Energy storage through pumped-storage (PSP) hydropower plants is currently the only mature large-scale electricity storage solution with a global installed capacity of over 100 GW. The objective of this study is to evaluate the possibility of using this storage solution on a smaller scale to provide local voltage control and line congestion management to active medium-voltage distribution networks. First, several potential sites were identified in the French-speaking part of Switzerland, ideally with existing reservoirs. Following a selection of the most promising sites, two are selected to pre-size the various components and estimate the investment costs. These two sites are located in the Val de Bagnes in the canton of Valais in Switzerland and offer hydraulic powers of approximately 5 and 10 MW. The approximation of the investment cost is around 2 CHF/W. In comparison with recent large hydropower projects these prices seem quite reasonable, given that the investment cost for large hydropower is on the order of 2-3 CHF/W. In parallel, a free software ("freeware") program to evaluate the potential, to select the components and to estimate the costs is developed to facilitate future studies.