This paper provides a metric definition for the safety failures, reliability failures and degradation loss for the PV modules. These metrics are then used in real power plant evaluations to calculate the distribution among these three metrics which in turn could objectively be used to perform financial risk calculations. The results obtained on 2352 and 1280 modules in two of the evaluated power plants, aged 12 and 4 years, in a hot-dry desert climate are analyzed using these defined metrics. The results indicate that the mean and median degradations, respectively, are 0.95 and 0.96 %/year for the 12-year old, and 0.96%/year and 1%/year for the 4-year old power plants. The distribution between safety failures, reliability failures and durability loss is determined to be 7%, 42% and 51%, respectively for the 12 year old power plant.