The paper presents possibilities to determine the factors that influence the availability of hydro aggregates. The case study presented in the paper is focused on the hydro–energy units from the Remeți and Munteni hydroelectric power plants belonging to Bihor Power System. The analyzed performance indicators refer to the specific activities of electricity production, respectively the management and exploitation of hydro aggregates at the maximum allowed capacity, as well as the specific activities of the system service, respectively the coordination of operation to meet the demand of National Power System. The purpose is to determine, respectively analyze, the availability coefficient (POF) respectively unavailability (UOF) and the cost of maintenance over a certain period of time.

Keywords: hydro-energy units, availability, cost-maintenance