The purpose of this project was to construct and test an off-grid photovoltaic (PV) system in which the power from a solar array could be stored in a rechargeable battery and a flywheel motor generator assembly. The mechanical flywheel energy storage system would in turn effectively power a 12-volt DC appliance. The voltage and current of different steel flywheel thicknesses were measured versus time for two different load settings on a 12-volt DC fan. The energy efficiencies of the system for each flywheel size were then calculated by integrating the power versus time scatter plots. The off-grid PV system was found to be functional in storing and discharging power, especially during quick discharges. Although not the most efficient method of energy storage, this apparatus shows great promise for energy storage when further tested and improved. (Contains 3 figures and 1 table.)