Performance Degradation Warranty

A performance degradation warranty (also called a power output warranty or linear performance warranty) is a guarantee from the solar panel manufacturer that the panel will maintain a minimum percentage of its original rated output over a specified period — typically 25–30 years.

A standard performance warranty guarantees that a panel will produce at least 84–87% of its nameplate output after 25 years. Many premium manufacturers now offer 30-year warranties guaranteeing 88–92% of original output. “Linear” warranties guarantee a smooth, predictable decline each year (e.g., no more than 0.4% degradation per year), while older “stepped” warranties might allow up to 10% degradation in the first 10 years and 20% by year 25. If a panel’s tested output falls below the warranty threshold, the manufacturer must repair, replace, or compensate for the underperforming panel. However, filing a warranty claim can be complex — you need independent testing to prove the panel is underperforming, and the manufacturer may no longer be in business decades later. This is why choosing panels from established, financially stable manufacturers is important for long-term warranty security.