Solar Panel Warranty Explained

For those new to solar, understanding solar panel warranties can be quite confusing due to the two very distinct warranty conditions, a product warranty and a performance warranty. Like most products and appliances, solar panels have a manufacturer’s product warranty that protects against any failures due to faulty materials or workmanship. Solar panels also have a secondary warranty condition, known as the performance warranty which accounts for a slight loss in performance or degradation over the life of the panel.

1. Product Warranty

The product warranty is the manufacturer’s warranty that protects the customer against defects that may have occurred due to manufacturing errors, quality issues, or component and material failures. This means the manufacturer must either replace or provide a refund for solar panels which fail within the product warranty period. In general, solar panel manufacturers must provide a minimum 10-year product warranty period, however, a growing number of premium manufacturers now offer 15, 20 and even 25-year product warranties.

2. Performance Warranty

The performance warranty also referred to as the power output warranty ensures that the solar panel still produces a minimum amount of power output after the expected 25-year life of a panel. Once installed outside and exposed to sunlight, UV radiation, and high temperatures, all solar panels slowly reduce power output over time due to a well-known phenomenon called Light Induced Degradation or LID. Typically 3% is lost in the first year, while the annual loss over the remaining 24 years is much less, at around 0.3% to 0.7% per year.

The industry standard is 80-84% retained power output after 25 years. However, some high-end manufacturers, such as Sunpower, LG, and REC guarantee as much as 88% to 92% remaining power output on most modules after 25 years of use. There are also a growing number of manufacturers offering 30-year performance warranties on the unique dual glass and bifacial solar modules.

Performance Warranty Explained

Rooftop mounted solar panels are generally very reliable, have no moving parts and require very little maintenance. However, it is normal for solar PV cells to experience a small amount of degradation over time. Solar panels are expected to perform under a wide variety of very extreme environments, from freezing winter conditions to very high summer temperatures, high humidity, wind, and severe UV radiation, not to mention salt mist corrosion in coastal seaside locations. Due to these extreme conditions, all solar panels experience some minor degradation due to several known phenomena

Solar panel degradation rates vary significantly depending on the type of cell-substrate used by the manufacturer of which there are two main types, P-type and N-type. Panels with the least amount of degradation are those built with a high-grade  N-type silicon substrate. These high-performance N-type cells have a lower rate of light induced degradation and can expect to lose only 0.5% per year, which equates to close to 90% retained power output after 25 years of use. Due to the lower cost of production, most manufacturers use P-type cells which have a slightly higher rate of degradation at approximately 0.8% per year.

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