The effectiveness of the energy-dependent finite element method (EDFEM) as applied to two-dimensional multigroup diffusion problems is investigated. The EDFEM couples the finite element method (FEM) formalism with the energy-dependent element size scheme. The EDFEM allows the elements to straddle material interfaces if certain conditions are satisfied; this method is especially suitable for heterogeneous reactor calculations. Comparisons of the results obtained by the EDFEM, the FEM, and the finite difference method for a ZION I pressurized water reactor model are presented. A significant reduction of the total number of unknowns involved in the problem is accomplished by using the EDFEM, which yields a reduction of the computing time by 30%.