What can I learn from the PV system survey? The survey assesses the so-called performance ratio of real-world PV systems. It's a measure of overall system quality. Every system owner should know about it since the performance ratio gives you a much needed reality check. The performance ratio, abbreviated as PR, specifies the difference between what you paid for and what you actually get. PV systems are sold in terms of kilowatt peak system size, but their output is always reduced by an additional factor - and this factor is just the performance ratio. Often generic values are used for the performance ratio neglecting the fact that performance varies widely from system to system. An actual system can have a PR as low as 50% or as high as 90%. By taking a look at our PV system survey, you get a better idea how your own solar system compares with others in the directory.