In addition to the existing optimal design method of thermal-energy storage (TES) for industrial boiler plants, 2 new methods are put forward in this paper to achieve energy conservation. The 3 methods are based on minimization of TES capacity, optimization of load assignment, and minimization of the life-cycle cost (LCC) of a boiler plant equipped with TES, respectively. Modeling of the problems is introduced in the paper. A comprehensive computer program is completed, embodying 3 main modules corresponding to the 3 methods. The results of a computation example show that there are obvious differences between the 3 methods. The least initial investment in TES is obtained by the existing method, and the maximum energy saving results from the 2nd method, while the minimum LCC method is the most economic in over the life cycle. The program is useful in obtaining basic data necessary for decision making at the design stages of TES projects. (c) 2005 Elsevier Ltd. All rights reserved.