Coupled resonators appear as the building blocks of many systems and devices. Recently, Energy Coupled Mode Theory (ECMT), a general coupled mode formalism in an eigen-value problem form, was introduced to estimate the frequencies and fields of an arbitrary number of coupled resonators. In the current article, impressed sources are introduced to generalize ECMT to cover cases where arbitrary input excitations are applied. The system is represented by a matrix transfer function in the complex domain. To demonstrate how the transfer function can be applied, the efficiency of a classical system of two inductively coupled resonators is calculated under different load values and input frequencies.