With the rising penetration of intermittent renewable energy sources (RES) and their variable nature it has become a challenge for distribution grid operators to maintain voltage quality inside the permissible range. It requires the involvement of new distributed resources, such as energy storage devices, to smooth power fluctuations of RES and to avoid long-term voltage rises. To achieve the best results such devices should be located as close to the micro source as possible – behind the meter. Small, distributed energy storage devices could be used to increase self-consumption of generated energy inside microgrids, helping also to flatten the daily load curve of the electrical power system (EPS). This paper discusses the properties of selected energy storage technologies suitable for small-scale microgrids containing renewable energy sources. The properties of small Zinc Bromine (ZnBr) flow batteries obtained in experimental research have been presented and compared to the properties of other energy storage devices similarly classified but at a different level of development. The simple equivalent model of the ZnBr battery has also been developed and described.