A system, methods, and user-friendly program product to optimize energy recovery for a process or cluster of processes under all possible combinations of given process changes and stream-specific minimum temperature approach values without enumeration, are provided. The systems, methods, and program product can include steps / operations to identify an optimal set of discrete target temperature values for the process streams for a given heat exchanger network design, to identify which target temperature values of the various process streams have the most significant economic impact on the process or cluster of processes, and to identify process stream supply attribute ranges of variations, e.g., in the form of a criticality list for the plurality of process streams, e.g., resulting from disturbances and / or uncertainty, which have a highly significant or otherwise critical effect on streams target temperature.