In this paper new formulations for the energy dissipation of lossy transmission lines driven by CMOS inverters are provided. These formations are obtained using an approximated expression for the driving-point impedance of loss coupled transmission lines which itself is derived by solving Telegraphers equations. A comprehensive analysis of energy if performed for both step and flattened ramp inverter inputs. To accomplish this task a new stable circuit that is capable of modeling the transmission line for a broad range of frequencies is synthesized. Experimental results show that the energy calculated using this equivalent circuit is almost equal to the one calculated by solving the more complicated transmission line equations directly.