In this paper, a simple model of the energy consumption of RLC tree circuits under exponential inputs is presented. The modeling approach is based on the reduction of a RLC tree network to a proper 2 nd -order RLC equivalent circuit. The extraction of the 2 nd -order RLC equivalent circuit is very simple, thus leading to an efficient model that is suitable for fast simulations.Closed-form expressions of the energy consumption are derived. The resulting expressions allow for understanding the effect of the inductance and the shape of the input waveform on the energy consumption. Extensive SPICE simulations show a typical error lower than 1%, confirming that the model exhibits very good accuracy despite of the simplicity of the adopted approach.