3 Best Solar Panels of 2026, Lab-Tested and Reviewed

What Makes a Good Solar Panel

The lifespan of a well-made solar panel, also known as a photovoltaic module, is about 30 years and potentially longer, according to the Department of Energy. You want your solar array to be making energy as efficiently as possible for that entire time. Some panels perform better than others because of how they are made, says Erion-Lorico.

“You can use a lot of materials and manufacturing processes to make a solar cell and a solar panel, and not all of those materials perform the same,” he says. “You can use different encapsulants, which are the glue that holds the panel together. Some of those encapsulants have higher transparency than others, allowing more light to reach the cell. Cell designs can be quite different.”

One way to discern a solar panel’s long-term effectiveness is with its “degradation rate,” which can often be found in the manufacturer’s power warranty information (or ask your installer). All solar panels are expected to dip in effectiveness over time. But the lower the degradation rate, the better, because your solar array will be working as close to maximum capacity as possible throughout its lifespan.

For instance, the Jinko Solar panel we tested has a first-year degradation rate of 1 percent, according to the manufacturer. Each subsequent year, the degradation rate drops to 0.4 percent or less. That means that after 30 years, the panel should be creating energy at a level that’s 87.4 percent of its first-year output, or greater. That’s at least 367 watts per panel after 30 years, assuming the panel starts out producing 420 watts.

Of course, extreme weather can affect any panel’s degradation rate. Kiwa PVEL also produces a scorecard with data on long-term reliability.