In this written work will be presented the work and automatic start of the Čapljina hydro power plant, which belongs to reversible pumped-storage hydropower plants with own production flow. The power plant represents a significant reserve in the electric power system, it means that it is possible to regulate the system in the amount of 840 MW. At the time of commissioning, it's produced more than 50% of the power of all hydroelectric power plants in Bosnian Herzegovinians energy system. In addition to working as a classical hydroelectric power plant, in low-load hours in the electric power system, it takes over the surplus from flowing hydroelectric power plants, thermal power plants and nuclear power plants. Electricity of lower tariffs in hours when it works drive into peak, at energy the more tariffs, in the turbine. This achieves the expected effects in the electric power system, i.e. the need to build new power plants and increase the usefulness of the system is reduced.