Systems, methods, and program product to synthesize a grass-roots heat exchanger network for hot process streams to be cooled and cold process streams to be heated and to identify optimal topology for future retrofit, are provided. An exemplary system includes a heat exchange network synthesizing computer and heat exchange network synthesizing program product configured to analyze the waste heat recovery problem, without decomposition, to produce a result having a better number of heat exchanger units and/or better waste heat recovery through application of advanced process-to-process matching schemes for both non-constrained and non-thermodynamically constrained problems. The heat exchange network synthesizing program product is also configured to produce alternative optimal heat exchanger network designs which account for variations in energy and capital costs to allow for construction of a physical heat exchanger network configured during its initial construction or deployment to be “easily-retrofitable” in future times according to a continuum of possible energy-capital cost scenarios.