In this paper, a complete new methodology for the automated design of power-line filters is presented and tested. It is based on rigorous characterizations of power-line-filter components, devices under test, and line-impedance stabilization networks (or power-line networks) by means of -parameter and interference measurements. The implemented automated design tool is able to find an optimal power-line filter for a given device under test under constraints such as cost or number of components, drastically reducing the design time as compared to the usual trial-and-error practice. Since the features of common-mode chokes are highly dependent on the 50-Hz current levels flowing through them, a measurement system of common-mode chokes under 50-Hz load conditions has also been developed and tested in order to complement the automated design tool. The whole system has been successfully validated by means of experimental measurements.