A new analytical solution for the total power radiated by a single-wire line over a ground-plane is here proposed, for the special case of a lossless complex exponential current-distribution. The line is not assumed to be electrically short or “closed”, thus being suitable for assessing the emission/immunity of actual transmission lines as in the automotive domain. A practical procedure employing this model is proposed and it is shown to excellently agree with the experimental results obtained in a mode-stirred reverberation chamber. An application to unshielded multi-conductor transmission lines (MTL) is also proposed.