According to the manufaturers, solar panels typically have a lifespan  of 20-30 years,  and it is common for their power to decrease after 10 years. For instance, a panel that originally produced   300 W of power may decrease  to  240 W after  20 years.

The guarantee itself is given for the correctness of the system, and it is usually two years. So any mechanical damage is not covered by the warranty.

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