Longevity of Solar Panels: | Simply Solar
Purchase, Maintenance, and Replacement Strategies

One of the key questions consumers ask when going solar is “How long will my system last?” This can be a critical factor when deciding not only what to install on your home, but which manufacturers to trust and which companies to contact. Most of all, it is important to know that an investment in solar will be one that pays off quickly. Today, we are looking at the longevity of solar panels. In addition to learning about their typical lifespan, you will also see how to improve your system and keep it generating power for your home for many years to come.

How Long They Last

Most solar panel manufacturers offer an industry standard warranty of 25 years. This is based on research evidence that shows panels lose efficiency at a rate of 0.5 – 1 percent each year. What this means is that a solar panel will decline in efficiency each year until it reaches a point at which its lack of efficiency makes it necessary to replace the unit.
To be clear: The 25-year window does not mean that solar panels will eventually fail completely after a certain period of time. Instead, this information gives you an idea of how long your solar panels will be able to harness solar energy. At the end of five years, you can expect your solar panel to operate at 95% efficiency (or better). 
The national average decline is roughly .8% (as of 2012), although different panels offer different rates. Silfab panels come with a 25-year warranty, reflecting the national rate of decline. In fact, after 25 years Silfab panels are expected to produce at 80% or higher.

How to Improve Longevity

One of the best qualities of solar panels is that there is little maintenance involved. There are no moving parts, and the solar panels work with the connected inverters to harness and convert the sun’s energy into electricity that will power your home or business. Because of this, it can be easy to forget that the solar panels are there at all.
Although degradation is inevitable, there are steps that consumers can take to prolong the life of their systems. The first step is to simply monitor the energy output of the system. If you notice that production is beginning to slip, but you have not reached the end of your warranty, you might need to clean the panels or check for obstructions (shade from trees and chimneys are common obstacles).
Aside from checking the system, you can improve the longevity of the panels by cleaning them on a regular basis. This does not mean that they require a deep cleaning every week (or month). Most panels will benefit from a cleaning once per year. The exception to this is cold-weather areas; you may need to brush the snow off the solar panels after a heavy snowstorm. The other exception is dusty, dry areas (such as the southwestern US) or homes near freeways and airports. The panels on these homes generally accumulate more dirt and pollutants over time, which means you may need to clean them more often. Again, if you see that production is beginning to wane, it is a good time to speak with your solar company.

Sources
https://www.ecodirect.com/Silfab-Solar-SLA-300M-300-Watt-Mono-Solar-Panel-p/silfab-sla-300m.htm
https://www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/7475/What-Is-the-Lifespan-of-a-Solar-Panel.aspx
https://news.energysage.com/how-long-do-solar-panels-last/