Exactly how much do solar panels wear out over time?
Last updated on 10/28/19, by Esmeralda Torres | Written by Nina Goodey
While solar panels degrade a little every year from exposure, they’ll last you decades and they’re an excellent investment, new or used.
Efficiency vs. Lifespan
If you’re shopping around for the best solar panels to buy, then you know that efficiency and lifespan are factors you should keep in mind.
First off, it’s important to know the distinction between efficiency and performance. Efficiency refers to how well the panel converts sunlight into energy - most of it is lost. Even with all the technological advances made in the last few decades, most panels range in efficiency from about 15-24%, depending on the manufacturer and kind of panel. Performance, on the other hand, refers to how much of the panel’s maximum power output you’re getting. New panels start out at almost 100% and after 20 years drop to around 80-90% performance, depending on the manufacturer and panel.
To sum it up: efficiency is about how good the solar cells are at converting light to electricity and that’s a low percentage, and performance is about how well a panel continues to generate power as it ages, and that’s a high percentage.
Keep in mind, efficiency ratings may sound impressive, but record-setting panels typically achieve those rates in specific laboratory situations. If you need a 250W panel, any well-made 250W panel will get you that power. Typically, efficiency matters when you want fewer, more powerful panels to fit on your limited roof space.
Ok, now that you understand the difference between efficiency and performance and what those terms mean, let’s talk about degradation. Panels are built to withstand high and low temperatures, snow, hail, and other hazards, but they’ll still break down a little over time. Gradual decreases in your panel’s performance can be caused by UV exposure, bad weather, scratches, or other causes. A pretty standard rule of thumb is to expect a 3% decrease in the panel’s first year, and then about a 0.5% drop every year after that. This can vary depending on location - panels in a moderate climate might only have a 0.2% drop every year. Other conditions might worsen up that decrease - such as cracks in the glass or moisture in the cells.
So now you might want to know what kind of output you can expect from your panels 25 years from now. We don’t quite know either - technology has improved rapidly enough that it’s tricky to predict how well panels made now will function in 20 or 30 years. Solar panels can be surprisingly durable - the world’s first modern solar panel still works, a panel made in 1979 actually outperformed its original factory specifications, and many other older panels still function well even after their warranty expired.
Alright, so panels are a good long-term investment. Which panels are the best though? Well, that’s up to you to decide depending on which factors are most important to you - whether you want top of the line panels or less expensive but still dependable panels.
At Santan Solar, we have a number of used, overstocked, and refurbished solar panels. Given how well panels continue to perform after a few years, you could save a lot of money and still find the high-quality, high-efficiency panels you need. All our panels are checked and tested to make sure they’ll still work well for you, and come at a much lower price than new panels. Learn more about the benefits of used panels here, see which panels we have in stock here, or contact us here if you have more questions