How Long Do Solar Panels Last?

By Roy L Hales

Screen-shot-2014-03-18-at-3.43.47-PMThough many believe the lifetime of a solar panel is twenty-five years, a number of older models have exceeded this. When Kyocera tested a 30-year-old module, last year, they discovered it was still operating at 90.4% of capacity. There are 37-year-old Arco Solar (now SolarWorld USA) panels in operation. So How long do solar panels Last?

Peter Varadi [1. co-founder of Solarex, the World’s first solar company (1973-83) and author of Sun Above The Horizon: Meteoric Rise of the Solar Industry] suggested that Dr. John Wohlgemuth may be the person to answer the question – how long do solar panels last?

Dr. Wohlgemuth started working at Solarex, the world’s first terrestrial solar company,  in 1976. He continued on with BP Solar, after it bought out Solarex, and eventually became the Principle Scientist in PV Reliability the National Renewable Energy Laboratory.

In response to my email, he wrote:

“As far as I can tell there is little difference between the early Solarex, Arco and Kyocera modules in terms of their ability to survive. I have seen modules from all 3 survive at least 30 years in the field.

“There were several excellent papers at the last EUPVSEC conference that reported on the performance of Solarex modules after > 25 years of exposure and I have some with at least that long exposure that are still working.

“I do not think those old modules will survive 50 years. First of all because of the EVA formulation they used, they are all discoloring – which means loss in short circuit current (~ 0.5% per year) and loss of adhesion – recent results show Arco modules at 10% of initial adhesion between EVA and glass after 27 years in the field.

“The older modules are losing output power. As I said earlier about 0.5% per year due to discoloration. They also slowly lose fill factor as they used interconnect ribbons that are much stiffer than the ones used today. Once they get to 25 to 30 years they are typically approaching 80% of initial power.

“I am not sure what I expect from the more modern modules. They use better raw materials – encapsulants that don’t discolor and much more flexible interconnect ribbons that do not stress the solder bonds or cells as much. So then you have to look at manufacturing control. I would have to think that some of the newer manufacturers have at least as good a control as we had 25 years ago. Many of the new modules are tested significantly more rigorously than the old ones were.  On the other hand if manufacturers take too many short cuts to cut cost then the quality will suffer. So some of the new modules will be at least as good as the ones from the 1980s and 1990s, but others will not be.  We have to figure out how to determine which is which and not use the ones that will not survive.”

So it looks like some of the old solar panels could last more than forty years, possibly a little longer, though at a reduced capacity. Some of the better made new modules may have even more longevity.

Students inspect the Dana Building’s solar panels in 2010 from University of Michigan School of Natural Resources & Environment (CC BY SA,2.0 License)