In electrical systems, insulators play a crucial role in preventing leakage currents and maintaining voltage stability between high-potential components. Currently, most insulator materials are still produced from non-renewable sources such as Feldspar mineral rocks. The aim of this research is to determine the optimal breakdown voltage value based on variations in eggshell and resin compositions as binding agents, as well as to identify the best composition that supports production efficiency. The method used in this study includes calculating the initial composition with a simple proportional method, in which density per unit ratio is observed based on the initial composition, followed by breakdown voltage simulation using Python software on five sample variations of insulator material composition. Simulation results indicate that increasing the percentage of eggshell tends to increase the breakdown voltage value. The composition of 70% eggshell and 30% resin shows the highest estimated voltage at 93.33 kV. However, based on the study, this composition is still less optimal in terms of production feasibility because the insulator tends to have a rough texture and lacks hydrophobic properties.The composition of 47.5% eggshell and 52.5% resin demonstrates a balance in dielectric performance, with an estimated breakdown voltage of 63.33 kV, while also offering advantages in molding and production ease. Meanwhile, the 60/40 composition as the initial baseline shows results that can be considered a good choice, since it performs adequately both mechanically and electrically. These findings indicate that eggshell-based composite materials have potential as an environmentally friendly alternative insulator with efficient production processes.