Let’s Talk About Reliability and Longevity of Solar

How much electricity will the solar panels I bought today produce when they are 25 years old?  How fast do they degrade?  A recently released movie, produced by Michael Moore of all people, says solar panels are only good for 10 years.  Unfortunately for Michael Moore, that is one of the most ill-informed statements on the subject that I have ever heard.  Here is the reality:

That’s fine, you say, but do those reports reflect what happens on my roof?  The rooftop solar project on our house has been up since September 2005, so let’s take a look at that.  With 83% solar access, the predicted output on year one was 5,985 kWh.  We also expected the production to drop by 0.4% per year, as shown on the chart below.

 house pv production 6 2020

What we are seeing here is variability due to weather, but no downward trend.  If you throw out the first year, during which the amorphous silicon layer on the cells of the Sanyo solar panels overproduced until annealed, the average yearly output is 5,879 kWh, just a few kWh less than what was predicted.  In the winter of 2010 one of the inverters failed and that is the only issue that we have had with this project in 15 years.   We did determine from weather data that the Seattle area has been getting a little more sun each year, delivering a bonus of about 2,140 kWh.

Other projects that we installed back then are showing similar results.  In 2006 we installed 21 kW for the Department of Ecology at their facility on Padilla Bay.  First full year of production in 2007: 24,714 kWh.  2019 production: 25,314 kWh.  I think we can count on the sun and photovoltaics to deliver all the energy we need for the long haul.

About the author


Started Puget Sound Solar in 2001 with 30 years of construction contracting experience, and a desire to turn Seattle on to solar energy. Achieving NABCEP certification in 2004, Jeremy believes that our customers often follow a path similar to the one he took, starting out with solar daydreaming, then progressing to education on the subject, and eventually leading to action. In addition to leading the company he also does some teaching and speaking engagements about various aspects of solar energy, and experiments relentlessly with various solar, energy efficiency, and electric vehicle projects.

Jeremy Smithson

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