The bonding is highly durable. The practical experience on butyl glues, used on the bottom of the panel, dates back over 30 years. The protection film is manufactured by 3M and chosen amongst over 100 different products after comprehensive tests. The operating life of the protection film has been several dozens of years, in salt fog test and demanding sunny conditions, among other circumstances, in the climate chamber tests conducted in a laboratory environment. After 25 years, the output of the panels is at least 80% of the original level. The actual product guarantee against breakdown is 5 years.