The feasibility and economic worth of the Low Heat Rejection Engine (LHRE) are being studied for applications to the commercial truck market. Naturally, customer acceptance will be dependent upon the overall life cycle cost (LCC). Estimation of LCC is a lengthy, complex effort for current production engines, and has been even more difficult for new engine concepts for which there is no field experience. As part of a larger program to study the LHRE, a LCC methodology has been developed to quickly assess the economic worth of various LHRE concepts and configurations relative to the current state-of-the-art. The LCC model accounts for three major contributing elements; namely initial cost, fuel usage and maintenance. A model for each of these elements is developed, accounting for the significant influential parameters. All possible combinations of various LHRE and exhaust energy recovery system (EERS) concepts under study were analyzed. The best candidate LHRE configurations under minimum and mean LCC, and maximum LHRE benefit scenarios have been identified: these show the relative merits of various levels of LHR technology. LCC sensitivity to the major influential parameters has also been quantified.