The all-vanadium redox-flow battery is a promising candidate for load leveling and seasonal energy storage in small grids and stand-alone photovoltaic systems. The reversible cell voltage of 1.3 to 1.4V in the charged state allows the use of inexpensive active and structural materials. In this work, studies on the performance of inexpensive active materials for use in vanadium redox-flow batteries are reported. Additionally, a cost analysis for a load leveling and a seasonal energy storage system is given based on a flow battery technology well established in Zn-flow batteries.