Aging Solar— Should I Be Concerned?

By Gene Beck

Solar photovoltaic (PV) systems have experienced phenomenal growth in recent years, evolving from a niche market to a mainstream electricity source for residential buildings. Today, the electric energy future belongs to those homeowners who innovate, and many Southern California homeowners have done exactly that by installing photovoltaic systems on their homes over the past twenty years.

Now, some early adopters of solar energy are asking, “Is it time to replace or upgrade my system?” If you are keeping your home, it is natural to consider the value of new PV because prices have dropped more than 80 percent in the past ten years. Other people are considering purchasing an existing home with solar and are concerned about both PV system failures and the effect an older system might have on roof integrity.

So, should you worry about that solar photovoltaic system on the roof?
Simple answer: If it isn’t broke, don’t fix it!

Those existing panels are doing quite well in producing electricity for you day after day with as little maintenance as washing the panels off with a hose once or twice a year and making sure there is no shading throughout the day and the season. And they have been protecting your existing roof extremely well over the years. Unless you need to replace your roof or want to change its appearance, leave things alone.

Quality and reliability continue to be critical elements for steady growth in the solar industry. The equipment is expected to perform reliably on a roof for more than twenty-five years, with a maximum degradation of only 10 percent in ten years and 20 percent in twenty-five years (even in extreme environmental conditions). California will not allow solar photovoltaic panels to be sold in the state without this minimum guarantee from the manufacturer.

New panels on the market have a small improvement in output per square foot but not enough to consider upgrading for economic reasons. Yes, the cost of purchasing solar panels has dropped by as much as 80 percent in ten years and is still declining; however, the panels and related equipment represent only 35 percent of the total cost of the photovoltaic system. Installation, permits, and the support equipment needed account for 60 to 70 percent of the cost (see Table 1), and these costs have gone up, not down.

In 2010, the installed cost of solar panels was $7.24 per watt, and in 2017 costs went down to $2.80 per watt. This downward trend will continue, albeit at a slower pace. The National Renewable Energy Laboratory (NREL) also reports that failure rates are relatively low at 5 in 10,000 installations annually. You can be sure that the roof will wear out long before the photovoltaic system will fail or no longer be productive.

Not long ago, the California Building Standards Commission (CBSC) unanimously confirmed new standards requiring that solar photovoltaic panels to be installed on new low-rise residential buildings starting January 1, 2020. Builders who do not incorporate solar PV in new construction will not be able to pull permits to build.

My bet is that a solar panel installed today will be up and running (and still generating at 70 percent of initial output) thirty to forty years from now. The truth is that electrical rates from utilities in Southern California are increasing faster than solar panels are degrading!

Causes of Solar Panel Degradation

  • Extremely cold climates—heavy wind and snow loads
  • Extremely hot climates—with long periods of ultraviolet exposure
  • Anything “caked” on the panel—including dust, dirt, leaves, cement dust, and paint overspray

Photovoltaic System Owners Should

  • Obtain copies of the original contract and all permits
  • Obtain copies of the warranties on all system components
  • Evaluate the shading from nearby structures or landscaping
  • Check out the manufacturer(s)
  • Inspect applicable homeowners’ association documents
  • Inquire about the financial stability of homeowners’ associations in surrounding areas. Their lack of tree trimming may affect the output of your panels!

Gene Beck is the Executive Director of the Green NRG Institute and author of Grid Parity: The Art of Financing Renewable Energy Projects and the Dictionary of 21st Century Energy Technologies. His email address is