A apparatus may extract temperature for each region of a feed water and steam system of a thermoelectric power plant with respect to a combustible combination including one or more combustibles, extract one or more vectors for each region from the temperatures extracted for each region, generate one or more combustible clusters, each cluster including one or more combustible combinations having similar properties from the extracted vectors, and extract a characteristic component of a combustible combination that increases or decreases a boiler performance index from among one or more combustible combinations included in the one or more combustible clusters.