This paper describes the comparison method of input powers and contribution rates from vibration sources to a small power generator's enclosure represented by a thin-walled plane structure determined by Statistical Energy Analysis (SEA) and Transfer Path Analysis (TPA). In the pursuit of efficient ways to analyze the design dynamics of small machines such as a small power generator, it is important to identify information and dynamics of input power sources during machine operation. SEA and TPA are two of the most efficient methods in identifying the dynamics of a structure during machine operation. SEA is used for systems with many resonant modes, and predicted results are based on space averages. On the other hand, TPA is based on estimation of a frequency response function between an excitation point and a response point. In this study, we proposed a method to compare SEA evaluated by power injection method and TPA evaluated by matrix inversion method. The method is validated through numerical analyses, using a finite element method (FEM). We focused our research on the enclosure of a power generator and simplified it by constructing a partial enclosure model of a simple structure consisting of two L-shaped plate structure. In order to verify the practicality of this method, an experimental verification was conducted. As a result, the input powers are quantitatively similar between SEA and TPA. Furthermore, the contribution rates from the power sources between SEA and TPA are qualitatively similar without having to consider the response phase.