A system for producing hydrogen gas comprising: a heat exchanger module; the heat exchanger comprising: a warming module; and a boiler; a converter module; the converter module comprising a superheater, vaporizer, and/or compressor; an electrolyzer in communication with the converter module; and the electrolyzer in communication with the heat exchanger module. A method for producing hydrogen gas comprising: passing a working fluid into a heat exchanger module comprising warming module and a boiler to form a vapor-phase working fluid; passing the vapor-phase working fluid into a converter module comprising a superheater, vaporizer, and/or compressor to form a converted working fluid; passing the converted working fluid into an electrolyzer to form hot hydrogen gas and hot oxygen gas; passing the hot oxygen gas and/or hot hydrogen gas into the heat exchanger module.