEE). The Directive dictates the “Extended Producer Responsibility,” where producers must take panels back from customers and recycle them free of charge. This strategy aims primarily to reduce the demand for more natural resources .
Other countries (including the United States) classify solar panels as general or industrial waste, which has to be tested for hazardous contents and disposed according to country’s regulations. Given the high recycling rate of solar panels, these practices are wasteful.
If other countries adopted the same recycling scheme as Europe, the amount of globally recovered material would be immense. According to the report from the International Renewable Energy Agency, the value of materials recovered from all old photovoltaic systems would reach an unbelievable USD 450 million in the next 13 years . So the argument that the cost of recycling is too high is losing its validity as time passes and more solar panels enter our waste stream.