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The Lifespan and Performance of Solar Panels

One persistent myth about alternative energy is that solar panel degradation makes solar installations uneconomical. Like lots of myths, there is a kernel of truth to this criticism. Solar panels do, in fact, degrade over their lifespan. But, the rate at which they degrade tends to be so small that even at the end of their (typically) 25-year warranty period, quality panels still produce 80-90% of their rated power. General industry consensus is that high quality solar modules will continue producing useful power for 40 or more years.

In this article, we discuss the factors that contribute to solar panel degradation, how they can be mitigated, and why, despite degradation, investing in solar panels still makes good economic sense for mid-Atlantic homeowners even when financed with a low interest loan.

Why do Solar Panels Degrade?

Solar cells, typically made primarily of silicon, generate electricity when photons from the sun are absorbed by the solar cell material, causing electrons in the cell material’s atoms to move between quantum energy states. One of the key benefits of solar power over other forms of energy generation (both fossil and renewable) is that panels of solar cells don’t have moving parts. It’s not over-simplifying to say that all you need to do to generate electricity with a solar panel is point it at the sun. There are no gears to maintain, no engines to tune. The system is, by and large, completely passive.

That upside comes with a downside, however. As anyone who has ever left patio furniture outside for a whole year knows, the elements are not kind or gentle. The static, passive nature of their operation is also the long-term Achilles heel of solar panels. To operate predictably and consistently, they have to endure rain, wind, debris, and temperature fluctuations. Of course, the real elephant in the room is the sun itself, beating down on the panels every day.

As this article from explains, virtually all the ways solar cells can fail (“failure modes”) relate to moisture incursion into panels and stresses on panels from temperature fluctuations. These failure modes are, by and large, unavoidable. Rain will fall and dew will collect on solar panels, and that moisture will eventually find its way into even the most well-constructed solar installation, causing corrosion and material breakdown that inhibits both generation and flow of electricity. And, even in the most temperate climates, panels that are intentionally oriented to capture maximum direct sunlight will experience wide swings in temperatures from day to night, causing deformation and warping over time, which can not only damage electricity-generating materials but will also tend to accelerate incursion of moisture, causing more corrosion, and so on.

How Fast do Solar Panels Degrade?

Fortunately, well-constructed, quality solar panels do not degrade very fast. In 2012, the National Renewable Energy Laboratory (“NREL”) published a comprehensive review of solar cell degradation rate studies over the past forty years finding that the median rate of performance loss for solar cells was 0.5% per year, and the average was 0.8% per year. The vast majority of reported degradation rate studies showed a decline of less than 1% per year. Although the study noted some variation among different solar cell technologies and climates, given the long-term nature of the study and the pace of improvement and evolution of solar products, it is safe to assume that a quality solar panel installation in the mid-Atlantic area will degrade between 0.5% and 1% per year.

The NREL study also makes the important distinction between degradation and “failure” of solar cells. Solar panel warranties usually guarantee that a panel won’t degrade below 80% of rated power by the end of the warranty period. But, that doesn’t mean solar panels that produce below 80% of rated power will be unusable. Quite the contrary, a highly efficient solar array may deliver ample electricity generation even at 50% of rated power. Before installing a solar array at your home, we can help you calculate your expected long-term energy needs and the amount of degradation a system could experience before it needed replacing.

How Can Solar Panel Degradation be Slowed?

At this time, there’s no practical way to shield solar panels completely from the vicissitudes of weather and climate. But, there are some things you can do to help maintain the output from your solar installation. First, it’s important to choose the right panels for your site, and the right installer for the job. As this article from Solar Power World observes, not all solar panels are made the same, nor are all solar installers equally careful about avoiding the sort of mistakes that can accelerate a decline in energy output. At Mountain View Solar, we have the experience and track record to help you select the appropriate solar panels for your location and to install them with the care necessary to ensure their long-term productivity.

Next, some basic maintenance can go a long way to eliminate conditions that will obviously hurt solar cell performance. Remove debris and dust from solar panels. They reduce the amount of light that can be converted and can work their way into the tightest of seals, hastening corrosion. Cut back tree branches that may both shade the panels and become damaging debris in a wind storm. And, if you clean dust from your panels with a garden hose, do so on a day when any excess moisture will quickly evaporate instead of seeping into seams. These measures won’t stop your solar panels from degrading, but they will help ensure that you aren’t speeding up the process. That said, however, solar modules are largely maintenance free and even without manual cleaning are expected to last decades.

Does Degradation Make Solar Panels Uneconomical?

Absolutely not. The economic calculation of whether it makes sense to install quality solar panels takes degradation into account. In our experience, a solar panel installation from Mountain View Solar takes 10 to 12 years to pay for itself in energy cost savings and credits. That’s only half as long as the typical warranted life of the solar panels we sell, and only about a quarter of their expected useful life. So, while it’s true that all solar panels currently sold will suffer a decline in output, they will have produced decades of essentially “free” energy before they need replacement. 25-40 years from now, solar modules will be magnitudes more powerful and efficient, and less expensive. That said, it’s like buying a car; you’ll use it for a period of time and then upgrade down the road. Unlike a car, your solar modules will pay for themselves and beyond even if replaced every 25 years, putting more money in your pocket.

Mountain View Solar sells top quality solar panels expected to produce adequate electricity for your home long after they pay for themselves. Contact us today to start a conversation about selecting solar equipment for your home that will produce power, and pay dividends, for decades to come.

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