Understanding the energy loss in piezoelectric materials is of significant importance for manufacturers of acoustic transducers. The contributions to the power dissipation due to nonzero phase angles of the mechanical, electrical, and piezoelectric constants can be separated in the expression for power dissipation density. However, this division into separate contributions depends on the piezoelectric constitutive equation form used. Thus, it is problematic to identify any of the three terms with a specific physical domain, electric or mechanical, or to a coupling as is common in the discussion of loss in piezoelectric materials. Therefore, assumptions on the phase of the material constants based on this distinction could be erroneous and lead to incorrect piezoelectric models. This study demonstrates the challenge of distinguishing mechanical, electrical, and piezoelectric losses by investigating the power dissipation density and its contributions in a piezoelectric rod for all four piezoelectric constitutive equation forms.