In the use of solar panels, the energy source produced by the sun is converted into electrical energy and can be used directly by the user. However, in its use, solar panels have one weakness, namely dependence on the intensity of sunlight at that location. Therefore, it is necessary to be equipped with an electric charge storage device or battery to store electric charge when the area is not exposed to sunlight or at night. Determination of the correct storage capacity of the battery or battery is necessary to save costs, storage time, and battery or battery storage space. This study aims to determine the optimum battery storage capacity for a polycrystalline solar panel mounted on the housetop for 12 hours. In this study, the design of the solar panel structure mounted on the housetop was carried out and observed the value of the output current and voltage generated from three polycrystalline solar panels. Based on the research data, the average value of the output current from the solar panel for 12 hours is 0.28 A. The value of the energy charge from the solar panel generated for 12 hours stored in the battery is 3.32 Ah. Based on these data, it can be concluded that to store a source of electrical energy from a solar panel, a battery with a capacity of 5 Ah is needed. Determining the right battery capacity can store more power generated by solar panels and can be used to meet electricity needs when there is no sun exposure on solar panels.