The main purpose of the present study is to compute the input energy spectra of selected far-fault ground motions (GMs) for linear elastic systems, and inelastic systems having a constant ductility ratio. Elastic-perfectly plastic (EPP) and Modified Takeda hysteresis models have been adopted in nonlinear modeling of single-degree-of-freedom (SDOF) systems. Accelerograms of far-fault GMs have been compiled from the Pacific Earthquake Research Center (PEER) database. Linear and nonlinear time history analyses have been performed using the selected GMs records for SDOF systems having a damping ratio of 5%. Input energy spectral ordinates have been computed in terms of energy equivalent velocity. The results have shown that there is no significant difference be tween elastic and inelastic input energy spectral values at intermediate and long periods. However, for short period systems, input energy demand imposed on inelastic systems is generally greater than that of imposed on elastic systems. For short period systems, it can be inferred from the computations of the study that the input energy spectral values obtained using Modified Takeda hysteresis model are greater than those of other models that have been employed. However, input energy spectra for inelastic systems have no significant dependency on hysteresis models, especially for intermediate and long period systems.