Over time, a PV module will degrade. After all, if you leave anything in the scorching sun for 25 or more years, it will eventually degrade, including roofs and paint jobs. Certain PV modules are less subject to degrading over time than others, however, and SunPower’s E20/327 Solar Panels recently earned its weight in gold by achieving the lowest Potential Induced Degradation (PID) in testing by PV Evolution Labs.

PID is a leakage problem where current from the solar cell is drawn to the panel frame, thereby degrading a PV panel’s power output. Unfortunately, this process is accelerated by temperature, humidity and voltage—all of which a PV module must be built to resist for a lifetime. PV Evolution’s testing is designed to stress modules to see how they respond to stress over time. Determining failure rates and production losses can help investors determine the risk of a manufacturers’ product failing.

During the rigorous testing, which includes 600 hours (the equivalent of 25 days of stress) of damp heat conditioning and maximum rated voltage stress, SunPower’s modules only showed 0.2 percent degradation. The modules are evaluated using visual inspections, flash testing and high-resolution electroluminescence.

“The average degradation of modules that passed this test is approximately four to five percent,” a spokesperson for SunPower said.

A full 50 percent of the modules that PV Evolution tested failed to pass its testing.  In order to pass, modules must have less than five percent power loss after 100 hours of testing and less than 10 percent after 600 hours.  Those that failed the test exhibited power loss from 18 to 87 percent during testing.

SunPower earned PV Evolution certificates in all grounding configurations. “This third-party testing program confirms that SunPower solar panels are virtually PID free in any grounding configuration and offer extreme resistance to degradation, with the results surpassing the nearest conventional panel,” stated Tom Werner, SunPower President and CEO. “As a solar technology leader, we are committed to providing our customers with third-party validation, assuring them that they are buying the most reliable panels on the market today.”

This is the latest third-party validation for SunPower’s modules. The company said the same module also recently received an unprecedented reliability rating from Atlas Material Testing Technology, which showed less than a two percent power drop across all degradation tests performed. The Fraunhofer Institute said SunPower’s module ranked first in its PV Durability Initiative testing. And, in last year’s Photon 2012 Module Yield Test SunPower’s E-Series Solar Panels placed first, second and third out of 151 participating solar manufacturers.