What Is a Panel Degradation Rate?
Panel degradation rate is the gradual, expected loss of a solar panel’s power output as it ages, stated as a yearly percentage decline. Every panel degrades, the loss is slow, and both production estimates and manufacturer performance warranties are built around an assumed decline.
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Panel degradation rate is the gradual, expected loss of a solar panel’s power output as it ages, stated as a yearly percentage decline. Every panel degrades, the loss is slow, and both production estimates and manufacturer performance warranties are built around an assumed decline.
Panel Degradation Rate explained
Silicon cells slowly lose some of their ability to convert light. Most of the loss happens in two phases: a small drop early on as the cell settles, then a steady, gentle decline for the rest of the panel’s life. Heat, humidity, and long exposure to strong sun speed it up, and cell design matters, since some technologies age more slowly than others. Manufacturers publish an expected decline and back it with a performance warranty.
Homeowners ask about it in plain language: do panels stop working after a few decades? They do not. They keep producing, just a little less each year. Savings projections and production estimates should state their assumed degradation, because a long-run projection that ignores it overstates future production. In a PPA, where the homeowner pays for each kilowatt-hour produced, slow output decline and any yearly price escalator both shape the long-run bill.
Degradation is not the same as damage. A hail strike, a cracked cell, a failed bypass diode, or a manufacturing defect shows up as a sudden or uneven drop, and that is a warranty or insurance question, not normal aging. The other trap is assuming the published rate is what every roof experiences; climate and installation quality change it. And a low rate does not rescue a poorly designed system, because shade and direction matter far more in the early years.
Why it matters when you're buying
Longevity questions usually come from the careful reader in the household, the one who reads the fine print. The plain answer is that panels keep working but produce a little less each year, and that the proposal accounts for it. Skip the topic on the first call and it returns during proposal review, when the answer has to be exact.
Frequently Asked Questions
How much do solar panels degrade each year?
What happens to solar panels when the performance warranty ends?
Is degradation the same as a panel defect?
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