The increasing limitations on available energy require use of new environmentally friendly resources and enhancement of utilization efficiency of available resources. Energy storage systems (ESSs) are a promising technology to realize such a goal; however, their application in networks requires an investment that must be economically justified. This study examined the effect of ESS use on energy generation costs in networks for a specific time period. This includes determining the best location for installation of the ESS and the best possible operation schedules for the ESS and power plants to achieve the greatest decrease in daily energy generation costs. The influences of all the factors affecting the final solution were studied under different scenarios. The effects of power plant cost functions, transmission line capacity, and network upgrades were compared. All scenarios were implemented in an IEEE standard 30-bus network. The best possible specifications of ESS can reduce daily energy generation cost by 3% for selected power plant cost functions. It was found that the use of ESS in a network uniformed stress on the transmission line and, in such a case, it would be possible to defer the network upgrade for 21 years.