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Remember when you bought your first car, and the salesperson kept emphasizing how great that particular model was because it would ‘outlast’ the competition? By a show of hands, how many of you are still driving that first car? Not many right?

Moving parts means wear and tear, and there comes a point where it’s almost not worth it to sink more money in an old junker. But what about a technology like solar panels that have no moving parts? You’ve probably heard every answer in the book, but how long do solar panels really last?

Believe it or not, there are still solar panels and cells out there that are cranking out electricity after more than 50 years!  Just look at some of the satellites whizzing around Earth that maintain their orbits with solar technology. There’s even a British solar contraption that can still produce solar energy after 65 years!

But you’re naturally concerned with the solar panels for your home, not ancient science experiments or spacecraft. Most solar panel manufacturers have a standard guarantee that specifies their products will last at least 25 years, but those are extremely conservative estimates.

In 2012, NREL, the National Renewable Energy Laboratory, tackled the question of solar longevity and found that traditional silicon-based solar panels (i.e. the ones for your home), only lose about 0.5% of their efficiency per year.

That means that (in a perfect world) your residential solar panels would still be roughly 88% efficient at the end of that manufacturer’s warranty. Typically the big manufacturers will guarantee at least 80% efficiency at the end of the 25-year expected lifespan, but there are a few positive exceptions.

There are several things that cause long-term degradation in the panels, but the simple answer is they’re just working hard, day after day, and it takes its toll. After being exposed to sunlight and the elements for decades on end, the encapsulating material eventually starts to crack slightly and contaminants (like water vapor) are able to infiltrate the cell.

The thermal stresses can also deteriorate the anti-reflective coating which ultimately leads to a decrease in efficiency.

But a decrease in efficiency does not mean the panel isn’t working. Indeed, there are solar power systems in California that are going on thirty years and still producing clean, solar energy for their owners.

Unlike a new car, which is going to immediately depreciate once you drive it off the lot, new solar panels are going to be saving you money so long as the Sun is shining, not costing you money over their lifetime. On average, a typical 6-kilowatt solar power system will pay for itself in five to nine years, and anything after that is just money in the bank.

You can learn more about the long-term benefits of buying solar panels for your home by downloading your free copy of our Ultimate Guide to Going Solar .

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