The present work proposes the Vector Current (CV) analysis, as an adequate method to quantize the performance of linear voltage regulators. We apply this analysis on linear voltage regulators that use a Zener diode as a core element. So, CV measure is a function of the Zener and load currents. CV analysis is carried out on three different regulator circuits, including an improved Feedback-Transistor-Zener (FTZ) regulator, which uses a feedback network for overload protection. As a result, the CV analysis can measure the different performances of the tested regulators, illustrating that there is an increasing current efficiency when using an additional transistor as current driver. Moreover, the CV analysis is useful to determine the overload value required for the feedback network design, opening further uses for evaluating power efficiency in other current-control power devices.