Solar Panel Life?

Photovoltaic (PV) modules typically come with 20 year warranties that guarantee that the panels will produce at least 80% of the rated power after 20 years of use. The general rule of thumb is that panels will degrade by about 1% each year. Is that rule accurate?

The National Renewable Energy Laboratory (NREL) performed a meta-analysis of studies that examined the long term degradation rates of various PV panels. They found that the 1% per year rule was somewhat pessimistic for panels made prior to the year 2000, and today’s panels, with better technology and improved manufacturing techniques, have even more stamina than their predecessors. For monocrystalline silicon, the most commonly used panel for commercial and residential PV, the degradation rate is less than 0.5% for panels made before 2000, and less than 0.4% for panels made after 2000. That means that a panel manufactured today should produce 92% of its original power after 20 years, quite a bit higher than the 80% estimated by the 1% rule.

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