Electric energy, which is the main input of the growing world economy, depending on the consumption of the rapidly increasing world population and the devices fed with this energy, have become more indispensable in our lives with each passing day. In the consumption of electrical energy, determining the voltage level plays an important role in planning distribution systems that will directly affect consumers. Distribution systems in our country have been established at different levels for technical and financial reasons. Incorrect choices that can be made during the determination of the voltage level in distribution systems may increase energy unit costs and network losses, and may cause insulation and reliability problems. The aim of this study is to determine the optimum voltage level in distribution systems. A pilot region was determined for a local electricity distribution network in our country, and modeling and analysis were carried out at different voltage levels in the region with the help of a numerical analysis program. According to the results achieved, Insulation and reliability problems at low voltages are few and economic in terms of investment costs, but it has been observed that the operating load and cost are high due to high network losses. In high voltages, although the operating burden and cost are relatively low, it has been observed that the investment costs are high and the isolation and reliability problems are high.   Keywords: cost; distribution; investment; operating ;Voltage