How Long Do Solar Panels Last?

How long do solar panels last? Look at this old solar system!

After 40 years on a roof they’re still producing at 80% of their capacity.

According to Andy Black at the PG&E solar class at the Pacific Energy Center, some of the very first solar panels made back in the ’70s are still pumping out power up in Northern California after 40 years, and they’re still at about 80% of their original power ratings.

According to Black, all solar panels lose about half a percent a year in efficiency. They are warrantied to 25 years because at a half percent a year, in 25 years they’ve lost 12.5% of their original power. The panel still retains 87.5% power output, it’s just that the panel manufacturer can’t claim a panel is producing X power when it’s producing 12.5% less power than when it was originally tested. After 25  years, a 10 KW system is now a 8.75 KW system, and a 4 KW system is now effectively an 3.5 KW system.

Although the solar array on your home will likely not be worth as much as new panels in 25 years, it should have paid itself off many times over and will still be producing free power for your home.* There is no reason to buy new panels if the ones you already have are still producing enough power for your needs.

* This is based on information from