Sound radiation from vibrating structures is a crucial concern in the vehicle design process. One effective tool to recover vibration patterns on surfaces is the surface contribution analysis. Recent implementations, however, focus on surface contributions with respect to single evaluation points. For a contribution analysis regarding an entire volume, the tedious volume integration is required. This study aims to develop an efficient contribution analysis technique for the acoustic evaluation of an entire cavity. In order to circumvent the cumbersome volume integral, the acoustic quantities are evaluated at regularly distributed field points. For this purpose, the three-dimensional Helmholtz equation is solved by using the boundary element method. Moreover, the eigendecomposition of the accompanying coupling matrices is involved in the proposed method. In contrast to traditional techniques, the sound energy is deployed as the objective function, since the sound energy is not only sensitive to the sound pressure but also to the particle velocity. Another beneficial aspect is that the energy-based contributions are nonnegative. In this way, acoustic short circuits are avoided. The proposed method is validated for two numerical examples: the inward radiating sphere and the vehicle interior noise problem. Initial findings already reveal that entire volumes can be analyzed with the energy-based contribution analysis. By this means, our method designates an efficient method to evaluate contributing surfaces with regard to entire cavities. This research emphasizes the relevance of an energy-based contribution analysis, since they provide deep insights into the acoustic behavior of cavities.