Piezoelectric generators enable maintenance-free power supply for integrated electronics in smart system applications. The majority of publications consider the aspect of power transfer electronics; however, the influence of the transducer materials was rarely described. Recently, material characteristics received increased attention from the ceramics community. We set the focus of the present paper to commercially available piezoelectric ceramics. Different figures of merit are derived from system analysis using electromechanical modeling. They allow for the description of typical load scenarios and commercial piezoceramics. Derived rules are expected to be helpful for guiding ceramic engineers and system designers to succeed in improved generator solutions.