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What Determines The Lifespan Of Solar Panels?

Posted by Kyle Pennell, Guest Columnist

Jan 5, 2018 5:50:25 PM

Solar panels don’t last forever. But what determines when and why solar panels die?

The truth is that solar panels don’t typically die in the traditional sense. That is, they remain operational decades after they’re installed, but not as well as they did back when they were new. The slow decline in the panels’ energy-generation capability is known as its degradation rate. When panels produce less than 80 percent of the energy they did when they were new, they’re considered failed, and most solar installers will recommend that they be replaced.

Since all manufacturers make their panels slightly differently, degradation rates vary. The National Renewable Energy Laboratory has found that panels typically degrade at a rate of 0.8 percent annually. In other words, after one year, your panels will be 99.2 percent as efficient as they were when they were first installed. After 10 years, the panels will produce 92 percent as much energy as they did when they were new. Panels made today can achieve degradation rates as low as 0.3 percent per year, though you’ll pay more for panels with lower degradation rates. Some panels remain productive long after their typical 20 to 25 year warranty period expires, even if they have average degradation rates.

solar panel

The degradation rate is partly determined by the type and quality of a panel’s solar cells. Solar cells are at the heart of every solar panel, and convert the sun’s light into usable electricity. Crystalline silicon cells tend to degrade at about 0.5 percent annually, while thin-film solar cells tend to degrade at rates closer to 1 percent each year (though advances in thin-film cell technology have led to steady drops in their degradation rates).

Location is another major factor that can affect your panels’ lifespan. If you’re located in a temperate zone, your panels will likely last longer than they will at a higher latitude, where seasonal expansion and contraction can cause stress and introduce microcracks. Panels that have to bear a snow load might also have some years shaved off their life, since snow can bend the frame that surrounds the panel, exposing the panel’s internal components to moisture and ice and, in some cases, dislodging the panels from the frame entirely. Ice and snow can also loosen or bend the mounts that hold the panels, increasing the likelihood that the panels themselves will be damaged.

At the other end of the temperature spectrum, panels that are constantly hot also pose a problem. Panels are tested under a standard temperature of 25 degrees Celsius and expected to operate at or below that temperature. Temperatures over 25 degrees will accelerate panel degradation. Other weather conditions like hail (which can cause cells to crack) and humidity (which can cause panel corrosion) also threaten panel longevity.

Other design choices like the inclusion of premium trim can add years to the useful life of your solar panels. This trim can prevent the introduction of water vapor and other contaminants that can lead to corrosion and make it harder for the solar cell within the panel to transmit energy. For the same reason, panel failure rates are lower when electrical insulation, thermal insulation, and other moisture barriers are laminated together within the panel. Another feature that affects panel lifespans is the antireflective coating. A high-quality anti-reflective coating protects the solar cell and increases its efficiency.

Other issues begin with the panels’ processing and assembly. In some instances, panels are manufactured with “latent cracks” that are imperceptible during the initial quality control and shipment phases, but appear after installation. Impurities in the laminates that are used to bind the cell can lead to cell corrosion. And like all electronics, solar cells are vulnerable to short-circuiting at cell interconnections-a phenomenon that is more common in thin-film cells than in their crystalline silicon counterparts.

Improper installation, additionally, can shorten the panels’ lifespan. This could mean that the panels aren’t connected correctly or that they’re damaged during installation. Typically, the bigger failure issue with most solar installations is not the panels themselves, but the inverters. Central and string inverters (which comprise 96 percent of all inverters in use today) need to be replaced every 10 to 15 years. (Microinverters, on the other hand, have lifespans comparable to most solar panels.)

Unless you pick up and move to a more temperate location, there’s little that can be done to extend the life of your solar panel. The panels themselves have no moving parts. Removing leaves, snow, and other debris is usually recommended. But the best thing you can do to ensure your panels produce clean, free solar energy for decades to come is to choose a trusted installer and a reputable panel manufacturer.

Kyle Pennell is the Content Manager at PowerScout -- we help homeowners figure out if installing solar is right for them and get competitive bids from multiple installers.

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