NOVELTY - Invention is related to the field of autonomous power supply systems (APSS) for certain objects remote from power transmission lines, namely to APSS, which include renewable sources of energy as external source of electric energy, electrochemical generator (ECG), electrolytic cell and balloons for storage of reagents (hydrogen and oxygen). According to invention, autonomous power supply system comprises external source of electric energy, connected by supply buses to electric energy consumer, electrochemical generator based on fuel elements, electrolytic cell, hydrogen and oxygen balloons, connected by means of pipelines and valves to appropriate gas cavities of fuel elements in electrochemical generator and electrolytic cell and equipped with detectors of upper and lower permissible limit values of pressure, heat exchanger, coolant reservoir, circulating pump, at the same time fuel elements of electrochemical generator and electrolytic cell have common circuit of coolant circulation, it comprises: controller of coolant flow rate, inlet of which is connected to outlet of circulating pump, and one outlet is connected to inlet of coolant to electrolytic cell, the other one - to inlet of coolant to electrochemical generator, electronic converter, which provides for collection of electric energy by consumer from electrochemical generator, electronic converter, which provides for power collection by electrolytic cell, circuit of heat removal with additional circulating pump, mixer, one inlet of which is connected to common circulation circuit, and the other - to circuit of heat removal, and outlet of mixer is connected to inlet to coolant reservoir, and also pump of water supply to electrolytic cell from coolant reservoir is introduced, at the same time on pipeline, which connects outlet of mixer to inlet of coolant reservoir, there is a temperature detector installed, which is connected to additional circulating pump, and heat exchanger is installed in circuit of heat removal, moreover, electrochemical generator and electrolytic cell are connected to supply buses via according electronic converters. Method for operation of autonomous power supply system includes periodic consumption of electric energy from external source for water decomposition into oxygen and hydrogen in electrolytic cell and release of electric energy as a result of chemical reaction of oxygen and hydrogen in electrochemical generator, at the same time in period of consumption of electric energy produced from external source, for water decomposition into oxygen and hydrogen in electrolytic cell they also use part of electric energy from capacity of electrochemical generator, and as electric energy is released as a result of chemical reaction of oxygen and hydrogen in electrochemical generator, part of this released electric energy is used for water decomposition into oxygen and hydrogen in electrolytic cell. Besides in period of consumption of electric energy produced from external source, for water decomposition into oxygen and hydrogen in electrolytic cell they also used from 2% to 10% of electrochemical generator power, and when electric energy is released as a result of chemical reaction of oxygen and hydrogen in electrochemical generator, part of this released energy from 2% to 10% of electrolytic cell capacity is used for water decomposition into oxygen and hydrogen.    USE - Power engineering.    ADVANTAGE - Lower power inputs and improved efficiency of APSS at transition modes, and improved resource and reliability of APSS operation. 3 cl, 1 dwg