PROBLEM TO BE SOLVED: To provide a method for determining equipment of a cogeneration system, an equipment determination device, an equipment determination program, and a computer-readable recording medium capable of suppressing a decrease in efficiency of the entire system. SOLUTION: A method of determining equipment of a cogeneration system CS is based on an hourly unit hot water supply load according to hot water supply usage by a plurality of consumers, and a total daily hot water supply load is set over a predetermined period longer than a specific period. Calculated, set at least a specific period on the low load side of the calculated daily total hot water supply load as the representative period, and determine the capacity of the cogeneration equipment C based on the total hot water supply load in the set representative period. Of the unit hot water supply loads for each of the two or more divided periods constituting the set representative period, the capacities of the plurality of hot water storage tanks are determined based on the hot water supply load that exceeds the capacity of the determined cogeneration equipment C. [Selection diagram] Fig. 1
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