This paper presents a hybrid formulation in frequency domain, which combines the method of moment (MoM) with the edge-based vector finite element method (FEM) to solve electromagnetic field distribution inside a loaded enclosure with aperture. While the FEM is used to solve EM fields inside the enclosure, the MoM is used to solve the surface integrals related to the aperture field components using equivalent surface currents. Numerical results of shielding effectiveness (SE) and stored electrical energy (SEE), calculated by the hybrid method for an enclosure with aperture, are presented and validated by comparing with previous results in literature. Then, the hybrid method was applied to loaded enclosure and the SE, SEE and dissipated power (DP) in load were determined. In this work, SEE and DP were examined at two frequencies by changing the location of the dielectric slab inside the enclosure with aperture. © 2011 ACECR.