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Solar panel degradation and how to slow it down
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Solar panel degradation and how to slow it down

15 mins 03 Feb 2021
Although solar panels are sturdy and reliable, they don't last forever — nothing does. Over the course of years panels tend to gradually lose their efficiency. This process is called solar panel degradation. How fast they lose their power, how long warranties last and what to do to prolong the lifespan of your solar system — here in this article.

Solar panels last for more than 25 years

An estimated lifespan of solar panels is around 25-30 years or even more. That's why top manufacturers provide warranties for up to 25 years. They guarantee not only that solar panels shouldn't break on their own during this time but also that their energy production won't drop below a certain level. A common estimation is that performance shouldn't drop below 90% of their maximum in the first 10 years and shouldn't be lower 80% in the next 10-15 years. If you want to know more about the lifespan of solar panels, check out our article on how long solar panels last.

Before putting solar panels on the market, manufacturers test them for performance and endurance. Solar panels withstand extreme weather conditions pretty well: according to data by National Renewable Energy Laboratory (NREL), only 0.1% of 50,000 solar panel systems were damaged or seriously affected by extreme winds or hurricanes between 2009 and 2013. They are made to endure hail at 23 meters per second or a wind at 140 mph. What makes solar panels so long-lasting and durable is the absence of moving parts. But it doesn't mean that they are invincible. Harsh weather and extreme temperatures slowly ruin the panels until eventually they produce little to no energy. What they cause are microcracks in the silicon which obstruct the flow of electricity. The sun itself destructs panels little by little: ultraviolet rays make a negative impact on the system efficiency. Some studies show that panels lose around 1-3% of efficiency right after installation as they become exposed to the sun and UV for the first time.Several hours later degradation rate slows down. Solar panels also don't like when parts of the solar panel system have different voltages.

Solar panels degrade by 0.5-0.8% every year

So what is the solar panel degradation rate? A while ago it was believed that every year the performance of solar panels goes down by 1% no matter what. The report from NREL published in 2012 shows that the average rate of degradation is closer to 0.8% with median value of degradation at 0.5% — experts have analysed nearly 2000 degradation rates based on reports published in 40 years. However, it's important to note that rates of degradation are not the same across all solar panels. The main factors that come into play are the area, where panels are installed, the year of manufacture and the brand.

First of all, engineers continue to modernise the design of solar panels and improve its longevity. Therefore the panels that are produced in the 21st century show lower degradation rates than those that were made before 2000. We're, however, already 20 years into the new millenium, so right now the oldest panels are approaching the end of their road anyways.

The highest rates of degradation show the panels installed in dry, hot, desert places where ultraviolet radiance becomes a big factor. Solar panels lose almost 1% of efficiency every year in these conditions. PV modules also degrade at similarly high rates when they are subjected to ice and snow loads in cold climates, but these rates become better if snow doesn't accumulate and slides off panels (or panels are cleaned regularly). Northern parts of the USA show the lowest degradation rates (around 0.2%) due to the moderate climate.However, northern states for the most part aren't the sunniest which means less energy produced.
Finally, before purchasing solar panels you have to carefully examine the list of manufacturers. Different brands have different strengths and advantages to their product. When it comes to longevity and lowest degradation rates, the most reliable brand is probably SunPower with LG and Panasonic following right after. All three brands issue a warranty for 25 years, which asserts that panels are going to give out more than 90% of their initial performance even at the end of the warranty (with SolarPower promising 94% of efficiency after 25 years).

Obviously, these rates of degradation apply primarily to monocrystalline and polycrystalline panels. However, there are also thin-film panels that are not taken into account. Usually, their lifespan is considerably shorter at around 10-15 years — but then again they are the cheapest on the market. It is fair to assume that they are more susceptible to extreme weather conditions as essentially it's just photovoltaic material applied onto glass or metal substrate.

Keep your solar panels clean and safe

To slow the rate of solar panels over time, it is best to have them inspected regularly by experts from the manufacturer or installer. Regular check-ups will prevent potential damage to panels in case of exposed wires or anything like that. Trying to fix such problems by yourself can result in damage to panels.
Which would be hard to compensate through the warranty. Consult with the manufacturer about best ways to keep your panels safe and efficient.
Solar panels are a relatively care-free investment but it's better to clean them every once in a while — the frequency depends on the area where you live. When panels are installed on the roof, rain more or less takes care of them, but eventually they'll need a proper cleaning anyway. When panels are on the ground, debris and dirt are much more of a nuisance and it's almost mandatory to clean them at least once a year or it results in a decrease of efficiency. Monitoring system lets you know when it's time for a scrub — if the efficiency of panels dropped, the dirt or fallen leaves are the most obvious reason. Again, solar panels don't like thick layers of snow on them — not only does it decrease the amount of sunlight they are able to receive at the given time, it increases the rate of degradation. If snow doesn't slide off the panels, you have to clean them yourself or call for a special service. If you want to learn more about cleaning solar panels, here is another article for you.

Keep in mind that while solar panels themselves last for a long time, other components of the system might want a replacement much sooner. An inverter, for example, can last for 10-15 years and the lifespan of some models can exceed 20 years. Solar charge controllers also work reliably for 15 years on average. The life of a battery, however, highly depends on its properties and maintenance, and might serve you from a decade to several months.

Solar panels don't stop after 25 years

Solar panels do not just immediately break after 25 years have passed and the warranty for them has run out. The only difference is that you can't rely on your manufacturer any more in case of malfunctioning. Yes, the efficiency of panels keeps going down little by little, but they are still producing energy. You don't have to immediately remove them from the roof: keep them checked, keep them clean and they will keep doing their job for many more years.

So is the investment worth it? Or to be more precise, would solar panels bring in more money in 25 years than their initial cost plus installation cost plus all the parts of the system plus this degradation rate? The answer is "yes" in almost any case. The average solar payback time in the USA is around 8.5 years. After that, all that solar panels bring in is a pure profit. Most of the time it's not even a question about how much energy your solar panels produce, but rather how much electricity costs in the state. In our recent article we demonstrate how an investment in solar panels can be justified even in (and sometimes especially in) cloudy states where on paper you end up with less free electricity — come check it out!
8.5 years is the average solar payback time in the USA
Illustrations – Marina Fionova
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