This paper presents an investigation of power and energy transduction in piezoelectric wafer active sensors (PWAS) on isotropic structure for structural health monitoring (SHM). After a literature review of the state of the art, we developed a power and energy model for PWAS on an isotropic beam. We performed 1 -D and 2-D model of the power and energy transduction for PWAS transducers attached to structure. This 1-D and 2-D model allows examination of power and energy flow for linear and circular crested wave pattern. The power and energy transduction flow chart for a complete pitch-catch setup is examined. At each stage, the electro-acoustic power and energy transduction of the PWAS transmitter and receiver are examined. The power flow converts from electrical source into piezoelectric power at the transmitter, the piezoelectric transduction converts the electrical power into the mechanical interface power at the transmitter PWAS and then into acoustic wave power travelling in the structure. The wave power arrives at the receiver PWAS and is captured at the mechanical interface between the receiver PWAS at the structure. The mechanical power captured is converted back into electrical power in the receiver PWAS and captured at the receivers electric instrument. The parametric study of PWAS size, impedance match gives the PWAS design guideline for PWAS sensing and power harvesting applications.