SUBSTANCE: invention relates to design of autonomous tidal low-power damless power plants and can be used to convert energy of sea currents (tides) into electric energy. Proposed hydroelectric power plant (HPP) is intended for mass use as individual separate consumers and small settlements remote from main electric networks. Automatic tidal hydroelectric power plant with water reservoir includes inlet pressure tank 1, intermediate pressure tank 2 and storage tank 3 located near reservoir 4 on the coast and having height above level of tide located at the bottom of water reservoir near coast. Inlet container 1 has hole 5 for free passage of water in its bottom part, and bottom holes of intermediate tank 2 are equipped with two check valves 8 and 10 installed on inlet and outlet of water from this reservoir. In storage container 3 there is hole 11 also in bottom part connected with check valve 10 of intermediate container 2 to water inlet. Besides, accumulation tank 3 has overflow hole 12 in its upper part, connected through pipeline 13 to reservoir 4, wherein 1 and intermediate tanks 2 in their upper part are also connected by pipe 6. Hydraulic turbine 15 connected to electric generator 16 is connected to water reservoir 4. At present, vast territories of tidal zones of seas and oceans are not used in power engineering. This is related, among other things, with the need to select territories with availability of convenient places for construction of dams, which partition off bays or river mouths. Proposed self-contained Automatic tidal hydroelectric power station with water reservoir can be constructed irrespective of presence of these conditions practically on any coast of water reservoirs. HPP operates in automatic mode at filling of accumulator tank or small water reservoir for household needs and does not require personnel for permanent maintenance. EFFECT: hydroelectric power plant is assembled from serial units and structures, therefore, it has minimum cost at its construction that allows recommending it for wide application.