The Z-pinch fusion energy power plant concept is based upon an X-ray driven inertial confinement fusion (ICF) capsule having a hypothetical yield of 3 GJ with an overall target gain in the range of 50-100. In the present paper, a combination of analytic arguments, results of radiation-hydrodynamic computational simulations, and empirical scalings from Z-pinch hohlraum experiments are used to demonstrate that the absorption of approximately 6 MJ of X-ray energy by the capsule and 26 MJ by the hohlraum walls of an ICF target (~ 32 MJ total X-ray input) will be adequate to provide a 3 GJ yield. As a result, it appears that the Ref. 1 assumption of a 3 GJ thermonuclear yield with an overall target gain approaching 100 is conceptually feasible.