We present an efficient way to compute the acoustic energy within complex-shaped geometries and obstacles inside cavities in the mid-high frequency range. The method is based on energy flow, known as the Simplified Energy Method (MES), considered quite accurate in this frequency range. However, its performance is primarily effective in simple cavity shapes and does not adequately address obstacles within the domain. We then propose a hybrid method that couples ray and triangle intersection techniques with the MES formulation. This method involves calculating ray intersection points to identify blocking elements before computing the energy transfer in each boundary element. We rely on a primary intersection state matrix, which contains the overall information of the direct view between elements. This matrix is then integrated into a modified MES equation, thereby disabling unnecessary computation and ensuring precise energy transfer of blind couples. The hybrid formulation is applied to both direct and reverberant fields to calculate the total energy density. Numerical simulations are conducted in a complex domain enclosure and compared with traditional MES calculations and physical properties. The simulation results demonstrated the accuracy of the proposed algorithms, and the computational cost is analysed and appears to be totally suitable for shape optimization problems, as it usually involves many ‘call’ of the objective function.