This paper deals with the electromagnetic mod-eling of large and complex electrical structures by means of extensive parallel modeling based on grid computing (GC). The numerical modeling is based on a hybrid approach which combines Transmission Line Matrix (TLM) and the mode matching methods. The former is applied to homogeneous volumes while the latter is used to describe planar structures presented within the entire simulation domain. The results prove the benefits of the combined GC and hybrid approach to solve electrically large structures. Index Terms— Transmission line matrix methods, mode matching methods, grid computing, high performance computing , large-scale systems.