Triboelectric nanogenerators (TENGs) have emerged as a promising technology to harvest electrical energy from natural motions such as human movement, wind, and water flow. Although TENGs show significant potential in small-scale applications, developing large-scale TENGs capable of generating high power remains a significant challenge. Several factors that can affect the performance of large-scale TENGs are being investigated to overcome this challenge, including the size and configuration of dielectric materials. This study optimizes dielectrics regarding surface area, thickness, and multicell configuration to improve harvested electrical power density in large-scale TENGs. In the studies, glass fiber was used as the positive dielectric, and multi-purpose white silicone was used as the negative dielectric because of their high tribo-potential, durability, and easy accessibility. In the size optimization phase, dielectric thicknesses and surface areas that provide the maximum power density were determined. Subsequently, horizontal and vertical multicell configurations were examined to efficiently integrate size-optimized dielectrics. The results reveal that large-scale TENGs with vertical multicell configurations can achieve high and usable energy density for electronics. The findings provide valuable insight into the development of large-scale TENGs with advanced power generation capabilities.