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November 7, 2017


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When purchasing a machine it is common for us to estimate its value at least partially on its lifetime. We use the word “life” to refer to the time period or beyond which the machine no longer offers significant value to the owner. Automobiles, for example, regularly last for at least 10 years or up to 150000 miles. Many stick around longer.

The biggest ticket item in the solar system are the panels. They can represent one third of the cost of the system, so how long are they good for? Solar panel performance today is guaranteed by the manufacturer for 25 years. Many cite this as the lifetime of the panels but really this just represents when the panels are guaranteed to be operating at 80% of their factory rating. Beyond this, the panels may continue producing a significant output for 10 years so that in total a solar system can output useful power for a solid 35 years.

Panel lifetime also varies by climate. In an interesting study, a 20 year old solar system degraded in power output by only 3%.